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Doctoral dissertation
To be presented by permission of the Faculty of Medicine of the University of Kuopio
for public examination in Auditorium L22, Snellmania building, University of Kuopio,
on Saturday 19th September 2009, at 12 noon
Faculty of MedicineInstitute of Biomedicine, Department of Physiology
University of Kuopio
FARSHAD DALILI
Pain Perception at DifferentStages of Orthodontic Treatment
JOKAKUOPIO 2009
KUOPION YLIOPISTON JULKAISUJA D. LÄÄKETIEDE 452KUOPIO UNIVERSITY PUBLICATIONS D. MEDICAL SCIENCES 452
Distributor : Kuopio University Library P.O. Box 1627 FI-70211 KUOPIO FINLAND Tel. +358 40 355 3430 Fax +358 17 163 410 www.uku.fi/kirjasto/julkaisutoiminta/julkmyyn.shtml
Series Editors: Professor Esko Alhava, M.D., Ph.D. Institute of Clinical Medicine, Department of Surgery Professor Raimo Sulkava, M.D., Ph.D. School of Public Health and Clinical Nutrition Professor Markku Tammi, M.D., Ph.D. Institute of Biomedicine, Department of Anatomy
Author´s address: Sii l injärvi and Maaninka, Health Centre Department of Dentistry Kasurilantie 3 FI-71850 SIILINJÄRVI FINLAND
Supervisors: Professor Matti Närhi, DDS., Ph.D. Institute of Biomedicine, Physiology Section University of Kuopio
Professor T. Maija Laine-Alava, DDS., M.Sc., Ph.D. Secretary General, Finnish Dental Society Helsinki
Reviewers: Professor Will iam Proffit , DDS., M.Sc., Ph.D. School of Dentistry, University of North Carolina, Chapel Hil l , North Carolina, U.S.A.
Professor Mauno Könönen, DDS., M.Sc., Ph.D. School of Dentistry, Department of Physiology and Prosthetics University of Helsinki
Opponent: Professor Timo Peltomäki, DDS., M.Sc., Ph.D. School of Dentistry, Department of Orthodontics and Pediatric Dentistry University of Zurich, Switzerland
ISBN 978-951-27-1172-7ISBN 978-951-27-1209-0 (PDF)ISSN 1235-0303
KopijyväKuopio 2009Finland
Dalili, Farshad. Pain perception at different stages of orthodontic treatment. Kuopio University Publications D. Medical Sciences 452. 2009. 99 p. ISBN 978-951-27-1172-7 ISBN 978-951-27-1209-0 (PDF) ISSN 1235-0303 ABSTRACT The purpose of the present study was to assess pain experience as reported by the patients during different stages of orthodontic treatment. Further, the aim was to examine the extent of which the sensitivity of the dental pulp might be affected by orthodontic treatment and if such changes could explain the mechanisms and origins of the pain symptoms. The study group consisted of 64 voluntary patients, 46 females and 18 males, with a mean age of 26.4 (SD 11.1) years. Patients were requested to fill out a structured questionnaire for three consecutive days after the insertion of orthodontic separators, after the initial archwire placement, and after the archwire activation. The intensity (mild, moderate, severe), quality (sore, shooting, dull, ache) and the duration (short, long) of the pain symptoms in connection with seven items were evaluated, namely: eating sweets, having hot or cold food/drink, tooth brushing, mastication of food, fitting anterior and fitting posterior teeth together. Clinical study regarding tooth sensitivity included measurements of the electrical thresholds with a constant current stimulator and cold sensitivity with an electrothermal device at 0ºC and 15ºC. A 100 mm Visual Analogue Scale (VAS) was used to assess the intensity of the cold responses to cold. Tooth movement/s were measured using the irregularity index (Little 1975) for the anterior teeth (canine to canine), in addition to tooth movements (mm) into the extraction spaces after three months of orthodontic force application. Proportion of the patients who had experienced pain was 70% after insertion of the separators, 96% after placement of the initial archwire and 69% after archwire activation, with the highest proportions during the first day after each procedure. The intensity of pain was mostly reported to be mild 62.5%, followed by moderate 28.5% and severe 9%, respectively. Regarding the quality the sensory experience was described as sore, shooting, dull and ache in 63.5%, 14.3%, 14.3% and 7.9% of the reports, respectively. Duration of pain was mostly short, in 85% of the sample. Regarding the listed items, mastication of food, fitting anterior and posterior teeth together, tooth brushing, cold and hot food/drink and sweets, in descending order, gave the most frequent pain reports. Dental electrical thresholds were generally unchanged before, during and after different orthodontic procedures. Proportion of teeth responding to the cold sensitivity tests as well as the intensity of the pain responses were higher at 0ºC than 15ºC, and were associated with the pain experienced at different stages of orthodontic treatment. In general the differences in the prevalence of the pain and the tooth movement with regards to anterior crowding, between the two different fixed orthodontic appliances were small. However, there was a difference in tooth movements into extraction spaces between the two fixed orthodontic appliances. It is concluded that 1) pain symptoms are common and the prevalence of such experiences varies at different stages of orthodontic treatment, insertion of the initial archwire being the most painful stage, 2) the intensity of the experienced pain was mostly mild followed by moderate pain reports and less frequently severe pain, 3) the induced pain is mostly due to periodontal nociceptor responses which is reflected by the frequent pain reports during mastication and fitting teeth together, 4) increased dental sensitivity to cold due to sensitization of the pulpal nerves suggests also pulpal involvement which seems to partly explain the origin of the pain symptoms in connection with orthodontic treatment, and finally 5) slight differences in the applied forces, due to the use of different initial archwires, provoked no apparent increase either in the pain experienced by the patients or in the dental sensitivity.
National Library of Medicine Classification: WU 400, WL 704 Medical Subject Headings: Dentistry; Orthodontics; Tooth Movement; Pain; Facial Pain; Toothache; Analgesia; Pain Measurement; Questionnaires
ACKNOWLEDGMENTS I would like to express my deepest gratitude to the supervisors of this study, Professor Matti Närhi DDS., Ph.D., for his discerning professional advice in many theoretical and practical matters. He always has had time for my questions and guided this work with warmth and supporting encouragement. My sincere thanks to Professor T. Maija. Laine-Alava DDS., MSc., Ph.D., for the supporting optimism and professional guidance until the end. Helping me realize the importance of pain control in orthodontics. I wish to extend appreciations to Professor William Proffit DDS., MSc., Ph.D., of the University of North Carolina, USA, the official reviewer of this study who blessed me with his constructive comments and criticism of the manuscript. My thanks to Professor Mauno Könönen DDS., Ph.D., of the University of Helsinki, the official reviewer for his constructive comments. This study was carried out at the Departments of Orthodontics and Physiology of University of Kuopio and at the Department of Oral Development and Orthodontics, Institute of Dentistry, University of Turku, and finalized at the Institute of Biomedicine, Physiology Section, University of Kuopio, Finland. I am grateful to Professor Juha Varrela DDS., MSc., Ph.D., Head of the Department of Oral Development and Orthodontics of University of Turku, Finland, for his support. To the personnel of the Orthodontic Department and all the patients and their parents who volunteered to participate in this study I owe my warmest thanks. The orthodontic materials of this work have been supported partly by Ormco and GAC international, which I acknowledge with gratitude. Many thanks to Dr. Anthony Viazis DDS., MSc., of Dallas, Texas, USA, for introduction of his approach to fixed orthodontic therapy. My thanks to Seppo Lammi, Head of the Department of Computer Sciences of the University of Kuopio for his guidance and advice with the statistical analyses. I owe my special thanks to Riitta Myllykangas for all the efforts she has put in to this study. I wish to thank my teachers and colleagues at the University of Kuopio for their support. Dr. Veijo Miettinen former head of the Dental Clinic, acting Professor Dr. Pauli kilpeläinen Ph.D., Dr. Armando Gale Associate professor, Dr. Riitta Pahkala Ph.D., Associate professor. Many thanks to my dear family for their loving support during this work. To my lovely sons Niku and Sam who have provided me with the encouragement for all strivings in my life. I owe my warmest thanks to my dear wife Dr. Najin Atashkari DDS., MSc., who has been strongest supporter of this study by taking care of every other detail in our lives to provide me the precious time I needed to finalize this research. September 2009, Farshad Dalili
CONTENTS ACKNOWLEDGMENTS 1. INTRODUCTION 2. REVIEW OF LITERATURE 2.1. Mechanism of the pain symptoms related to orthodontic treatment 2.2. Optimal forces for tooth movements 2.3. Dental pulp reactions to orthodontic forces 2.4. Variation of the perceived orthodontic pain with age and gender 2.5. Measurement of tooth sensitivity 2.6. Management of orthodontic pain 3. AIMS OF THE PRESENT STUDY 4. SUBJECTS AND METHODS 4.1. Subjects 4.2. Orthodontic mechanotherapies used for the study subjects 4.3. The questionnaire 4.4. Clinical examination 4.4.1. Dental electrical threshold measurement 4.4.2. Testing thermal sensitivity of the teeth 4.5. Measurement of tooth movement from hard stone casts 4.6. Study protocol 4.7. Statistical methods 5. RESULTS 5.1. Subjective pain experience during orthodontic treatment as reported in
the questionnaires 5.1.1. Prevalence of the pain 5.1.2. The intensity, quality and duration of the pain 5.1.3. Pain experienced during the three days subsequent to each orthodontic procedures 5.1.4. Pain experienced in relation to different stimuli of the questionnaire 5.1.5. The relationship between subjective pain reports and the analgesic consumption 5.1.6. Relationship between subjective pain reports and age, gender, extraction(s) and the extent of treatment 5.2. Clinical study 5.2.1. Responses to cold stimulation 5.2.1.1. Correlations between the VAS ratings to cold stimulation at
0 and 15ºC
5.3. Comparison of two different orthodontic mechanotherapies 5.3.1. Dental cold sensitivity and electrical thresholds in two different orthodontic mechanotherapies 5.3.2. Tooth movements in two different orthodontic mechanotherapies 6. DISCUSSION 6.1. Study subjects 6.2. Measurement of the experienced pain 6.2.1. The questionnaire 6.2.2. Subjective pain symptoms related to different orthodontic procedures 6.2.3. Intensity, quality and duration of the pain symptoms 6.2.4. Analgesic consumption 6.2.5. Dental pain sites 6.2.6. The relationships between the pain symptoms during initial tooth movement and age, gender, and treatment approach 6.3. Clinical study 6.3.1. Electrical tooth stimulation 6.3.2. Cold sensitivity tests 6.3.3. Comparison of different fixed oerthdontic appliances 7. SUMMARY AND CONCLUSIONS REFERENCES APPENDIX
1. INTRODUCTION
Pain is perhaps even older than mankind. There is a reason to believe that it is inherent in any life
linked with consciousness. Evidence indicates that man has suffered this affliction since his
beginning, for one finds testimony to the existence of pain in the chronicles of all races (Fulöp-
Miller 1938). The international Association of the Study of Pain has defined pain as: “an
unpleasant sensory and emotional experience associated with actual or potential tissue damage or
described in terms of such damage” (Wall and Melzack 1994).
Accordingly, pain is a complex experience that includes sensations evoked by noxious stimuli and
the reactions to such stimuli. The subjective reactions vary among individuals and can depend on a
person’s cultural background, past experiences, and other forms of psychologic input that give
meaning to a situation in which pain occurs (Burstone 1985).
Pain and pain control are important to dental profession, since general perception of public is that
dental treatment and pain are inseparable and go hand in hand. Orthodontic tooth movement
requires application of force to the tooth, which generally causes pain (Walker et al. 1987) although
not much knowledge exists on the intensity and quality of such pain symptoms. Because of its
obvious importance in orthodontics, one would assume a large volume of research on the treatment
of the related pain, which unfortunately is not the case. The intensity of the pain symptoms has been
studied to some extent (Tayer and Burek 1981, Ngan et al. 1989 and 1994, Brown and Moerenhout
1991, Jones and Chan 1992, Scheurer et al. 1996). However, there is little knowledge on the quality
and duration of such symptoms and their significance regarding the treatment.
The discomfort related to tooth movement is a subject little discussed by clinicians and given little
attention in orthodontics. There are reports that one of the discouraging factors for seeking
orthodontic treatment is the individual’s fear for the related pain and discomfort (Oliver and Knap-
man 1985). In most cases, the quality and extent of the information about orthodontic treatment and
the related discomfort seems to be satisfactory, but still many people report not having been well-
informed prior to the procedures (Oliver and Knapman 1985).
The control of pain in orthodontic therapy should include adjusting the forces to a level below the
pain thresholds. Unfortunately, such low forces would have very little if any effect on the tooth
movement. To alleviate the pain and discomfort clinicians have tried different approaches: a
conventional pharmacological analgesia (Simmons and Brandt 1992), physiologically by having
9
patients to chew on something fairly hard for example a plastic wafer (Furstman and Bernick 1972),
analgesic chewing gums (White 1984), transcutaneous electrical nerve stimulation (TENS, Roth
and Thrash 1986), low level laser therapy (Lim et al. 1995), and magnetic force fields (Blechman
1998).
The initial pain/discomfort experienced during orthodontic treatment for the first couple of days
after force application is a generally accepted observation. Many factors have been thought to affect
the extent of the symptoms, namely the intensity and duration of forces applied, age, gender, the
degree of crowding of the arch/es, patient’s psychological background and past experiences. There
is a traditional belief of the existence of a causal relationship between the amount of the force
applied to the tooth and the severity of the pain experience.
It seems to be a general assumption that the only sources for the pain in connection with orthodontic
treatment are the periodontal tissues or, more generally, tissues outside the tooth pulp. However,
many studies indicate that the pulp circulation and tissue metabolism and even vitality may be
affected or compromised by the applied forces (Butcher and Taylor 1952, Stenvik and Mjör 1970,
Biesterfield et al. 1979, Hamersky et al. 1980, Labat et al. 1980, Unterselher et al. 1987). Dental
electrical thresholds as an indicator of tooth vitality have been studied, however, not as a measure of
possible sensitivity changes in the pulpal nerves. The possible changes in the pulp nerve sensitivity
and their connection to orthodontic pain symptoms have evoked little attention.
Technological advances have long influenced orthodontic mechanotherapy approaches.
Introduction of superelastic, heat-activated archwires to orthodontics, claims to enable the
practitioner to reduce the treatment time by combining different stages of orthodontic treatment
done separately earlier, namely alignment, leveling and tooth movement (Viazis 1993, 1995, 1998).
The extent of which such approach might affect the type and amount of the tooth movement, the
perception of pain and discomfort experienced, and also the tooth responses, is not known. The
orthodontic profession needs critical clinical data on the relative efficiencies of different
biomechanical strategies of tooth movement. From a cost-benefit point of view, orthodontic
treatment should be performed as quickly as possible without jeopardizing the affected tissues. A
major question is which approach provides minimum discomfort, the most rapid orthodontic tooth
movement with the least damage to the teeth and the supporting structures.
10
2. REVIEW OF LITERATURE
2.1. Mechanism of the pain symptoms related to orthodontic treatment.
Nociceptive afferents transmit their messages to the central nervous system at different rates,
depending on the size and type of the axons. Both myelinated (A-type) and unmyelinated (C-type)
nerve fibers enter the pulp and periodontium (Reader and Foreman 1981, Holland and Robinson
1983, Byers 1984). A δ-fibers have diameters that vary between 2-4 and 20 microns with the
conduction velocity of upto 30 meters per second. A -fibers are present in somatic and visceral
nerves. They carry mechnoreceptive signals, pressure and proprioceptive impulses at the speed that
may exceed 100 meter per second. The unmyelinated C-fibers have a smaller diameter, up to 2
microns. Majority of them carry nociceptive signals but at a lower speed, approximately 0.5-2.5
meters per second.
Functional differences between, as well as their differences in the character of the tooth pain
associated with pulpal A- and C-fibers have been reported (Närhi 1985a, b, Jyväsjärvi and Kniffki
1987, Närhi et al. 1992a, b). Hydrodynamic mechanism, which is believed to activate A-fibers, is
most probably responsible for dentin sensitivity. C-fibers are activated by a direct effect of thermal,
mechanical and chemical irritants, for example, by bradykinin and histamine (Närhi 1985, Närhi et
al.1992). Heat stimulation induces an immediate sharp pain, which is due to A δ-fiber activation,
and a delayed dull pain indicative of C-fiber activity (Närhi et al. 1982a, 1984, Närhi 1985a,
Jyväsjärvi and Kniffki 1987). A δ-fibers are thought to be involved in the mediation of pain in the
initial phases of pulpal inflammation (sharp pain), the dull pain induced during the later phases is
probably due to C-fiber activation (Mumford 1982, Närhi 1985, Olgart 1985).
Release of neuropeptides has been suggested to be related to the activation of C-fibers and some
small diameter A δ-fibers (Byers et al. 1992b, Närhi et al. 1994, Byers and Närhi 1999).
Prostaglandins have been shown to increase intradental nociceptor sensitivity to thermal stimulation
and cause hyperalgesia (Ahlberg 1978) as do some other inflammatory mediators activated or
released in connection with tissue injury (Närhi et al. 1992, 1994). It is probable that inflammatory
reactions and nerve sensitization also take place in the periodontal tissues (Yamaguchi and Kasai
2005), although such responses in the PDL have been much less studied than the pulp nerve
reactions. Thus, tissue injury and consequent inflammation of gingival and periodontal tissues
during orthodontic treatment could lower pain threshold by inducing nociceptor sensitization. These
11
tissues may then become responsive to stimuli that would not ordinarily evoke any pain reaction
(Ngan 1994).
During orthodontic tooth movement the collagen fibers of periodontal ligament are disrupted, with
some part of the ligament undergoing compression and others tension. Initial healing of wounds in
the periodontal ligament begins with blood clot and granulation tissue formation subsequent to
necrosis regardless of the type of the periodontal challenge (Sismanidou et al. 1996). Organization
of granulation tissue follows, during which vascular and nervous components (Parlange and Sims
1993) as well as new periodontal connective tissue (Melcher 1970, 1976, Line et al. 1974, Caton
and Nyman 1980, Harison and Jurronsky 1991, Wikesjo et al. 1992) enter the area.
It has been suggested that the periodontal ligament nociceptive nerve fibers perform two main
functions: transmission of pain impulses centrally (Mengel, Jyväsjärvi and Kniffki 1992, 1993) and
release of neuropeptides peripherally (Davidovitch 1991). Närhi (1978) recording from the single
pulpal nerve fibers, found that an increase in the tissue pressure increases sensory nerve activity.
However, our knowledge regarding the function of the periodontal nociceptors is limited. It has
been shown, however, that they respond to strong forces applied to the tooth (Mengel, Jyväsjärvi
and Kniffki 1992, 1993). Khayat et al. (1988) suggested that after pulp tissue injury sprouting of the
nerve fibers in the pulp and apical periodontium might potentiate dental pain sensitivity by
multiplying the receptor sites.
The increase in the expression of Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP)
during the first two days after application of an orthodontic force in the rat (Kvinnsland et al. 1990,
Norevall et al. 1995) is interesting, considering the findings in clinical human studies that show pain
symptoms reaching the peak approximately one to two days after force application (Furstman and
Bernick 1972, Wilson et al. 1989, Ngan et al. 1989, 1994, Jones and Chan 1992).
Pain connected to orthodontic tooth movement most probably originates from the periodontal
tissues due to mechanical injury and consequent inflammatory reaction. However, also intradental
nociceptive nerves may be involved because periodontal inflammatory reactions may spread to the
pulp due to formation and diffusion of various inflammatory mediators, and neurogenic
inflammation mediated by branching axons, which are known to innervate both the pulp and
periodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b, Yamaguchi and Kasai 2005).
Moreover, as already mentioned, nerve sprouting also takes place within the pulp in response to
orthodontic forces, which may affect the functional properties of the intradental nerves. Also,
12
possible impairment of the pulpal blood flow due to vessel compression may play a role.
As already mentioned due to the neurogenic effects transmitted by branching axons innervating
both the pulp and PDL, the effects of periodontal tissue injury may also be reflected in the pulp. To
what extent pulpal inflammatory reactions and consequent increase in intradental nerve sensitivity
play a role in the pain responses to orthodontic tooth movement is not known.
2.2. Optimal forces for tooth movement
Many investigators have reported a relationship between the magnitude of applied force and
different types of tooth movement (Smith and Storey 1952, Reitan 1957, 1960, Burnstone and
groves 1961, Andreasen and Johnson 1967, Hixon et al. 1969, 1970, Mitchell et al. 1973,
Andreasen and Zwanziger 1980, Maltha et al. 1993, Owman-Moll et al. 1995, 1996, Bergius et al.
2002).
The term optimum orthodontic force is usually regarded as meaning the force that moves teeth most
rapidly, with the least discomfort to the patient and least damage to the teeth and their investing
tissues. In 1932 Schwarz stated that biologically the most favorable treatment is that which works
with forces not greater than the pressure in the blood capillaries. Oppenheim (1944) and Reitan
(1959) have also reported the optimal force levels based on capillary blood pressure in the
periodontal membrane. Schwartz (1932) in his experience, recommended light, continuous forces
because he was of the opinion that this prevents the formation of resorption-resistant osteoid bone
and certain reparative processes on the side toward which tooth moves. Burstone (1985)
characterized optimal force by maximal cellular response from the tooth supporting tissues,
including apposition and resorption of alveolar bone, at the same time as the maintenance of the
vitality of these tissues is secured. Thus, the amount of tooth movement is not the only indicator of
optimal force.
Light differential forces for tooth movement have been recommended, the assumption being that a
differential movement of the teeth can generally be achieved. Moreover, it is generally thought that
light forces are somewhat more efficient and more biologic and, hence, less painful (Storey and
Smith 1952, Reitan 1956). Reitan (1957, 1960, 1964, 1985) has always been a spokesman for light
forces, especially at the initial stages of tooth movement, to minimize adverse tissue reaction.
However, Hixon et al. (1969) found such a wide variation in response of individuals´ teeth to forces
applied that they suggested ideal light differential forces to be a myth. With respect to canine
13
retraction they found that higher forces were generally more efficient. Boester and Johnston (1974)
suggested that out of the three most common arguments favoring light forces, namely efficiency,
anchorage preservation and comfort, none could be substantiated in the exact sense of their original
proposal. Gianelly and Goldman (1971) questioned that larger forces cause greater periodontal
compression and result in greater pain. They also questioned the validity of using the pain response
as a guide to the amount of hyalinization of the periodontal ligament.
Yamaguchi and Nanda (1991, 1992) have shown that the same degree of forces results in varying
changes in blood flow and indicated that the change may be subject to deformation of the tissue but
not the degree of force. They concluded that tooth displacement has a closer relationship to the
decreased blood flow than to the degree of force.
Jones and Richmond (1985) have reported that the degree of crowding in the arches reflect the
overall forces being applied to the teeth in the arches examined, and demonstrated no correlation
between the magnitude of the force and the discomfort experienced. Owman-Moll et al. (1995) in a
clinical study showed that buccal tipping of maxillary first premolars was less efficiently performed
with an interrupted force than with a continuous one, and found no difference in the number or
severity of areas of root resorption between the two force systems. In an interrupted force system
with rest periods one would, however, assume less tissue strain and possibly more tooth movement
with less root resorption. Owman-Moll et al. (1996), and Bergius et al. (2008), suggested that
individual responses might have more impact than the increase in the amount of force or length of
experimental period on both the tooth movement achieved and occurrence of root resorption.
Generally, the use of light continuous force is thought to be the key factor for orthodontic tooth
movement. However, the connection between the different recommended ranges of such light
forces and the pain experience is not clear, and the picture seems to become more complex when
the type and amount of the tooth movement is considered.
2.3. Dental pulp reactions to orthodontic forces
The blood flowing through the tooth is confronted with a unique environment. The dental pulp is
incased within a rigid, non-compliant chamber and its survival is dependent on the blood circulation
and vessels that access the interior of the tooth through the apical foramen or multiple foramina
(Barwick and Ramsay 1996).
Understanding the effect of orthodontic force on the pulp is of particular importance, because it
14
interferes with pulpal circulation and, thus, the metabolic activity and the respiration rate of the pulp
tissue (Hamerski et al. 1980, Unterseher et al. 1987). The effects can be reflected as disruption of
the odontoblast layer (Stenvik and Mjör 1970, Anstendig and Kronman 1974), pulpal obliteration
by secondary dentin formation (Marshall 1933, Cywk et al. 1984), root resorption (Spurrier et al.
1990, King and Fischlschweiger 1982, Reitan 1964, Vardimon et al. 1991), and even pulpal
necrosis (Butcher and Taylor 1952, Cwyk et al. 1984, Årtun and Urbye 1988), which have all been
associated with orthodontic treatment. Additionally, the indirect effect of orthodontic forces through
neurogenic interactions may play an important role (Yamaguchi and Kasai 2005).
Reversible pulpal injury is a common response to orthodontic treatment (Stenvik and Mjör 1970,
Hamersky et al. 1980, Labat et al. 1980, Unterseher et al. 1987). Ikeda et al. (1998) monitoring
dental pain thresholds in response to electrical stimulation, demonstrated that light premature
contacts resulting in abnormal loading of teeth were capable of increasing tooth sensitivity, and that
after elimination of such interferences, tooth response returned to the base line and clinical
symptoms disappeared. In animal studies such an injury has been induced, and the severity of the
changes depends on the intensity and duration of the irritation and the resistance of the pulp
(Biesterfield, Taintor and Marsh 1979). Butcher and Taylor (1952) reported that experimental
retraction of the lower incisors with 250 gram of force for 3 to 20 days in rhesus monkey produced
early pulpal changes ranging from partial blood flow stasis to necrosis.
Intrusive forces have also been considered to have deleterious effects on teeth. Stanley et al. (1978)
suggested that a too powerful depressive force may shut off the arterial supply and thus produce
devitalization of the pulp. Stenvik and Mjör (1970) reported that with intrusive force on human
premolars for 4 to 35 days, the main pulpal changes were circulatory disturbances. Further, the
effects of traumatic occlusion and excessive stress of orthodontic forces have been reported to cause
extravasations of blood and necrosis of the pulp tissue in human teeth (Seltzer and Bender 1975).
Experimental data using respiratory activity (oxidation of organic fuels by molecular oxygen) as an
indicator of pulpal injury, have indicated that a 72-hour orthodontic force can cause a 27%
reduction of pulp metabolism in human premolars. The respiratory rates remained depressed for at
least one week after the force was discontinued. The metabolic effects were significantly smaller in
younger subjects with more patent root apices than in older people (Hamersky et al. 1980). One
factor contributing to this apparent decrease in respiration rate could be a strangulation of the blood
vessels and stasis of blood flow to the pulp (Marshall 1933, Orban 1936, Oppenheim 1937,
Stuteville 1938, Butcher and Taylor 1951, 1952, Langeland 1957, Anstending and Kronman 1974,
15
Guevara et al. 1977). Another interesting finding by Hamerski et al. (1980) was that as the age of
the subjects increased, the relative amount of depression in the pulpal respiratory rate also
increased. These results seem to indicate a relationship between the biologic effect of orthodontic
force and the maturity of the tooth. Accordingly, large apical foramina result in a reduction of
detrimental effects from orthodontic force.
Regulations of the blood flow by sensory nerve fibers, and the related neurogenic inflammatory
reactions have been described in the dental pulp (Gazelius et al. 1987, Olgart 1985, 1990).
Neurogenic inflammation effects include the release of vasoactive peptides from the nerve endings
and consequent vasodilation, increased vascular permeability and hyperalgesia. Furthermore, it has
been shown that sensory nerve fibers sprout in the inflamed pulp tissue, which may affect its
sensitivity (Kimberly and Byers 1988, Taylor et al.1988, Byers et al. 1990b, Michelotti et al. 1999,
Yamaguchi and Kasai 2005).
2.4. Variation of the perceived pain during orthodontic treatment with age and
gender
Relation of age and the perceived pain during orthodontic therapy is not clear, partly because a
critical comparison of the various studies is impossible due to differences in experimental designs
and methods.
Ngan (1989) found significant interaction between the age and duration of force implemented.
Patients 16 years of age and younger experienced more discomfort at 4 hours, whereas patients
older than 16 years of age experienced more discomfort at 24 hours and at the 7th day. Brown and
Moerenhout (1991), however, reported that adolescents of 14-17 years of age were more vulnerable
to the undesirable psychological effects of treatment and had higher levels of pain than younger and
older patients. Scheurer et al. (1996) also reported that 13-16 years old patients had the highest
prevalence of pain. Jones and Richmond (1984) have shown that adults experienced more pain than
adolescents, however, pain experiences do not appear to differ between the genders. Differences
between study designs and methodologies may partly explain these different conclusions. Ngan et
al. (1989) reported no difference in the perception of pain from orthodontic appliances between
males and females. According to Scheurer et al. (1996), however, girls reported a higher impact on
daily life, and significantly greater pain intensity and analgesic consumption than boys in response
to fixed appliances. The changes with age on the perceived pain may relate to the differences in the
tissue compliance and tissue repair. However, there is a wide range of individual variations in the
16
pain experienced during orthodontic treatment, which is affected, by patients past experiences,
cultural background and other forms of psychological input (Burstone 1985).
2.5. Measurement of tooth sensitivity
For the measurement of tooth sensitivity it is necessary that the stimulus intensity needed to evoke a
sensory response can be determined accurately and reliably. Different stimuli have been used for
the purpose. These include; mechanical, thermal, osmotic, dehydrating and electrical stimulation.
The sensitivity can be different depending on the type of stimuli used (Lilja 1980, Närhi 1985a,
Orchardson and Collins 1987b).
The measurement of tooth sensitivity during orthodontic treatment is technically complicated. On
one hand, bonding materials, brackets and archwires limit the accessibility to the tooth surface for
stimulation and, on the other hand, open dentinal tubules which may be the basis for pain induction
with some stimuli may not be found as often in orthodontic patients as in patients with, for example,
dentin hypersensitivity.
A preferred method of stimulating dental pulp for induction of pain is cold stimulation. It has been
found to be the most potent (Flynn et al. 1985, Orchardson and Collins 1987b) and also better
tolerated by dental pulp than for example hot stimuli (Pashley 1990). Fulling and Andreasen (1976)
reported consistent responses from the teeth, which had stainless steel crown using cold stimulation
with carbon dioxide snow. Electrical stimulation of the teeth was reliable only when the
stimulator’s electrode was directly in contact with the enamel, thus, controlling the electrical
current leakage.
The sensitivity of electric pulp testers for detection of different stages of pulpal inflammation has
been questioned (Seltzer et al. 1963, Mumford 1982). Nevertheless, higher accuracy in the
measurement of the applied stimulus by electrical rather than natural stimuli has been noted
(Mumford 1982). According to Närhi (1985) since electrical stimulation affects any excitable cell
membrane, it could as well activate intradental axons as peripheral receptors, and thus would not be
a valid measure of the pulpal nociceptor sensitivity.
Markus (1946) reported that teeth became more responsive to electric pulp testing immediately
following orthodontic activation while Burnside et al. (1974) found that in general the experimental
17
teeth showed higher pain threshold values to electrical stimulation than did the controls indicating
reduced sensitivity. It must be mentioned that in the study of Burnside et al. (1974) the comparison
was made between the orthodontic patients who had fixed orthodontic appliances for a minimum of
four months prior to the test, and the control group had no appliances. Longitudinal studies would
be needed to find out the effects of orthodontic tooth movement on the dental pulp sensitivity.
McGill Pain Questionnaire (MPQ) measures both the intensity and quality of pain. This verbal
rating scale has been used previously for evaluation of pain symptoms in orthodontics, and shown
to have high reliability (Brown and Moerenhout 1991). However, vocabulary limitations (Gracely et
al.1978) and insufficiency of pain-word questionnaires have been noted (Curro 1990). The Visual
Analogue Scale (VAS) is a direct pain intensity scaling method in which the subjects evaluate the
level of pain by making a mark on a continuous line. One end of the line means “no pain and the
other end “intolerable pain” es of using the VAS over
observational, self-report, behavioral, physiological or verbal rating scales, are the higher
sensitivity, reproducibility and reliability of the direct scaling techniques (Melzack, Torgerson
1971, Uskisson 1974, Scott and Huskisson 1979, Huskisson 1983, Seymour et al. 1985, McGrath
1986, Duncan et al. 1989). It also allows the use of parametric statistical tests (Bhat 1986). On the
other hand, the limitation of VAS is that the recorded values are mostly related to the intensity
component of pain.
( uskisson 1983). The advantag H
2.6. Management of orthodontic pain
Pain caused by orthodontic treatment can be a major negative component of the entire therapy.
Theoretically, the ideal way to control pain during orthodontic treatment would simply be to keep
the applied force levels to a minimum, below the pain threshold. This approach, however, is
contradictory for the purpose if the force levels should be kept too low to result in any tooth
movement (Simmons and Brandt 1992).
Conventional analgesics have been used to alleviate orthodontic pain. According to Simmons and
Brandt (1992) these drugs should be taken prior to the installation of an active orthodontic
appliance and for a minimum of 24 hours following the procedure. However, Ngan et al. (1994)
reported that single dose given at the moment of orthodontic appliance insertion was sufficient for
prevention of pain symptoms.
18
”
In addition to the conventional analgesics more physiological approaches for the treatment or
prevention of pain have been applied. Chewing something fairly hard -a plastic wafer, for example-
within the first two hours after arch wire adjustment may act to reduce the ischemia and
inflammation in the periodontal ligament (Furstman and Bernick 1972). Stimulation of vascular and
lymphatic circulation would prevent the build-up of metabolic products, which are known to
stimulate pain receptors (Proffit 1986).
In a study on 93 orthodontic patients, White (1984) found that 63% of their subjects reported less
discomfort after chewing analgesic gum, however, lack of control group in this study raises the
question of whether the reduction of pain was due to the analgesics or the chewing function.
Transcutaneous electrical nerve stimulation (TENS) is another technique for pain control in
orthodontics which according to Roth and Thrash (1986) dramatically decreased the delayed (more
than 12 hours after arch wire adjustment) pain response. Unfortunately, there was not any
significant reduction of pain within the first 12 hours using this method. Low level laser has been
claimed by many investigators to produce analgesic effects in various therapeutic and clinical
applications (Plog 1980, Midda and Renton-Harper 1991). The mechanism of laser analgesia has
not been established, but it has been attributed to its anti-inflammatory effects (Harris 1991). Low
level laser therapy has been applied for the treatment of pain related to orthodontic activations but
without success (Lim et al. 1995). Blechman (1998) reported of the possibility of pain free and
mobility free orthodontics using magnetic force fields. Magnetic field is hypothesized to accelerate
osteogenic rate and therefore, reduce tooth mobility and the related pain. However, the assumption
is based only on several reports by different clinicians. Up to date there is no systematic study
published comparing the pain experience, tooth mobility and sensitivity between the tooth
movements in the conventional approach and under magnetic fields. Further studies on the different
mechanisms of pain induction during tooth movement are needed to provide the essential
knowledge for its possible management.
19
3. AIMS OF THE PRESENT STUDY
The purpose of the present study was to assess the prevalence and significance of the pain
experience reported by the patients at different stages of orthodontic treatment. It was also
examined to what extent the dental pulp sensitivity might be changed or affected by the treatment,
and if such changes could explain part of the pain symptoms complained by patients. It was
hypothesized that the pain experienced during orthodontic tooth movement is strongest at the initial
phase of the therapy and that it gradually decreases with time. Also it was presumed that the amount
of tooth movement as a response to orthodontic forces is related to the tooth sensitivity as
perception of pain experienced by the patients.
The specific objectives were to study:
1. The prevalence, intensity, quality and duration of pain/discomfort experienced by patients at
different stages of orthodontic treatment during different functions used as stimuli, by using a
structured questionnaire,
2. The effect of orthodontic treatment/forces on electrical thresholds and cold sensitivity of the
dental pulp,
3. The relationship between the subjective pain perception as reported in the questionnaire and pain
responses in the clinical sensitivity tests,
4. The relation of the subjective pain perception and the clinically assessed sensitivity to the amount
of tooth movement.
20
4. SUBJECTS AND METHODS
4.1. Subjects
The study group consisted of 64 patients, 46 females and 18 males, with a mean age 26.4 years (SD
11.1). The distribution of the age and gender of the subjects is shown in Table 1.
Table 1. Age and gender distribution of the subjects.
Age (yrs) Female
(n=46)
Male
(n=18)
Total
(n=64)
Mean
SD
Range
27.8
11.7
10.8-49.3
22.9
9.0
11.8-40.6
26.4
11.2
10.8-49.3
The study subjects were not pre-selected but the sample was formed by consecutive cases from
patients who were willing to participate. Patients were included in this study at the beginning of
their active orthodontic treatment before the insertion of fixed appliances. The deciduous teeth of
patients who were in the late mixed dentition stage were not included in the measurements. The ap-
pliances inserted were complete banded/bonded appliance of either one or both dental arches. No
additional elements of fixed appliances, extraoral or functional appliances were used during the
study. The study protocol was approved by the ethics committee of the Medical Faculty, University
of Kuopio, Kuopio, Finland.
4.2. Orthodontic mechanotherapies used for the study subjects
Three different fixed appliances were used: Standard edgewise technique for six patients, Wick
Alexander technique for 30 patients and Viazis technique for 28 patients. Because of the small
number of participants in the standard edgewise bracket group (n=6), this group was not included in
the comparison of different techniques but for all other comparisons.
21
Elastics for separating the first molars before banding (3M Unitek, Alastik Separator Modules) were
placed and left at the mesial and distal contacts of the first permanent molars in each of the four
quadrants for a three day period.
The three different types of fixed appliances used a 0.018″ bracket slot size, were: the Viazis
(OrthoSystem Inc., Plano, TX), the Alexander MINI WICK (Ormco Corporation), and the Standard
edgewise (Unitek/3M) brackets. The characteristics of the different mechanotherapies in producing
orthodontic tooth movement have been described (Viazis 1995, 1998, Alexander 1986)
- Viazis Bioefficient therapy (Viazis 1995) with a triangular bracket design, which is a combination
of a twin bracket at the lower half and a single bracket type at the upper half. The bracket slot is
elevated so that the wire may come in contact with the extensions (the bracket elbows), thus
providing control for tipping movements. The longer the interslot distance, the lower the wire
stiffness. The Viazis mechanotherapy incorporated a square initial archwire, 0.018″ x 0.018″ Heat
activated, Ionguard (Nitrogen substitution of the top 3 μmm of Nickel of the archwire surface),
Bioforce Sentalloy (GAC International, Inc.). These archwires have been described to demonstrate
a differential force delivery increasing progressively from 80 grams of force anteriorly, up to 320
grams of force in the posterior region. Heat activated property refers to that a decrease in
temperature allows the archwire to be in the martensinic phase, which provides ease of handling
during the archwire engagement to the bracket. At the oral temperature, austensinic phase resumes
the original arch form (shape memory). Additionally, in this technique in premolar extraction cases
Niti closed coil springs, Tension w/hooks M (GAC International, Inc.) were used in conjunction
with the initial archwire. The closed coil delivers 150 grams of force for canine retraction (GAC
International, Inc.). The objective of this mechanotherapy is to start the space closure as soon as
possible and to make the transition towards the finishing stainless steel wire within four to six
months of active therapy.
- Alexander technique has a twin bracket design for the maxillary incisors in combination with
single brackets with wings on the rest of maxillary and mandibular dentition. A round 0.016″
Superelastic Thermalloy Niti initial archwire (RMO) was used. This archwire has been described to
have a force delivery of 80 grams of force throughout the arch (Alexander 1986). In both extraction
and non-extraction treatments it is recommended the initial archwire to be activated for the next two
or three appointments before changing to an archwire with higher forces, for example, a round
0.016″ stainless steel wire, to continue the alignment and leveling or the sliding mechanics for
canine retraction.
22
- Standard edgewise technique, incorporated the same initial archwire and mechanotherapy
approach as that of the Alexander technique, the difference being the types of the brackets used.
The age and gender distribution of the subjects in the Alexander technique (n=30) and the Viazis
(n=28) technique is shown in Table 2.
Table 2. Age and gender distribution of the subjects treated with the two different types of fixed
appliances.
Alexander technique Viazis technique
Age (yrs) Female
(n=23)
Male
(n=7)
Total
(n=30)
Female
(n=19)
Male
(n=9)
Total
(n=28)
Mean
SD
Range
28.8
11.3
10.8-45.9
27.4
9.5
12.3-40.6
28.5
10.7
10.8-45.9
25.9
11.6
11.4-45.4
21.5
7.9
11.8-33.2
24.5
10.6
11.4-45.4
4.3. The questionnaire
The intensity, quality and duration of pain symptoms subsequent to the placement and activation of
the orthodontic appliances were assessed in a longitudinal series of questionnaires. The question-
naires (Appendix I) were given to each patient with a request to return them for the next
appointment. The patients were given oral as well as written instructions on how to complete the
questionnaire. Neither prescription for pain medication nor analgesics were dispensed to the
patients. However, they were free to take any medication they felt necessary. They were asked to
mark at the top of the questionnaire the brand name, dose and timing of the medication they had
possibly taken. In the questionnaire the occurrence of pain in connection with seven different
stimuli related to everyday life was included, namely: cold food/drink, hot food/drink, sweets, tooth
brushing, mastication of food, fitting the anterior teeth together and fitting the posterior teeth to-
gether. The patients were requested to fill out the questionnaire every morning for three days after
insertion of orthodontic separators, after initial archwire insertion and after activation of the
23
archwire. The pain intensity was scored on a 0-3 scale on each of the first three days after the three
aforementioned stages of the orthodontic treatment (see protocol page 32). The scores were defined
as follows:
0 = No pain,
1 = Mild pain,
2 = Moderate pain,
3 = Severe/intolerable pain.
The descriptors which were used to indicate the quality of pain in the questionnaire were as follow;
1) sore, 2) shooting, 3) dull and 4) ache. Duration of pain was divided into two groups of short (S)
(lasting not more than a few seconds) and long (L) lasting pain (clearly outlasting the time of the
stimulus).
The pain experience related to each stimulus was estimated for its intensity, quality and duration
(Table. 3).
Stimulus Sore Shooting Dull Ache
Fitting
front teeth
together
0
1
2
3
Duration
S
L
0
1
2
3
Duration
S
L
0
1
2
3
Duration
S
L
0
1
2
3
Duration
S
L
Table 3. An example of a patient’s response to pain from fitting the front teeth together after the
insertion of the initial archwire. The patient reported that the teeth were sore and the evoked
sensation was mild and short lasting.
The intensity of pain related to each pain descriptor was calculated on the basis of all responses
given by the patients in all questionnaires and each stimuli. The mean values for each descriptor are
presented in Figure 1. Although not statistically significant, there was a clear trend, the order of the
intensity scores for different descriptors was: sore<shooting<dull<ache. Figure 2 shows the relation
between the intensity and the duration of the reported pain.
24
0
1
2
3
sore shooting dull ache
Quality of pain
Inte
nsity
of p
ain
Figure 1. The overall relations between the quality and the intensity of the reported pain.
0
1
2
3
short long
Duration of pain
Inte
nsity
of p
ain
(0-3
)
Figure 2. The relations between the overall intensity and duration of the reported pain.
25
On the basis of this comparison the pain quality descriptors were arranged in the following order
from the least intense to the most intense one; 1= sore, 2= shooting, 3= dull and 4= ache.
Correspondingly, pain described as being of either short or long duration was given values of 1 and
2, respectively. They were given these numerical values for the further analyses and used to form a
total pain score.
For statistical analyses, an index describing the pain experience was formed by multiplying the
numerical values of the intensity (0-3), the quality (1-4), and the duration (1, 2) of pain.
Thus the maximum pain scores were as follows:
1) 3 x 4 x 2=24 PIS Pain Index for each Stimuli (one questionnaire)
2) 24 x 7=168 PIQ Pain Index for one Questionnaire (seven stimulus)
3) 24 x 7 x 3=504 PIStage Pain Index for one treatment Stage (three questionnaires)
4) 24 x 6=144 PI2Stages Pain Index for each Stimuli at Two stages
(six questionnaires)
5) 24 x 9=216 TPIS Total Pain Index for each Stimuli at three stages
(nine questionnaires) 6) 24 x 7 x 9=1512 TPI Total Pain Index (seven stimuli and nine questionnaires)
4.4. Clinical examination
A total of 907 teeth of the 64 subjects were examined in the clinical sensitivity tests, which included
measurements of the dental electrical thresholds and cold sensitivity. The teeth were dried and
isolated with cotton rolls. The measurements were performed for each tooth starting from the
maxillary right first molar and ending up with the mandibular right first molar (maximum of 24
teeth per patient). Thus five to ten minutes of recovery period was allowed between stimulus appli-
cations for each tooth. Any enamel/dentin irregularities or caries/fillings were avoided as sites of
stimulation. The tooth number and the surface were noted on the patients´ chart so that the same
spot could be stimulated during all appointments. Teeth with crowns, root canal fillings and/or with
extensive fillings were excluded. If the molars were to be banded, they were excluded from the
sensitivity tests after banding due to the difficulties in finding an exact spot for stimulation. Thus
those cases were included only in the first set of the questionnaire involving the separation of the -
molar and patient’s response during the following three days. Altogether 5-7 hours was spent
collecting the data from each patient.
26
4.4.1. Dental electrical threshold measurement
Electrical thresholds were measured with a constant current electrical stimulator (Bofors Pulp
Tester, Bofors, Sweden) in µA, (Fig.3). The stimulator gives 10 ms cathodal square wave pulses at
5 Hz frequency. The stimulator tip was 2 mm in diameter and made of conductive rubber. The tip of
the stimulator was placed in contact with the incisal third of the lingual/palatal surfaces of the
incisors and lingual/palatal cusp tip of the premolars and the mesiolingual/palatal cusps of the first
molars (Fig. 4). Stimulation of the cervical third close to the gingiva was avoided because of the
danger of the current leakage to the soft tissues with low resistance (Mumford and Björn 1962,
Matthews and Searle 1974, 1976, Mumford 1982). Patients were instructed to stop the electrical
current by pushing the button on the handle as soon as they felt any sensation (prepain). The
electrical threshold of each tooth was measured twice, and the mean value of the two measurements
was used for further analysis of data. In cases in which the difference between the two readings was
more than 5 µA in incisors, 15 µA in canines and premolars and 25 µA in molars, the lower
values were selected.
27
Figure 3. The constant current electrical stimulator used to measure the dental electrical thresholds
(Bofors Pulp Tester, Bofors, Sweden).
Figure 4. The electrical stimulator probe in contact with the incisal third of the palatal surface of a
maxillary central incisor.
28
Figure 5. The thermal stimulator used to test the cold sensitivity of the studied teeth.
Figure 6. The cold stimulator probe in contact with the cervical third of the facial surface of a
maxillary lateral incisor.
29
4.4.2. Testing thermal sensitivity of the teeth
Methods for testing sensitivity of tooth, originally developed for studies on dentin hypersensitivity
(Kontturi-Närhi 1993, Kontturi-Närhi and Närhi 1993), were adopted for examination and evalu-
ation of the tooth responses to orthodontic forces. An electrothermal device constructed in the
Technical Center of the University of Kuopio was employed for the purpose (Fig.5). The
stimulator´s probe had a feedback circuit for the control of the tip temperature at an accuracy of
0.1ºC. The tip diameter was 2mm. Cold stimuli at 15ºC and 0ºC were applied to the teeth under
examination. The tip of the probe was precooled to the desired temperature and then placed on the
cervical third of the facial surface of each tooth (Fig. 6). In each stimulation trial the cold probe was
kept in contact with the tooth for a maximum of 2 seconds. No extra pressure was exerted on the
tooth surface. Prior to testing, patients were instructed to raise the right hand at the instant he/she
felt the first sensation. As soon as the patient gave a positive response, the stimulation of the tooth
was discontinued.
The intensity of the induced pain was assessed with a 100 mm Visual Analogue Scale (VAS)
(Huskisson 1983, McGrath 1986). The left end of the scale indicated "no pain" and the right end
"intolerable pain" (Fig. 7). Patients were requested to place a vertical mark on the VAS
corresponding to the intensity of the pain they experienced. They were able to see only one VAS at
a time.
The distance of the mark from the left end of the scale was then taken to represent the VAS pain
score.
No pain Intolerable pain
Fig. 7. The visual analogue scale (VAS) used in the present study. The length of the scale was 100
mm.
4.5. Measurement of tooth movement from hard stone casts
Dental casts were made from alginate impressions taken before the treatment and a second set three
months after the placement of the initial archwire. Severity of malocclusion was then measured
using the Irregularity Index, defined as the summed displacement of adjacent anatomic contact
30
points (Little 1975) for the maxillary and mandibular anterior segments (canine-canine).
Furthermore, in extraction cases the movement of the teeth moved into extraction space was
measured. The measurements were carried out with a Mitutoyo digital caliper (Mitutoyo Mfg. Co.,
Ltd., Japan) to the nearest 0.1 mm. For intraexaminer consistancy, the measurements included the
Irregularity Index as well as the amount of tooth movement into the extraction spaces, twenty
randomly selected dental casts were measured three times with a three weeks intervals. The
intraclass correlation coefficient (Selkäinaho 1983) was used for the three repeated measurements
of the dental casts. The values of ICC were high for both measurements (ICC 0.99, 95% CI 0.998,
.0999). There was no statistically significant difference between the two groups with regards to the
anterior crowding prior to the orthodontic treatment (by t-test).
31
4.6. Study protocol The examination of the subjects was divided into five stages (I-V) as shown in the following table:
Stage Orthodontic procedure Cold sensitivity and
electrical pulp tests
Questionnaire
I Orthodontic separators
(S)
Initial (T1), before
separation of molars
Three (one/day, S1, S2, S3)
II
(3 days after stage I)
Banding/Bonding &
initial archwire (W)
Second (T2) Three (one/day, W1, W2, W3)
III
(3 days after stage II)
Third (T3)
IV
(A month after stage III)
Before activation of the
archwire (A)
Fourth (T4) Three (one/day, A1, A2, A3)
V
(3 days after stage IV)
Final (TF)
T1 corresponds to the measurements of the cold sensitivity and electrical pulp tests, before the
insertion of orthodontic separators. T2 is the pulpal tests after three days of orthodontic separation of
molars. T3 is the pulpal tests after three days of bonding orthodontic appliances. T4 is the pulpal
tests before activation of archwires and TF is the final pulpal tests, three days after activation of
archwires.
32
4.7. Statistical methods
In analyzing data from the questionnaire, chi-square test and Z-test were applied in comparing the
frequencies of the categorical variables at different stages of orthodontic treatment. The Wilcoxon
matched-pairs signed-ranks test was used to compare the changes in the pain intensity (0-3), quality
(1-4) and duration (1,2), at different days (1,2,3) and stages (separation of the first molars, initial
archwire insertion and the archwire activation) of the orthodontic treatment. The differences
between the means of the parametric variables were analyzed by Student’s t-test. Pearson
correlation coefficient was used when analyzing the relationships between the clinical measurements
(cold sensitivity at 15ºC and 0ºC, electrical thresholds), and the subjective responses to the
different orthodontic procedures (separation of the first molars, initial archwire insertion and the
archwire activation). Multiple regression analysis was used to estimate the associations between the
scores of the index of the reported pain and clinical measurements for each tooth including cold
stimulation (VAS values in mm) and the electrical thresholds in µA, considering the possible
effects of age (years), gender (0=female, 1=male), type of brackets (1=Alexander, 2=Viazis) and the
use of analgesics (0=no, 1=yes), one or both jaws treatment (0=one, 1=both), and extraction (1=no,
2=yes). In analyzing the clinical data (questionnaire study excluded), and measurements Student’s t-
test, paired t-test and Pearson correlation coefficients were used. The statistical significance level
was taken at p≤0.05, in all the tests performed.
33
5. RESULTS
5.1. Subjective pain experience during orthodontic treatment as reported in the
questionnaires
The overall response rate for the questionnaires was 98.6%. Altogether seven questionnaires were
missing, four from the initial archwire placement and three from the activation phase. Throughout
the entire study, five appointments were compromised for two days interval instead of three because
of the adult patients´ working schedules (for these patients only the available data were used and
analyzed). Two patients were excluded, one moved abroad and the other had difficulties in
complying with the study requirements. Thus the number of subjects included in the analyses was
64. There was a financial incentive (50% discount of the total orthodontic treatment costs), for those
who participated in the study. We were able to recruit 66 subjects (two did not complete the study)
out of 68 (that is 97% of the total). Subjects reflect a reasonable representation of our practice.
5.1.1. Prevalence of pain
Prevalence of reported pain during the first three days after different orthodontic procedures for
different stimuli are shown in Table 4. The prevalence was higher after initial archwire insertion
(W1, W2, W3) than after separation of molars (S1, S2, S3) and archwire activation (A1, A2, A3), in
connection with all the stimuli except for sweets at S1 compared to W1. In general, the prevalence
decreased from the first through the second to the third day. The exceptions were for cold
food/drink and fitting posterior teeth together between A1 and A2, for sweets, mastication of food,
and fitting anterior teeth together between W1 and W2, and also for tooth brushing between A2 and
A3. Prevalence of pain was more clearly highest for mastication of food and fitting anterior teeth
together during the second day after the initial archwire, in 93.2% and 89.9%, respectively. Pain
was also very common for fitting the posterior teeth together during W1 and W2, 83% and 81%,
respectively. There were no statistically significant differences except for W1/W3 in cold
food/drink and S1/S3 in tooth brushing (p<0.05= Z value at 1.2-3.8).
The highest frequency of pain was reported after the insertion of initial archwire, in relation to all
items namely, mastication of food in 93.2%, fitting anterior teeth in 82.7%, fitting posterior teeth in
78.6%, tooth brushing in 47.6%, cold in 27.4%, hot in 22.3% and sweets in 9.8% of all subjects.
The differences in the prevalence of the reported pain between the first three corresponding days of
34
different orthodontic procedures (Table 5) related to all other items except for sweets and hot
food/drink at W1/A1, and sweets at S1/W1, were statistically significantly higher at the first day
after initial archwire insertion (W1) compared to both the first days after separation of molars (S1)
and the archwire activation (A1). The prevalence of the experienced pain (Table 5) was quite
similar on the first days after molar separation (S1) and archwire activation (A1) with only two
items, namely, fitting anterior and posterior teeth together showing statistically significant
differences.
Table 4. The prevalences of pain reported by 64 orthodontic patients during the first three days after
each orthodontic procedure, namely, separation of the molars (S1, S2 and S3), initial archwire
placement (W1, W2 and W3), and the first archwire activation (A1, A2 and A3) for different items
of the questionnaire.
Stimulus Days after separation
Days after initial archwire
Days after activation of archwire
S1 %
S2 %
S3 %
W1 %
W2 %
W3 %
A1 %
A2 %
A3 %
Cold food/drink
14.3 11.6 9.5 35.6 28.8 17.9 13.5 16.7 9.8
Hot food/drink
9.5 7.0 2.4 25.4 23.7 17.9 12.1 8.3 6.6
Sweets
9.5 7.0 7.1 8.5 11.9 8.9 6.9 5.0 4.9
Tooth brushing
28.6 20.9 11.9 50.8 49.2 42.9 34.1 20.0 24.6
Mastication of food
50.0 55.8 42.9 88.1 93.2 89.3 56.9 53.3 49.2
Fitting anterior teeth
14.3 14.0 11.9 79.7 89.8 78.6 51.7 43.3 41.0
Fitting posterior teeth
61.9 58.1 45.2 83.1 81.4 71.4 27.6 30.0 24.6
35
Table 5. The statistical significance of the differences in the prevalence of the reported pain
between the first three days of different orthodontic procedures. By Z-test. (P<0.05, Z value 1.2-3.8
and P<0.01, Z value 3.8-5.6 and P<0.001, Z value>5.6).
S1/W1
S2/W2
S3/W3
S1/A1
S2/A2
S3/A3
W1/A1
W2/A2
W3/A3
Cold food/drink
P<0.01 P<0.05 P>0.05 P>0.05 P>0.05 P>0.05 P<0.01 P>0.05 P>0.05
Hot food/drink
P<0.05 P<0.01 P<0.001 P>0.05 P>0.05 P>0.05 P>0.05 P<0.05 P<0.05
Sweets
P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05
Tooth brushing
P<0.01 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.05
Mastication of food
P<0.001 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.001
Fitting anterior teeth
P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001
Fitting posterior teeth
P<0.01 P<0.01 P<0.01 P<0.001 P<0.01 P<0.05 P<0.001 P<0.001 P<0.001
36
5.1.2. The intensity, quality and duration of the reported pain
Based on all pain reports, pain intensity was most frequently reported to be mild (62.5%) followed
by moderate (28.5%) and severe (9%) pain respectively. The distribution of the intensity of the
reported pain symptoms during the first three days after different orthodontic procedures, in relation
to each stimuli included in the questionnaire, is presented in Table 6. During the three days after the
insertion of initial archwire the corresponding distribution of the reported pain intensity was mild
52.7%, moderate 33.9% and severe 13.4%. There were no reports of severe pain during the first
three days after separation of molars and wire activation in connection with cold and hot food/drink,
sweets and tooth brushing. This coincides with the high "no pain" reports related to the
abovementioned items. The highest prevalence of severe pain was found after the initial archwire
insertion, namely on the first day after the procedure mastication of food was reported to cause
severe pain most frequently, by 25.4% of the subjects. Generally reports of the severe pain were
mostly related to the three most frequently reported items: mastication of food, and fitting anterior
and posterior teeth together respectively.
37
Table 6. The distribution of orthodontic patients who experienced pain according to the intensity of
the experienced pain during the first three days after each orthodontic procedure, separation of
molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3).
Days after separation
Days after initial archwire
Days after activation of the archwire
S1 n
S2 n
S3 n
W1 n
W2 n
W3 n %
A1 n %
A2 n %
A3 n % % % % % %
Cold food/drink(n) 11 10 9 35 18 11 10 78.0 22.0
0
10 80.1 19.9
0
6 mild pain moderate pain severe pain
83.2 16.8
0
100 100 61.8 23.9 14.3
70.5 23.6 5.9
90.0 0
10.0
100 0 0
0 0
0 0
Hot food/drink(n) 9 7 5 16 15 11 8 85.8 14.2
0
5 100 0 0
4 mild pain moderate pain severe pain
100 100 100 53.6 40.0 6.7
64.3 35.7
0
100 100 0 0
0 0
0 0
0 0
0 0
Sweets(n) 9 7 8 5 7 5 4 100 0 0
3 100 0 0
3 mild pain moderate pain severe pain
50.0 50.0
0
0 100
66.6 33.4
0
40.0 0
60.0
71.4 0
28.6
60.0 40.0
0
100 0
0 0 Tooth brushing(n) 19 14 8 33 32 27 15
71.4 28.6
0
13 83.5 16.5
0
16 mild pain moderate pain severe pain
83.2 16.8
0
89.0 11.0
0
80.0 20.0
0
70.0 16.7 13.3
58.6 37.9 3.5
70.9 24.9 4.2
86.6 13.4
0 Mastication of food(n) 32 36 28 56 60 57 36
62.8 21.0 16.2
34 74.9 21.9 3.2
31 mild pain moderate pain severe pain
63.9 24.4 11.7
53.1 32.7 14.2
77.6 11.2 11.2
23.0 48.1 28.9
29.0 51.0 20.0
40.0 48.0 12.0
80.0 20.0
0 Fitting anterior teeth(n) 9 8 7 51 57 50 33
63.4 30.0 6.6
28 65.3 30.7 4.0
26 mild pain moderate pain severe pain
49.6 33.6 16.8
83.4 16.6
0
80.0 20.0
0
42.5 44.7 12.8
52.8 32.0 15.2
52.3 34.0 13.7
88.0 12.0
0 Fitting posterior teeth(n) 40 37 29 53 52 46 18
68.8 31.2
0
19 72.3 27.7
0
16
mild pain moderate pain severe pain
61.6 34.6 3.8
68.0 32.0
0
79.0 21.0
0
61.2 28.5 11.3
64.6 28.5 11.3
62.5 27.5 10.0
86.6 15.4
0
The quality of the reported pain as indicated by the pain descriptors during the first three days
after each orthodontic procedure, regarding each item included in the questionnaire is presented
in Table 7. According to the reports sore (65%) was the most frequent descriptor followed by
dull (15.5%), shooting (9.5%) and ache (9.5%). During the three days after the insertion of
initial archwire the corresponding distribution of the pain descriptors were 65.2% for sore,
14.6% for shooting, 12.1% for dull and 8.1% for ache.
Regarding the duration of the reported pain during the first three days after different orthodon-
tic procedures, for different stimuli, in general pain was mostly short lasting in 85% of the
reports (Table 8). During the three days after the insertion of initial archwire the proportion of
38
short and long lasting pain were 75.2% and 24.8% respectively. The differences in the reported
duration of pain (short vs. long), were statistically significant when comparing the three days
after archwire insertion to the corresponding days after archwire activation in all items except
for cold at W2/A2 and sweets at W3/A3.
Wilcoxon Matched-Pairs Signed-Ranks Test was used to study the differences of the intensity,
quality and duration of the reported pain in connection with each item between the first three
days after each orthodontic procedure (Table. 9). No statistically significant difference was
found between S1/S2 in the pain reports of any item. In general most of the significant
differences between the days examined in connection with the intensity, quality and duration of
the reported pain were found between W1/W3 followed by W2/W3 and S1/S3 and S2/S3,
respectively. Differences in the intensity, quality and duration of the reported pain in
connection with cold food/drink were highest and found to be statistically significant between
W1/W3 and W2/W3. Comparison between the differences of the reported pain during the first
three days after archwire activation (A1, A2 and A3) showed statistically significant differences
only with regards to fitting front teeth together. Taking sweets was the only item with no
statistically significant differences of the reported pain between the days tested.
Wilcoxon Matched-Pairs Signed-Ranks Test was also used to study the differences of the
intensity, quality and duration of the reported pain in connection with each item between the
first three days of different orthodontic procedures (Table. 10). Taking sweets was the only
item with no statistically significant differences in the reported pain between the days tested. In
general most of the significant differences were found between W1/A1 followed closely by
S3/W3, W3/A3, S1/W1, S2/W2 and W3/A3, respectively. Comparison between the differences
of the reported pain during the first three days after archwire activation and separation of
molars (S1/A1, S2/A2 and S3/A3) showed statistically significant differences only with regards
to fitting anterior and posterior teeth together.
39
Table 7. The distribution of the quality of experienced pain of 64 orthodontic patients who
experienced pain during the first three days after each orthodontic procedure, separation of molars
(S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3).
Days after separation
Days after initial archwire
Days after activation of the archwire
S1 n %
S2 n %
S3 n %
W1 n %
W2 n %
W3 n %
A1 n %
A2 n %
A3 n %
Cold food/drink (n) sore shooting dull ache
9 49.6 32.5 17.9
0
7 60.0 40.0
0 0
6 25.0 50.0 25.0
0
23 42.8 42.8 4.8 9.6
18 41.2 41.2 11.7 5.9
11 39.7 30.2 20.1 10.0
10 22.0 44.5 33.5
0
11 19.9 50.0 19.9 10.2
6 16.3 50.0 33.7
0 Hot food/drink (n) sore shooting dull ache
6 74.7
0 25.3
0
4 100 0 0 0
2 100
0 0 0
16 53.3 20.0 20.0 6.7
15 50.0 28.6 21.4
0
11 59.8 20.1 10.1 10.0
8 28.3 28.3 43.4
0
5 20.5 39.7 39.7
0
4 24.6 50.8 24.6
0 Sweets (n) sore shooting dull ache
6 74.7 25.3
0 0
4 67.1 32.9
0 0
4 66.6 33.4
0 0
5 80.0 20.0
0 0
8 85.7 14.3
0 0
5 79.8 20.2
0 0
4 100 0 0 0
3 100 0 0 0
3 100 0 0 0
Tooth brushing (n) sore shooting dull ache
18 83.2 8.4 8.4 0
13 89.0
0 11.0
0
8 79.8
0 20.2
0
33 80.0
0 10.0 10.0
31 82.7 10.4 6.9 0
27 79.2 16.6 4.2 0
15 57.3 7.1
14.1 21.5
13 66.5
0 25.0 8.5
16 67.0 6.5
20.0 6.5
Mastication of food (n) sore shooting dull ache
32 45.9 14.2 19.0 20.9
36 49.9 12.5 29.2 8.4
24 66.6 5.6
16.5 11.3
56 59.6 5.8
13.5 21.1
60 69.0 3.6
14.6 12.8
57 72.0 7.9
14.0 6.1
36 72.8 3.0
15.1 9.1
34 65.5 3.2
21.9 9.4
31 76.6
0 16.6 6.8
Fitting anterior teeth (n) sore shooting dull ache
9 49.6
0 33.6 16.8
9 66.8
0 16.6 16.6
9 33.6 16.8 49.6
0
51 57.4 6.4
17.0 19.2
58 60.3 7.6
15.1 17.0
50 77.2 4.6
11.3 6.9
33 50.0 10.0 16.6 23.4
28 65.3 7.6
15.5 11.6
26 68.0 3.9
20.0 8.1
Fitting posterior teeth (n) sore shooting dull ache
40 57.7 7.7
15.3 19.3
37 59.9 8.1
19.9 12.1
29 57.8 5.3
31.5 5.4
53 59.2
0 28.5 12.3
52 70.8 2.1
16.7 10.4
46 70.0 5.0
15.0 10.0
27 81.5
0 12.3 6.2
19 94.3
0 5.7 0
16 80.1
0 13.4 6.5
40
Table 8. The distribution of the duration of experienced pain of 64 orthodontic patients who
experienced pain during the first three days after each orthodontic procedure, separation of
molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and
A3).
Days after separation
Days after initial archwire
Days after activation of the archwire
S1 n %
S2 n %
S3 n %
W1 n %
W2 n %
W3 n %
A1 n %
A2 n %
A3 n %
Cold food/drink (n) short long
9
66.5 33.5
7
80.2 19.8
6
100 0
23
76.1 23.9
18
88.2 11.8
11
89.9 10.1
10 100 0
11
89.8 10.2
6
100 0
Hot food/drink (n) short long
6 74.7 25.3
4 100 0
2 100 0
16 79.9 20.1
15 92.8 7.2
11 89.9 10.1
8 100 0
5 100 0
4 100 0
Sweets (n) short long
6 74.7 25.3
4 100 0
4 100 0
5 40.0 60.0
8 71.4 28.6
6 100 0
4 100 0
3 100 0
3 100 0
Tooth brushing (n) short long
18 100 0
13 100 0
8 100 0
33 76.6 23.4
31 86.2 15.8
27 91.6 8.4
15 85.9 14.1
13 91.5 8.5
16 100 0
Mastication of food (n) short long
32 81.0 19.0
36 83.3 16.7
27 94.4 5.6
57 53.8 46.2
60 65.6 34.4
57 82.0 18.0
36 94.0 6.0
34 96.8 3.2
31 96.7 3.3
Fitting anterior teeth (n) short long
9 66.4 33.6
9 83.4 16.6
9 100 0
51 68.0 32.0
57 79.3 20.7
50 86.4 13.6
33 86.6 13.4
28 96.1 3.9
26 100 0
Fitting posterior teeth (n) short long
30 73.0 27.0
37 84.0 16.0
29 94.7 5.3
53 79.6 20.4
52 87.5 12.5
46 85.0 15.0
18 93.8 6.2
19 100 0
16 100 0
41
Table 9. The statistical significance of the differences in the intensity, quality and duration of
the reported pain during the first three days after each orthodontic procedure, separation of
molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and
A3). By Wilcoxon Matched-pairs Signed-Ranks Test.
S1/S2 S1/S3 S2/S3 W1/W2 W1/W3 W2/W3 A1/A2 A1/A3 A2/A3
Cold food/drink
Intensity .41 .18 .56 .06 .003 .029 .70 .06 .06
Quality .50 .58 1.0 .18 .032 .48 .46 .19 .10
Duration .52 .15 .41 .07 .005 .032 .41 .08 .06
Hot food/drink
Intensity .32 .18 .32 .61 .025 .012 .18 .16 .56
Quality .32 .16 .32 .56 .37 .75 .18 .17 .41
Duration .16 .16 .32 .78 .16 .10 .16 .18 .56
Sweets
Intensity .16 .59 .58 1.0 .16 .10 .32 .56 1.0
Quality .08 .74 1.0 .16 1.0 .16 .32 .56 1.0
Duration .18 .48 1.0 .65 .18 .10 .32 .56 1.0
Tooth brushing
Intensity .16 .019 .08 .83 .11 .09 .16 .36 .41
Quality .16 .019 .08 .000 .10 .036 .13 .35 .32
Duration .18 .014 .08 .28 .033 .16 .28 .36 .70
Mastication of food
Intensity .44 .18 .014 .65 .07 .023 .47 .11 .85
Quality .86 .038 .011 .006 .040 .31 .85 .12 .12
Duration .74 .09 .011 .54 .016 .002 .25 .052 .26
Fitting anterior teeth
Intensity .27 .75 .35 .60 .07 .36 .08 .005 .050
Quality .71 1.0 .68 .09 .012 .71 .021 .015 .87
Duration .71 .46 .71 .81 .08 .040 .041 .023 .46
Fitting posterior teeth
Intensity .11 .002 .027 .46 .48 .16 .64 .18 .22
Quality .21 .09 .08 .000 .013 .08 .65 .77 .79
Duration .07 .005 .033 .32 .06 .27 .77 .38 .38
42
Table 10. The statistical significance of the differences in the intensity, quality and duration of
the reported pain during the first three days after each orthodontic procedure, separation of
molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and
A3). By Wilcoxon Matched-pairs Signed-Ranks Test.
S1/W1 S2/W2 S3/W3 W1/A1 W2/A2 W3/A3 S1/A1 S2/A2 S3/A3
Cold food/drink
Intensity .006 .027 .41 .009 .09 .09 .80 .56 .56
Quality .034 .18 .59 .054 .64 .20 .72 .28 .41
Duration .028 .11 .31 .003 .09 .09 .55 1.0 .56
Hot food/drink
Intensity .021 .005 .034 .015 .005 .034 1.0 .65 1.0
Quality .22 .13 .033 .16 .16 .09 1.0 1.0 1.0
Duration .058 .005 .035 .025 .007 .035 .48 .65 1.0
Sweets
Intensity .70 .68 .70 .46 .20 .41 .33 .21 .48
Quality .56 .70 .70 .70 1.0 .41 .48 .48 .48
Duration .70 .65 .56 .46 .21 .56 .48 .65 .65
Tooth brushing
Intensity .003 .000 .000 .000 .000 .017 .87 1.0 .09
Quality .002 .67 .002 .10 .59 .39 .25 .55 .08
Duration .001 .000 .000 .000 .000 .034 .76 1.0 .10
Mastication of food
Intensity .000 .000 .000 .000 .000 .000 .28 .24 .08
Quality .09 .83 .001 .001 .21 .003 .67 .41 .89
Duration .000 .000 .000 .000 .000 .000 .82 .20 .82
Fitting anterior teeth
Intensity .000 .000 .000 .000 .000 .000 .019 .012 .012
Quality .000 .000 .000 .008 .051 .015 .003 .010 .06
Duration .000 .000 .000 .000 .000 .000 .013 .026 .012
Fitting posterior teeth
Intensity .11 .050 .001 .000 .000 .000 .014 .036 .13
Quality .21 .57 .042 .000 .002 .001 .004 .004 .12
Duration .27 .08 .011 .000 .000 .000 .007 .022 .19
43
The intensity in relation to different pain descriptors and duration of the reported pain is shown in Figure 8. Results are based on the combination of the scores, from the seven items throughout three days of the three stages of the treatment (Total Pain Index, TPI, page 26 ), thus describing the pain experienced during the study period.
0
1
2
3
sore shooting dull acheQuality of pain
ain
f p
y o short
sit
long en
Int
Figure 8. The relationship between the intensity, quality and duration of the pain reports given by the subjects (Total Pain Index, score = 0-1512, page 26) during orthodontic treatment. The intensity values are based on (0=no pain, 1=mild pain, 2=moderate pain, 3=severe pain). 5.1.3. Pain experienced during the three days subsequent to each orthodontic procedures The pain scores (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) for each of the first three days after different stages of the orthodontic treatment are shown in Fig. 9. The pain scores after each different treatment stages decreased during the first three days: after separation of molars from 13.6 for S1, to 10.6 for S2 and further to 7.9 for S3. After initial archwire insertion the pain
44
scores were 28.6 for W1, 23.5 for W2 and 16.8 for W3. The pain scores after the activation of archwire were 12.6 for A1, 9.6 for A2 and 7.9 for A3, respectively. Reduction of reported pain symptoms from the first day to the third was evident at all the stages, suggesting that the first day is the most painful. Additionally, the initial archwire insertion was by far the most painful stage of the treatment. The differences in the pain scores were statistically significant (z-test) for the combined three days, between separation of the first molars and initial archwire insertion and between initial archwire insertion and its activation, the difference between the separation of molars and the archwire activation stage was not statistically significant. The differences in the pain scores were statistically significant within each treatment stage between; S1 and S2 (p=.040), S1 and S3 (p=.008), W1 and W3 (p=.000), W2 and W3 (p=.005), A1 and A3 (p=.008) and among different days in different stages of treatment as follows: S1 and W1 (p=.002), S2 and W2 (p=.000), S3 and W3 (p=.001), W1 and A1 (p=.000), W2 and A2 (p=.000), W3 and A3 (p=.005). 0
5
10
15
20
25
30
S1 S2 S3 W1 W2 W3 A1 A2 A3
fitting back teethfitting front teethmasticationtooth brushingsweethotcold
Figure 9. Total index values (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) of the perceived pain for seven items for each of the three days after separation of the molars (S1, S2, S3), after initial archwire insertion (W1, W2, W3) and after wire activation (A1, A2, A3).
45
5.1.4. Pain experienced in relation to different stimuli of the questionnaire The pain scores for each of the seven stimuli combined for different stages of orthodontic treatment (Total Pain Index for one Stimuli, TPIS, score=0-216, page 26) are presented in Figure 10. Sweets gave the lowest score 1.7, followed by hot food/drink 6.2, cold food/drink 10.0 and tooth brushing 10.4. The highest pain scores were found in response to mastication of food and fitting front or back teeth together, 33.8, 27.0 and 24.6, respectively.
separationinitial archwire1st activation
co
ld hotsw
eet
tooth bru
shing
mastica
tion
fitting fr
ont teeth
fitting bac
k teeth
Figure 10. The reported pain for each of the seven items combined for different stages of treatment (Total Pain Index for one Stimuli, TPIS, score=0-216, page 26).
46
10
0
20
30
40
50
5.1.5. The relationship between subjective pain reports and the analgesic consumption The proportion of subjects taking analgesics during the first three days after different stages of treatment is presented in Figure 11. Overall analgesic consumption in the sample was limited to two patients in the separation stage and archwire activation stages and to 15 patients after the initial archwire placement. More analgesics were consumed on the second day after both the separation of molars and the initial archwire than on the first day. During the W3 the use of the analgesics dropped, and none was needed during S3 and A3.
0
5
10
15
20
Separation Initialarchwire
Firstactivation
%
1st day2nd day3rd day
Figure 11. Percentage of the patients (n=64) taking analgesics during the first days after separation of the molars, after initial archwire insertion and archwire activation.
47
Proportion of subjects taking analgesics and that of subjects reporting any pain during each studied day after different stages of orthodontic treatment are shown in Figure 12. Patients responding to any of the items were included, therefore the results from the questionnaire reflects either if there was discomfort associated with different orthodontic procedures or not (yes or no). A correlation (r=0.35) between these two variables was low although statistically significant (p=.006).
0
20
40
60
80
100
S 1st S 2nd S 3rd W 1st W2nd
W 3rd A 1st A 2nd A 3rd
Analgesic cosumptionPain reports
%
.
Figure 12.The proportion (%) of subjects reporting pain and using analgesics during the first three days after separation of molars (S), initial archwire insertion (W) and wire activation (A), (n=64). Patients who had taken medication, reported higher pain scores in connection with all items of the questionnaire except for sweets when compared to those without medication, these differences were statistically significant (t-test) only in fitting front (p=.006) and back (p=.026) teeth together.
48
5.1.6. Relationship between subjective pain reports and age, gender, ext-raction(s) and extent of treatment The difference between the Total Pain Index, TPI, maximum score=1512, of the patients under and above 16 year of age was not statistically significant. However, the older group reported symptoms more frequently and pain was of higher intensity and longer duration in response to mastication on the second day after archwire activation (p=0.047) and initial archwire insertion (p=0.028), respectively. Gender and tooth extractions did not have significant effects on the pain reports. With the treatment of both jaws more discomfort was reported in fitting front and back teeth together, however, the total pain scores between patients with both jaws treated and only one jaw treated did not differ significantly. 5.2. Clinical study 5.2.1. Responses to cold stimulation Proportion of responding teeth to cold stimulation at 15ºC and 0ºC at different stages of the treatment is presented in Table 11. In some of the patients molars were bonded and not separated for the banding procedure. The later measurements from the banded molars were discontinued. A higher proportion of the teeth responded at 0ºC when compared to 15ºC, at all stages of the treatment in all tooth groups examined. Statistically significant differences (Z-test) were found between the proportion of responding teeth in 15ºC and 0ºC at different stages of treatment, namely; incisors and all teeth combined during all the different stages of treatment, premolars and canines during the initial (TI) and three days after the first archwire (TF).
49
Table 11. Proportion of responding teeth to cold stimulation at 15 and 0ºC at different stages of orthodontic treatment. Stages of orthodontic treatment
15ºC % n
0ºC % n
Initial (before treatment) incisors premolars and canines molars all teeth
10.4 33 4.8 21 1.3 2 6.2 56
38.7 122 24.2 104 20.0 30 28.6 256
After separation (S3) molars
3.9 4
22.5 23
Archwire activation (W3) incisors premolars and canines molars all teeth
16.3 45 9.6 36 8.1 11 11.7 92
47.7 132 27.5 103 27.8 37 34.6 272
Before activation incisors premolars and canines molars all teeth
13.3 37 3.5 13 3.1 4 6.9 54
41.2 113 24.3 89 27.6 35 30.9 237
After activation (A3) incisors premolars and canines molars all teeth
17.3 49 6.1 23 2.3 3 9.5 75
38.4 109 23.6 90 19.5 25 28.2 224
In order to study the overall dental cold sensitivity at different stages of orthodontic treatment the
results from maxillary and mandibular teeth were combined and grouped in three; 1) incisors, 2)
canines and premolars, and 3) molars. The mean VAS values in response to cold stimulation at
15ºC for each tooth group at different stages of treatment are shown in Figure 13. The VAS ratings
(SE) at the initial stage were 0.3 (0.3) in molars, 0.65 (0.2) in premolars and canines, 2.1 (0.6) in in-
cisors. The VAS ratings were higher at three days after initial archwire insertion. The mean values
(SE) were 4.0 (0.9) for incisors, 1.9 (0.5) for premolars and canines and 2.2 (1.0) for molars.
50
0
2
4
6
8
10
12
14mm
molars
premolars and caninesincisors
Fig. 13
I II III IV V
Figure 13. The mean VAS pain ratings to cold stimulation at 15ºC in different tooth groups at
different stages of the treatment (I = initial, II = separation of molars, III = three days after
initial archwire insertion, IV = before wire activation and V = three days after activation).
Maxillary and mandibular teeth were combined in each tooth group.
Figure 13. The mean VAS pain ratings to cold stimulation at 15ºC in different tooth groups at
different stages of the treatment (I = initial, II = separation of molars, III = three days after
initial archwire insertion, IV = before wire activation and V = three days after activation).
Maxillary and mandibular teeth were combined in each tooth group.
The mean VAS values in response to cold stimulation at 0ºC for each tooth group at different
stages of treatment are shown in Figure 14. The highest VAS ratings were recorded in the
initial archwire insertion stage. The incisors demonstrating increased sensitivity throughout the
study period, 10.7 (1.5) at the initial stage, 14.2 (1.8) at three days after initial archwire
insertion, 13.8 (2.2) at activation and 12.7 (2.1) at three days after activation stage. The
mean,(SE) in the molars increased from the initial 4.45 (1.2) to 9.3 (1.9) three days after initial
archwire activation. Smaller changes were observed in the premolars and canines group during
this study.
The mean VAS values in response to cold stimulation at 0ºC for each tooth group at different
stages of treatment are shown in Figure 14. The highest VAS ratings were recorded in the
initial archwire insertion stage. The incisors demonstrating increased sensitivity throughout the
study period, 10.7 (1.5) at the initial stage, 14.2 (1.8) at three days after initial archwire
insertion, 13.8 (2.2) at activation and 12.7 (2.1) at three days after activation stage. The
mean,(SE) in the molars increased from the initial 4.45 (1.2) to 9.3 (1.9) three days after initial
archwire activation. Smaller changes were observed in the premolars and canines group during
this study.
51
0
2
4
6
8
10
12
14mm
molars premolars and canine
incisors
Fig . 14 I II III IV V
Figure 14. The mean VAS pain ratings to cold stimulation at 0ºC in different tooth groups at
different stages of the treatment (I = initial, II = separation of molars, III = three days after
initial archwire insertion, IV = wire activation and V = three days after activation). Maxillary
and mandibular teeth were combined in each tooth group.
Figure 14. The mean VAS pain ratings to cold stimulation at 0ºC in different tooth groups at
different stages of the treatment (I = initial, II = separation of molars, III = three days after
initial archwire insertion, IV = wire activation and V = three days after activation). Maxillary
and mandibular teeth were combined in each tooth group.
5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0ºC and 5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0ºC and
15ºC. 15ºC.
The correlation between the VAS ratings to cold stimulation at 0 and 15ºC at different stages of
treatment is presented in Table 12. Using paired t-test for the statistical analysis revealed that
except for molars at the initial stage (p=.131) and three days after activation (p=.083), all other
tooth groups at all the stages were at a statistically significant level.
The correlation between the VAS ratings to cold stimulation at 0 and 15ºC at different stages of
treatment is presented in Table 12. Using paired t-test for the statistical analysis revealed that
except for molars at the initial stage (p=.131) and three days after activation (p=.083), all other
tooth groups at all the stages were at a statistically significant level.
52
Table 12. Correlations (Pearson correlation coefficient) between the VAS values in response of
different groups of permanent teeth to cold at 0 and 15ºC at different stages of orthodontic
treatment.
Treatment phase Molars r
(p)
Premolars and canines
r (p)
Incisors r
(p)
Before treatment After separation of the first molars On the 3rd day after initial arch-wire insertion Before the activation of the archwire On the 3rd day after activation
0.20
(.131)
0.32 (.044) *
0.51
(.000) *
0.30 (.033) *
0.25
(.083)
0.50
(.000) *
0.69 (.000) *
0.54
(.000) *
0.70 (.000) *
0.63
(.000) *
0.40 (.002) *
0.64
(.000) *
0.77 (.000) *
The mean electrical thresholds of each tooth group with the maxillary and mandibular teeth
combined at different stages of the treatment are shown in Figure 15. The mean thresholds (SE) we-
re; 28.2 (2.2), 25.3 (2.3), 24.7 (2.2) and 25.5 (3.2) in molars, 19.3 (1.2), 17.2 (2.0), 17.8 (1.4), 17.1
(1.2), in premolars and canines and 13.2 (0.9), 12.0 (0.9), 12.1 (1.0), 12.7 (1.1) in the incisors, res-
pectively. The difference between the means was statistically significant (p=.031) in incisors
between the archwire activation and three days after wire activation.
53
0
5
10
15
20
25
30
35 µA
F ig. 15
molars
premolars and canines
incisors
I II III IV V
Figure 15. The mean dental electrical thresholds in different tooth groups at different stages of
the treatment (I = initial, II = three days after the separation of molars, III = three days after the
initial archwire insertion, IV = before wire activation and V = three days after activation).
Maxillary and mandibular teeth were combined in each tooth group.
Figure 15. The mean dental electrical thresholds in different tooth groups at different stages of
the treatment (I = initial, II = three days after the separation of molars, III = three days after the
initial archwire insertion, IV = before wire activation and V = three days after activation).
Maxillary and mandibular teeth were combined in each tooth group.
5.3. Comparison of two different orthodontic mechanotherapies 5.3. Comparison of two different orthodontic mechanotherapies
In general the differences in the prevalence of the pain between the two fixed appliances were
small and statistically significant only in connection with some of the questionnaire items
which altogether gave the most frequent pain reports. Such items were mastication, fitting
anterior and posterior teeth together.
In general the differences in the prevalence of the pain between the two fixed appliances were
small and statistically significant only in connection with some of the questionnaire items
which altogether gave the most frequent pain reports. Such items were mastication, fitting
anterior and posterior teeth together.
Differences in the pain scores between different fixed appliances, during the initial archwire
insertion and wire activation stage, in response to each item (Pain Index of one stimuli in two
Stages, page 26) is presented in Table 13. No statistical significant difference was found.
Mastication of food was reported to have the highest score in both fixed appliances in the
combined initial archwire and wire activation stage. Followed by fitting anterior and posterior
teeth together, respectively.
Differences in the pain scores between different fixed appliances, during the initial archwire
insertion and wire activation stage, in response to each item (Pain Index of one stimuli in two
Stages, page 26) is presented in Table 13. No statistical significant difference was found.
Mastication of food was reported to have the highest score in both fixed appliances in the
combined initial archwire and wire activation stage. Followed by fitting anterior and posterior
teeth together, respectively.
54
Table 13. The reported pain scores during the initial archwire and wire activation stage (Pain
Index of one stimuli in two Stages, page 26) for each of the items in different fixed appliances.
Alexander technique Viazis technique p* mean SD mean SD Cold 9.8 14.5 11.9 19.6 .668 Hot 5.5 10.1 8.5 19.7 .507 Sweet 1.5 6.4 0.5 1.3 .486 Tooth brushing 9.4 17.8 12.8 19.8 .521 Mastication 25.9 27.0 31.5 27.5 .474 Fitting anterior teeth 24.3 27.7 30.0 31.4 .508 Fitting posterior teeth 15.8 21.7 20.9 19.1 .386
* by t-test
The reported pain scores from each of the days after the initial archwire (W1, W2, W3) and the
wire activation (A1, A2, A3) were compared and no statistical differences were found in
different fixed appliances. After the initial archwire insertion pain reports were more frequent,
having higher score, in the Viazis technique than the Alexander. However, after the wire
activation stage the pain scores were higher in the Alexander technique.
The changes in the reported pain scores (Index 1, score=0-24) from the first three days after
initial archwire to the corresponding days after wire activation of each item in different fixed
appliances were studied and analyzed further. Difference of the pain reports was calculated by
subtracting the pain scores at the initial archwire insertion from the reported pain scores during
the wire activation. Generally the pain scores from the initial archwire to the wire activation
have reduced more in the Viazis technique, being at a statistically significant level only on the
first days during mastication. There was a reduction of pain scores from the initial archwire
insertion to the archwire activation in response to all items but on the first days in sweets with
Viazis technique also on the second and third days in tooth brushing with Alexander technique.
55
5.3.1. Dental cold sensitivity and electrical thresholds in two different
orthodontic mechanotherapies.
The mean VAS ratings to cold at 15ºC at different stages of treatment in connection with the
two different fixed orthodontic appliances were studied and analyzed further. Already at the
initial stage, before treatment, there was a statistically significant difference between the two
system in premolars and canines (p=.014) and all teeth combined (p=.032). There was a statisti-
cal significant differences in the corresponding values also three days after initial archwire
insertion (p=.013, p=.008) and at the activation of the archwire (p=.039, p=013) respectively.
The mean VAS ratings in response to cold stimulation at 0ºC at different stages of treatment in
reaction to the two different fixed orthodontic appliances were studied and analyzed further. No
statistically significant differences were found between the two systems at the initial stage. The
mean VAS values in the other stages of the treatment (three days after initial archwire, before
activation of archwire and three days after activation) were lower in the Viazis technique
compared to the Alexander. With all the teeth combined the differences were statistically sig-
nificant three days after initial archwire (p=.012), at activation (p=.017) and three days after
activation (p=.003). The differences in the mean VAS ratings were also statistically significant
in premolars and canines three days after initial archwire placement and three days after wire
activation (p=.024, p=.001) respectively and in molars (p=.035) three days after archwire
activation.
The mean dental electrical thresholds related to the two different fixed orthodontic appliances
were studied and analyzed further. There were no statistically significant differences at the
initial stage between the two groups. However, at the activation stage all tooth groups were less
sensitive in the Viazis technique with the difference in the incisors (p=.034), premolars and ca-
nines (p=.005) and all teeth combined (p=.000) being at a statistically significant level. Also a
significant difference was found three days after archwire activation, when the teeth were
combined (p=.020). This might as well point to, increased pulpal disturbances.
56
5.3.2. Tooth movements in two different orthodontic mechanotherapies
The results from tooth movements with different fixed appliances, using the irregularity index,
defined as the summed displacement of adjacent anatomic contact points (Little 1975) for the
anterior (canine to canine) crowding showed no statistically significant difference between the
two techniques, either before or after three months of fixed orthodontic treatment. The mean
crowding values for each patient was used for statistical analysis. In extraction cases, patients
treated with the Viazis technique demonstrated the mean space closure at the third month to be
2.8mm compared to less than 1mm using Alexander technique.
57
6. DISCUSSION
6.1. Study subjects
The sample was formed by consecutive cases from patients who were willing to participate. As seen
in many practices of contemporary orthodontics (Gottlieb and Voges, 1984) the number of adult pa-
tients seeking therapy is increasing. This explains the high mean age of 26.4 years of the study sam-
ple. Because age distribution was rather wide age was included in the statistical analyses as a
confounding factor. Gender distribution was not even in the sample, female subjects were over
presented, as is the case in most orthodontic practices. The effect of gender was also controlled
during the statistical analyses, and proved not to have an effect on the results.
Size of the study sample was adequate for this study design. Because of the small number of
participants, the six patients who were treated with standard edgewise technique were not included
in the statistical analysis as a separate group. When comparing the two different fixed orthodontic
appliances there was no difference between the two study groups as regard to the age and gender.
6.2. Measurement of the experienced pain
6.2.1. The questionnaire
Most of the existing literature on the pain and discomfort related to orthodontic treatment has con-
centrated on the intensity of pain with different evaluating methods, i.e. the Verbal Rating Scale or
the Visual Analogue Scale.
In the present study subjective pain symptoms subsequent to different stages of orthodontic
treatment were recorded using the questionnaire structured to include the intensity, quality and the
duration of the experienced pain. Attempts were made to structure the questionnaire as simple as
possible to minimize the difficulties usually involved with filling out questionnaires especially
regarding the youngest study subjects. To avoid a large volume of questionnaires and patients con-
fusion, considering the longitudinal nature of this study, it was decided to combine the intensity,
quality and duration of the pain symptoms in one questionnaire. The same form was filled out by
the patients during three consecutive days after each orthodontic procedures, namely after
separation of first molars, insertion of the initial archwire and after the first archwire activation.
58
Cooperation from the patients during the study was excellent, especially considering the time and
effort required for the completion of the repeated clinical tests and questionnaires during different
stages of treatment.
Orthodontic tooth movement is believed to cause varying pain and discomfort to patients (SBU
2005). The first day after each orthodontic procedure has been suggested as being associated with
the most discomfort experienced (Tayer and Burek 1981, Brown and Moerenhout 1991, Jones and
Chan 1992, Scheurer et al. 1996, Yozgatian et al. 2008). The time envelope for this perception has
also been reported to peak on the first and second days and to decrease to minor levels after five
days (Jones 1984, Jones and Richmond 1985, Sinclair et al. 1986, Feinmann et al. 1987, Kvam et al.
1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jones and Chan 1992, Scheurer 1996). Further-
more, Soltis et al. (1971) found that patient’s proprioceptive and discriminatory ability was reduced
four days after the insertion of orthodontic appliances. The patient’s discomfort at onset and during
various stages of treatment was attributed to the lowering of the pain threshold and disruption of the
level of proprioception of the nerve endings in the periodontal ligament (Jones 1984). It seemed
appropriate and was decided to follow the pain experience for three days after each orthodontic
procedure. In this sample, the first day after each procedure was reported to be related to most
discomfort, with systematic relief of the pain experience from the first to the third day.
Questions regarding the occurrence of pain as response to seven different stimuli were included
(Appendix I). The selection of these stimuli is a critical task, since most often and justifiably so; the
variables are chosen to reflect the effects of orthodontic forces on periodontal tissues, such as
mastication of food, fitting anterior and posterior teeth together. Included were also functions that
would provide information to study the possible effects of the orthodontic forces on the dental pulp,
such as the responses to cold and hot food/drink. Eating sweets was included to serve as the control
as well as an indicator of possible responses from exposed dentine. Therefore comparing these
selected stimuli seemed logical because there is a difference in the induction of pain responses for
example from, taking sweets, cold food/drink and mastication of food, which can be related to
exposed dentin, pulpal and/or periodontal inflammation and hypersensitivity. The most frequent
variables describing pain experience related to orthodontic treatment were mastication of food,
fitting anterior and posterior teeth together followed by tooth brushing, cold and hot food or drink,
respectively. Eating sweets only seldom induced any pain or discomfort.
Responses from the TMJ and soft tissues (lips, cheeks, gingiva and tongue) to orthodontic ap-
pliances were not included in the questionnaire. Patients were directed to possibly respond to the
59
sensations evoked by orthodontic appliances to the teeth only. Scheurer et al. (1996) have also
reported that TMJ and soft tissues were not significantly affected by fixed orthodontic appliances,
but the discomfort during orthodontic therapy was mainly localized at the teeth.
There were no questionnaires given to the patients before the treatment, although it could be
hypothesized that the discomfort during the orthodontic treatment may be associated with the
preexisting pathologies and malocclusions. This should be taken into account when considering the
pain symptoms and discomfort which orthodontic treatment may induce. However, during the
process of data collection for diagnostic purposes none of the patients included in the study
indicated to have suffered from any dental pain. Moreover, responses to the questionnaire showed
considerable differences in the pain reports among different stages of treatment.
The method used for assessment of the intensity of pain in this study was a numeric rating scale and
adopted version of the verbal rating scale (Bond 1979). It has been successfully used in previous
studies (Newman 1980, Jones 1984, Kontturi-Närhi 1993). The method proved to be reliable, and
was considered adequate for the purpose of this study, although, it may pay more attention to the
emotional, cognitive and motivational variables that modify the pain or discomfort sensation (Jones
1984).
Estimating quality of the experienced dental pain has been excluded from the pain research in
orthodontics. Evaluating quality of pain symptoms, reflecting also the intensity of pain in
hypersensitive dentin proved to be a reliable method and gave valuable information in a study by
Kontturi-Närhi (1993). Consequently, for the first time in orthodontic literature the present study
included systematic evaluation of the quality of pain symptoms induced by different orthodontic
procedures.
The descriptors of the type or quality and duration of pain have been used earlier (Addy et al.
1987b, Orchardson and Collins 1987a, Kontturi-Närhi 1993). McGill’s Pain Questionnaire MPQ, or
verbal checklist were not used in the present study because of the restrictions due to the length and
the laboriousness of the questionnaire, although this method has advantages like it’s
multidimensional nature and better ability to express the affective aspects of pain (Gracely et al.
1978, Duncan et al. 1989). Even in the MPQ the vocabulary is limited and moreover, it’s use is
time-consuming (Gracely et al. 1978). According to Curro (1990) no pain-word questionnaire has
sufficient properties for an ideal pain measurement.
60
In the studies of pain connected to orthodontic treatment, duration of the pain experience is most
often referred to and usually measured either in hours or days. In addition to the measurement of the
time envelop of the pain related to orthodontic treatment for three consecutive days, it was found in
this study necessary to also evaluate and assess the duration of such immediate pain symptoms as
they occur. Therefore, patients were requested to respond to the duration (short or long) of the
provoked painful sensation. Although, rather crude, it was chosen to keep the questionnaire simple.
A quite similar binary scale for the description of pain duration has been used satisfactorily
(Kontturi- Närhi 1993).
The need to have numerical values for the statistical analyses lead to study a possible relationship
between the intensity, quality and the duration of the experienced pain. Further assessment of the
results revealed the existence of a relationship between the intensity of the different descriptors used
to explain the quality of pain symptoms. The intensity increased from sore to shooting and further
to dull pain, with ache having the highest intensity. Looking at the association between the intensity
and the quality of the pain experienced one might argue that the differences between the intensity of
the pain descriptors were small and not statistically significant. However, the pain descriptor
changes at different stages of treatment (separation of the first molars, initial archwire insertion and
archwire activation) did not exceed 6.5%, with the average changes being at less than 2% level.
Therefore, it could not have affected the results significantly. Long duration pain had reportedly
higher intensity than short lasting pain. Based on the association between the intensity, quality and
duration of pain symptoms an Index (page 26) was formed describing the pain experience. It was
justified to arrange the descriptors of pain in such a way so that the combination of the intensity,
quality and the duration of pain reports would facilitate the use of statistical methods. The
sensitivity and reliability of the Pain Index was confirmed when the results from the prevalence,
intensity, quality and the duration of the pain reports were considered separately. Evaluation of the
results as regards to the Pain Index, therefore, should be handled with caution, since they do not
represent absolute values, rather a combined measure of the intensity, quality and duration of the
pain experienced
6.2.2. Subjective pain symptoms related to different orthodontic procedures
Prevalence of the pain was highest after the placement of the initial archwire in comparison to the
separation of molars and activation of the archwire. Proportion of patients who experienced pain
was 70% after separation of molars, 96% after initial archwire insertion and 69% after archwire
activation. These results are in agreement with the previous investigations, Kvam et al. (1987) re-
61
ported that 95% of all patients experienced from fixed orthodontic appliances (initial archwire),
Scheurer et al. (1996) also reported the prevalence of pain to be at 94% within the first 24 hours.
Similar observations have been made (Wilson et al. 1989, Ngan et al. 1989 and 1994, Jones and
Chan 1992). The pain experienced after each of the three orthodontic procedures had higher pain
score in the first day, which gradually decreased toward the third day. A point worth mentioning
here is that over all, during the initial archwire insertion higher proportion of the subjects had pain -
on the second day than on the first day. However, when considering the intensity, quality and the
duration of pain, the total score for the pain experienced was higher during the first day.
Prevalence of pain experience during the first days after each orthodontic procedure also indicates,
statistically significant differences between the first day after the initial archwire insertion (W1) and
the first days after separation of molars (S1) in connection with all items but sweets, also between
(W1) and the fist day after the archwire activation (A1) except for sweets and hot food/drink.
However, such statistical differences were limited only to fitting teeth together between the
archwire activation (A1) and separation of molars (S1).
6.2.3. Intensity, quality and duration of the pain symptoms
The intensity of the reported pain during the study period (all three stages combined) was most
frequently mild 62.5%, followed by moderate 28.5% and severe pain 9%. However, after the
insertion of initial archwire, which was reported to be the most painful stage of the treatment, the
pain reports showed higher intensities, 52.7% being mild, 33.9% moderate and 13.4% severe pain.
Pain intensity in the present study cannot be compared directly to the study by Jones (1984).
However, in contrast to his conclusions that out of 30 patients, 23 suffered moderate to severe
discomfort, in the present study mild pain showed by far the highest proportion among the reports.
According to Locker and Grushka (1987), most of the orofacial pain symptoms were reported as
mild and that severe or intolerable orofacial pain was found in 11.5% of their subjects. Gradual de-
crease of the reported intensity of pain from the first to third day was apparent in the present study -
which is in agreement with the previous reports (Jones 1984, Jones and Richmond 1985, Sinclair et
al. 1986, Feinmann et al. 1987, Kvam et al. 1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jones
and Chan 1992, Scheurer 1996). The results of the present study indicate that the pain experienced
during the initial archwire insertion was the most intense. Also the first day after each orthodontic
treatment stage was connected with the highest discomfort, which was generally of mild to
moderate intensity.
62
The proportions of different types or qualities of the pain symptoms reported during the study
period were 63.5% for sore, 14.3% for shooting, 14.3% for dull and 7.9% for aching pain. The first
day after any of the three orthodontic treatment stages showed the most frequent aching pain
reports, the highest being on the first day after initial archwire insertion. As mentioned earlier the
type or quality of the pain experience did not change significantly between different orthodontic
procedures and during the insertion of initial archwire the distribution of the quality of pain changed
minimally, 65.2% for sore, 14.6% for shooting, 12.1% for dull and 8.1% for ache. The results
suggest that the type or quality of the pain experienced during orthodontic treatment does not
change significantly.
The first day after any of the orthodontic treatment stages had higher frequency of long duration
pain among the three days, with the highest recording being during the first day after initial
archwire insertion. An interesting observation is that the occurrence of the long duration of pain
also declined gradually from the first to the third day.
6.2.4. Analgesic consumption
The individual variation is reflected in the consumption of analgesics because it could be a matter of
whether a person preferred avoiding medicine or was keen on taking analgesics on a preventive
basis. Ideally an analgesic drug provides significant relief across all pain severities, has minimal
side effects, has few drug interactions and is convenient to administer (Altman 2004, Antman et. al
2007, Chang et. al 2005, Savage and Henry 2004, Zelenakas et. al 2004). Although somewhat a
coarse method for pain assessment analgesic consumption showed a similar pattern to the responses
from the questionnaires. In this sample, regression model showed that after the initial archwire
insertion T2 and archwire activation T4, there was a need for pain medication. At the peak of the
reported pain symptoms, during the initial archwire insertion 15 patients, about one in four, reported
the need for pain medication. However, during the separation of molars and wire activation the
corresponding number was only two. At the initial archwire insertion stage about one fourth of
patients reported taking medication with one patient taking three doses during the first day. The
demand for analgesics was limited to the first and second day during the separation of molars and
activation stage with no patient reporting having taken medication on the third day. However,
during the initial archwire insertion 5% of patients took medication for pain relief on the third day,
this is in agreement with the results from Jones (1984) and Scheurer et al. (1996). In contrast to the
findings of Feinmann et al. (1987) who reported no correlation between the pain experience and
analgesic consumption, in the present study a correlation was found between the total pain score
63
and the use of analgesics.
Ngan et al (1994) have reported that after one initial dose of analgesics at the moment of orthodon-
tic appliance insertion, none of the patients needed additional pain relief. Although in the present
study neither prescription for pain medication nor analgesics were dispensed to the patients, it is
possible that some patients consumed the analgesics as a preventive measure.
First and second days after either initial archwire insertion or archwire activation, provoked the
experienced pain and the need for analgesic.
6.2.5. Dental pain sites
Pain connected to orthodontic tooth movement most probably originates from the periodontal
tissues due to mechanical injury and consequent inflammatory reaction. However, also intradental
nociceptive nerves may be involved because periodontal inflammatory reactions may spread to the
pulp due to formation and diffusion of various inflammatory mediators, and neurogenic
inflammation mediated by branching axons, which are known to innervate both the pulp and
periodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b). Moreover, as already
mentioned, nerve sprouting also takes place within the pulp in response to orthodontic forces, which
may affect the functional properties of the intradental nerves. Also, possible impairment of the
pulpal blood flow due to vessel compression may play a role.
Chewing something fairly hard -a plastic wafer, for example- within the first two hours after arch
wire adjustment may act to reduce the ischemia and inflammation in the periodontal ligament
(Furstman and Bernick 1972). Stimulation of vascular and lymphatic circulation would prevent the
build-up of metabolic products, which are known to stimulate pain receptors (Proffit 1986).
The pain experienced during separation of the first molars understandably was related to the
mastication of food and fitting posterior teeth together. Interestingly fitting anterior teeth together
although not at a statistically significant level, was also affected to some extent with the placement
of orthodontic separators. Similar observations have been made by Ngan et al. (1989).
At the initial archwire insertion the responses were mostly concentrated in mastication, as well as
fitting anterior and posterior teeth together respectively. This is not surprising since insertion of the
archwire for initial alignment tends to increase the level of discomfort on the front teeth. This
64
finding is in agreement with previous studies (Ngan et al. 1989, Scheurer et al. 1996) and further
demonstrates the sensitivity of the questionnaire used in the present study.
A month later at the activation of archwire, however, the responses were different, fitting anterior
teeth was the most frequently recorded function inducing pain, followed by mastication of food. At
this stage the experienced pain caused by fitting posterior teeth together was at its lowest level,
which may suggest that as the orthodontic treatment progresses, at least during the initial stage,
there is a gradual decrease of the pain symptoms which seems to start from the posterior teeth.
6.2.6. Relationships between the pain symptoms during initial tooth movement
and age, gender, and treatment approach.
Over the years the question of whether or not age has an influence on perceived pain during
orthodontic therapy has remained controversial, partially due to the differences in study designs and
experiments. In this study, the clinical data indicates a higher discomfort experience in patients aged
16 and over than those of under, being at a statistically significant level in connection with incisors,
canines and premolars during activation of the archwire in response to cold stimulation at 15ºC.
This is in agreement with the findings of Jones (1984), Jones and Chan (1992).
It has been suggested previously that pain might be related to gender (Feinmann et al. 1987).
However, in the present study no statistically significant difference was found between genders in
the subsequent pain responses. Earlier reports seem to agree with this finding (Jones 1984, Ngan et
al. 1989, Jones and Chan 1992). However, Kvam et al. (1987), and Scheurer et al (1996), have
observed that females reported a higher impact on daily life from orthodontic appliances than
males.
Pain symptoms did not differ between extraction and non-extraction cases. Some orthodontists may
prefer to initiate the treatment of one arch at a time to alleviate the pain. Except for molars
responses to cold stimulation at 15ºC during the archwire activation indicating less sensitivity when
treating one arch, the results from this study did not indicate that this treatment strategy would
reduce the perceived pain/discomfort. This finding is in line with the findings of Scheurer et al.
(1996), and Jones and Chan (1992).
65
6.3. Clinical study
6.3.1. Electrical tooth stimulation
Electrical pulp testing methods were first developed in the 1860´s and since that time, many
different methods have been used (Lin and Chandler 2008), dealing with faradic current, galvanic
current, direct, alternating, or high frequency alternating current (Burnside et al. 1974). Electrical
stimulation is convenient in that the stimulus intensity needed to evoke a sensory response can be
determined accurately. The end point of electrical stimulus determination is a threshold sensation,
prepain. Mumford (1973) stated, "Electrical stimuli are at once the most natural and the most artifi-
cial of the stimuli applied to the teeth. They are natural in that conduction through the tissues is
electrolytic, depending on ionic movement, and ionic movement is fundamental to nerve excitation.
They are artificial in that electrical stimuli not applied to the teeth in the natural way that thermal
stimuli are when eating and drinking. However, electrical stimuli have the great advantage over
other stimuli that they can be precisely defined by electronic methods."
Constant current stimulator used in the present study had optimal output characteristics with 10 ms
cathodal square wave pulses (Björn 1946, Mumford and Björn 1962, Mumford 1982). Matthews
and Searle (1974) have investigated seven different pulp testers and reported Bofors® pulp tester
(the electrical stimulator used in the present study) to be the most reliable. Constant current
stimulator minimizes the effect of possible variations in the impedance of the stimulation circuit
(Mumford 1982). If the stimulation were not of constant current type, any changes in the impedance
of stimulation circuit would result in a change in the effective (stimulating) current intensity in the
pulp (Kontturi-Närhi 1993). The current density in the area of the nerve fibers is decisive for their
activation (Mumford 1982). Thus, measurement of voltage in the teeth is unsatisfactory, voltage
drop may vary because of variations in electrical resistance of the dental hard tissues. In addition,
cracks, pits, fissures, caries, restorations, and fractures may cause variations in electrical resistance.
Therefore, in order to overcome such variations in resistance, a stimulator that measures current
rather than voltage should be used.
During the stimulation of teeth the electrode was in contact to the incisal/occlusal third on the
lingual surface of the teeth, cervical stimulation was avoided because of the possibility of current
leakage to the soft tissues with the low resistance (Mumford and Björn 1962, Matthews and Searle
1974, Mumford 1982). The lingual surfaces were used for electrical stimulation to avoid possible
interferences from the brackets. In the view of the fact that all efforts on the part of examiner were
made to isolate the teeth from saliva and tongue, there were cases especially in the lower jaw that
66
made this task difficult. Saliva would provide a current leakage to the soft tissues therefore
increasing the readings significantly. Thus each tooth was tested twice at any given session and if
the difference between the two recordings more than 10 µA for incisors, more than 15 µA for
canines and premolars and more than 25 µA for molars the lower value was taken for statistical
analysis instead of taking a mean value.
Teeth which were not fully erupted were excluded from the clinical testing, because the larger the
quantity of pulp tissue the the amount of electrical current
passing through a unit area in the pulp is greatest where the pulp tissue is thinnest (Hargreaves
1973). There was no statistically significant differences between the maxillary and mandibular
dental electrical thresholds, thus they were combined. Teeth were further grouped as recommended
by Mumford (1982) in the following order, 1) incisors, 2) canines and premolars and 3) molars.
smaller is the electrical impedance,
Nordh (1955) used the Björn pulp tester for testing 36 teeth on the same day before and after orth-
odontic band placement and reported no significant difference in the perception thresholds. He also
tested 13 teeth (with a control group of 10) before and after orthodontic space closure and found no
significant differences. Burnside et al. (1974) reported higher pain threshold values to electrical
stimulation in the experimental group, however the comparison was made between patients who
had fixed orthodontic appliances for a minimum of four months prior to testing and a control group
without any appliances.
Effectiveness of an electrical current in stimulating a tooth does not depend on the presence of
receptors at the pulp dentin junction, this activation likely occurs on more central component of the
axons in dental pulp (Mumford 1982, Närhi 1985b). Mumford (1982) has further reported teeth
with hyperemia or acute pulpitis not to have a lower electrical threshold. Therefore, the electrical
threshold determination does not give much if any information on the receptor sensitivity. Kontturi-
Närhi (1993) has also reported similar findings. Because of the longitudinal nature of this study and
tooth responses to orthodontic forces and pulpal tissue reaction to such forces (i.e. hyperemia), an
interesting objective of the present study was to find out if there were any changes in electrical
thresholds of the teeth. However, the results have clearly demonstrated that dental electrical thresh-
olds were generally constant, before, during and after different orthodontic treatment procedures.
67
6.3.2. Cold sensitivity tests
Cold has been reported to be the most potent irritant in inducing pain in hypersensitive teeth
(Naylor 1961, Brännström 1981, Dowel et al. 1985, Flynn et al. 1985, Närhi 1985a, Orchardson and
Collins 1987a,b, Kontturi-Närhi 1993). Extreme cold for pulp vitality test has long been in use.
Saxer (1958) using dry ice or carbon dioxide snow for pulp vitality test, reported in 1000 teeth an
accuracy of 97.5%, compared to 97.2% for electrical pulp testing. Although the temperature of
carbon dioxide snow is -78ºC, Augsburger and Peters (1981) found that the intra pulpal tempera-
ture, as measured in vitro, decreased only by a mean value of 15.6ºC for non-carious teeth. Their
clinical studies indicated that a 2-second exposure was sufficient to produce a sensory response.
The present study is the first in the orthodontic literature to have extensively investigated pulpal
reaction to orthodontic tooth movement. Additionally, it is the first to use an accurate and reliable
electrothermal device for evaluation of the intensity of orthodontic related pain symptoms.
The electorthermal device used in the present study for the cold stimulation was constructed at the
Technical Center of the University of Kuopio, Finland. The reliability of a similar device has been
confirmed previously and cold stimulation was found to be the most suitable for dentin sensitivity
tests (Kontturi-Närhi 1993). The desired temperature could be adjusted with an accuracy of 0.1ºC,
which is more than satisfactory for the clinical tests. The size of the stimulator tip was suitable
having a sufficient thermal capacity and allowing a good access to the teeth. The thermal
stimulator’s tip was flat, the contact area varied considering the shape of the tooth surface. This
may have caused variations in the stimulus applied. However, this variation was acceptable because
of the good correlation between the responses to cold stimulation at the different temperatures
studied.
Visual Analogue Scale (VAS) was used to evaluate the intensity of the induced pain during the cold
stimulations. This method is widely used for measuring pain and has been described by other
investigators as being sensitive and reliable and also having certain advantages over verbal scales
(Uskisson 1974, Huskisson 1983, Seymour et al. 1985, McGrath 1986, Duncan et al. 1989). VAS is
a direct rating scale and offers a continuum of different pain intensity levels (Huskisson 1983) and
accordingly allows the use of parametric statistical tests (Bhat 1986).
Cold stimulation at 0ºC induced more pain than at 15ºC before, during and after application of
orthodontic forces during the study. The pain responses to clinical examinations at 0ºC and 15ºC,
68
interestingly, were corresponding to the fluctuation of the pain experience as reported by the
patients in response to the questionnaire. Also the subjective pain reports indicated the initial
archwire insertion to be the most painful stage of treatment. The cold responses were the most
intense in incisors, canines/premolars and molars respectively. The incisors which were the most
sensitive tooth group to cold showed the most intense pain responses during initial archwire inser-
tion which is in agreement with the questionnaire results.
Although, the proportion of teeth responding to cold stimulation at 15ºC was significantly lower
than at 0ºC, by no means this test is less effective in its ability to distinguish between different
stages of treatment. Using paired t-test revealed that responses of the first molars to cold stimulation at
0ºC, also incisors, canines and premolars at 15ºC were at a statistically significant level when
comparing the initial archwire insertion to other stages of the orthodontic treatment.
An interesting observation was that when considering cold stimulation at 0ºC only molars were
found to be responding at a statistically significant level. However, during cold stimulation at 15ºC
such differences were exclusive for incisors, canines and premolars. One explanation for the
differences could be that two seconds of cold stimulation at 15ºC for molars was not sufficient for
the differentiation of responses considering the thickness of the enamel and dentin of such teeth. On
the other hand cold stimulation at 0ºC was able to differentiate the most sensitive stage (initial
archwire insertion) from all other stages. Looking at the responses from incisors, canines and
premolars, it seems that cold stimulation at 0ºC although evoked more responses overall (28.2%-
34.6%) than 15ºC (6.25%-11.7%), it might have been too strong a stimulus for patients’
discriminatory ability to differentiate among different stages of the treatment. However, cold stimu-
lation of incisors, canines and premolars, at 15ºC was able to differentiate the sensitivity changes
during different procedures of orthodontic therapy.
Although the changes in the dental cold sensitivity during orthodontic treatment were small they
indicate that part of the discomfort and pain experienced by the patients may, in fact, be of pulpal
origin. It has been shown that morphological changes in the pulpal innervations can be induced by
orthodontic forces (Yamaguchi and Kasai 2005). The sensitivity changes found in the present study
may be related to such morphological nerve responses.
69
6.3.3. Comparison of different fixed orthodontic appliances
Both techniques under trial in this study used light continuous forces. Aside from the obvious
differences in the bracket designs, there are two major differences between the two approaches.
First, the dimension and the amount of the force delivered by different initial archwires and second,
the use of closed coils in extraction cases.
Using the Irregularity Index there was no statistically significant difference between the two fixed
appliance groups prior to orthodontic treatment.
The decisions for extraction of teeth were made either to relieve the severely crowded dental arches
and/or to reduce the excessive over jet and/or over bite. Although, all extraction spaces were
completely closed by the end of the orthodontic treatment, the study period considers only the tooth
movements, which occurred during the first three months of the treatment, and compared the tooth
movements accordingly.
One difference was the timing of the application of force, for canine retraction in extraction cases.
Because, as shown by Quinn and Yoshikawa (1985), once the force threshold for tooth movement is
reached, the magnitude of the force applied to the teeth becomes less important. Therefore, using
light forces to have a control of the unwanted movement of the anchor teeth is a fact, which was
taken into account and in the sample studied. Although not separately studied, clinically there was
no evidence of anchorage loss.
Generally, the results of the present questionnaire study indicated no statistically significant
differences in terms of the pain experienced, in either of the initial archwires or their activation
stages between the two techniques. Patients inability to distinguish between the two light
continuous force systems used in the study, is in line with the previous findings (Boester and
Johnston 1974, Andreasen and Zwanziger 1980, Jones and Richmond 1985, Jones and Chan 1992,
Scott et al. 2008). Using the Irregularity Index (Little, 1975) for evaluating the anterior crowding
revealed no statistically significant difference between the two techniques. This finding is also
supported by the conclusion of O´Brien et al. (1990). In extraction cases using closed coils at the
initial stage increased tooth movement was observed during the period of three months. It is a fact
that at present no archwire is "ideal" for all type of orthodontic tooth movement. This is not
surprising because the demands of the treatment plan require different characteristic stiffnesses and
ranges (Kusy 1997).
70
Results from the thermal sensitivity tests using Visual Analogue Scale (VAS) have indicated that
the differences between the groups were altogether small and do not as such justify too extensive
comparison of the two techniques.
Ideally the orthodontic forces should be kept to a level below the pain threshold of each individual
patient. Our results indicate that slight difference in the forces applied, assuming it is within the
recommended range, type and duration, during the initial phase of the orthodontic treatment is not
directly related to the pain experienced by the patients and the tooth sensitivity. Obviously, there is
a difference in the timing of the force application in extraction cases between the two techniques,
and the picture becomes more complicated when we consider the type of tooth movement, for
example, tipping and rotation. Further study is necessary to answer these questions. In light of the
present results it is therefore recommended that the bracket design and ligation system should be
modified in such a way that can accommodate and take advantage of the ever changing new
information and wire technology.
71
7. SUMMARY AND CONCLUSIONS
The present study was performed to assess the experienced pain as reported by the patients at
different stages of orthodontic treatment. It was also examined if orthodontic forces and tooth
movement affect the dental pulp sensitivity, and if such sensitivity is related to the pain experience.
The study subjects were 64 orthodontic patients, 46 females and 18 males, with the mean age of
26.4 (SD 11.2) years and range of 10.8-49.3 years. The sample consisted of consecutive cases of
patients who were willing to participate in the study. A structured questionnaire was used to map
the prevalence, intensity, quality and duration of pain/discomfort after separation of first molars,
after the initial archwire insertion and after the first activation of the archwire, for three days after
each stage. Dental electrical thresholds were measured using an electrical pulp tester and thermal
sensitivity measurement was carried out with an electrothermal device at 15ºC and 0ºC. The
intensity of the pain induced by cold stimulation was assessed using a 100 mm Visual Analogue
Scale (VAS). Deciduous teeth were excluded from the clinical measurements. Altogether 907
permanent teeth of 64 patients were measured at all stages of the study. Tooth movement (mm) was
measured from the hard stone casts using the Irregularity Index (Little 1975). Additionally, two
different orthodontic techniques, namely those of the Alexander and the Viazis, were compared for
the pain experienced, dental sensitivity to cold stimulation and electrical thresholds as well as for
the rate of the tooth movement.
The prevalence of the pain reports according to the questionnaire was higher after the initial
archwire insertion (96%) than after the separation of the first molars (70%) or the archwire
activation (69%). The first day after any of the three orthodontic treatment stages had the most
frequent pain experience, the highest being on the first day after initial archwire insertion. The most
common stimuli related to pain during the first three days after the initial archwire insertion were:
1) mastication of food in 90.2% of the subjects 2) fitting anterior teeth together in 82.7% 3) fitting
posterior teeth together in 78.6% 4) tooth brushing in 47.6% 5) cold food/drink in 27.4% 6) hot
food/drink in 22.3% and 7) sweets in 9.8%. Longer duration of the experienced pain was reported
during the first day after any of the orthodontic procedures, the highest being recorded during the
first day after the initial archwire insertion. The perceived pain decreased significantly from the first
to the second and further to the third day after each orthodontic procedure.
The intensity of the reported pain during the study period was most often mild, in 62.5% of the
reports followed by moderate pain in 28.5% and severe pain in 9%. The pain reported by the
patients after different orthodontic procedures was most often described as sore (63.5%), followed
72
by shooting (14.3%), dull (14.3%) and aching (7.9%) pain. Generally, the quality or type of the pain
symptoms remained constant during the initial stage of orthodontic treatment. The duration of the
pain symptoms reported after different orthodontic procedures was usually short, in 85% of the
reports, compared to long duration found in 15%.
The analgesic consumption showed a similar pattern as the prevalence and intensity of the pain
reports. In general, patients who consumed analgesics reported more pain symptoms.
There were no statistically significant differences between the reported pain and gender, extraction
versus none extraction, type of fixed appliance, or treatment of one or both arches. Although, not at
a statistically significant level, the data indicates a higher discomfort experience in patients aged 16
and over, compared to the younger subjects.
The lack of changes in response to dental electrical stimulation during the study period may suggest
a poor relationship between the dental electrical threshold and the possible changes in the dental
pulp after the application of orthodontic forces. However, It is also possible that the extent of which
the dental pulp is affected by the orthodontic forces is simply not enough to change its electrical
thresholds.
The proportion of teeth responding to the cold stimulation at 0ºC was higher than at 15ºC, and the
pain ratings measured using the Visual Analogue Scale were significantly higher for 0ºC. Cold
stimulations at 0ºC and 15ºC, interestingly, correspond to the results from the questionnaire,
indicating the pain experienced after the initial archwire stage to be the most intense. It was
demonstrated that there is a change in cold sensitivity of the dental pulp subsequent to orthodontic
treatment and that such sensitivity is highest after the initial archwire insertion.
Cold stimulation at 0ºC and 15ºC induced pain (all tooth groups combined) in 28.6% and 6.2%
before the treatment, 34.6% and 11.7% three days after the initial archwire insertion followed by
30.9% and 6.9% before the archwire activation stage, and 28.2% and 9.5% three days after
activation, respectively. Incisors were the most sensitive group of teeth, showing the most frequent
response 47.7%, the highest pain scores at 0ºC three days after the initial archwire insertion, which
is in agreement with the questionnaire results. The differences of the first molars VAS scores to
cold stimulation at 0ºC were at a statistically significant level when comparing initial archwire
insertion stage to: initial (p=.024), separation of molars (p=.013), activation (p=.019) and three days
after activation (p=.017), stages. The differences in the incisors responses to cold at 0ºC between
73
initial stage and initial archwire stage, (p=.079) showed a tendency to increase in sensitivity,
although, not at a significant level. Statistically significant differences at 15ºC (paired t-test) were
found between the initial stage and the initial archwire insertion in, incisors (p=.042), canines +
premolars (p=.026), between initial archwire and activation stage in, canines + premolars (p=.002),
between activation and three days after activation in, canines + premolars (p=.036). The incisors
responses between the initial archwire and the activation stage followed the same pattern, although,
the difference was not statistically significant (p=.065).
In general the differences in the prevalence of pain between the two different fixed appliances were
small and statistically significant only in connection with some of the questionnaire items, which
altogether gave the most frequent pain reports. Such items were mastication, as well as fitting
anterior and posterior teeth together. Results from the thermal sensitivity tests using Visual
Analogue Scale (VAS) have indicated that the differences between the groups were altogether small
and do not as such justify too extensive comparison of the two techniques.
Comparing orthodontic tooth movements with different fixed appliances, using the irregularity in-
dex (Little 1975) for the maxillary and mandibular anterior crowdings (canine to canine) showed no
statistically significant difference between the two fixed orthodontic appliances. In extraction cases,
increased orthodontic tooth movement was observed using the closed coils.
74
On the basis of the present study, the following conclusions can be drawn:
Orthodontic treatment generally induces pain and discomfort, which could mostly be categorized as
mild and short lasting. However, some patients do experience severe pain during the treatment even
to the extent that, mastication of food and tooth brushing might be impaired.
Pain is experienced after orthodontic procedures at different stages of treatment. Analgesic
consumption is correlated with the intensity of the pain experienced. Depending on the patients pain
threshold, clinicians should consider prescribing pain medication to alleviate the unpleasant
experience. The pain experienced during orthodontic treatment originates mostly from periodontium, due to
mechanical injury and consequent inflammatory reaction. Pulpal changes do not seem to contribute
significantly to the patient`s overall pain experience. However, sensitivity of teeth to cold
stimulation during the treatment correlates to the pain responses from the questionnaire study,
suggesting that responses in the dental pulp also play a role. No correlation was found between the
electrical stimulation of teeth and the pain responses from the questionnaire study. Inability of patients to distinguish between different light continuous forces during the initial phase
of the orthodontic treatment was observed. Neither the pain experienced by patients nor the tooth
sensitivity was affected by different archwires used in the present study. Amount of tooth
movement, during the initial phase of the orthodontic treatment does not seem to be directly related
to the pain symptoms experienced by the patients.
75
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93
APPENDIX I
The questionnaire used in the present study. Stimulus
Sore
Shooting
Dull
Ache
Sweets
0 Duration 1 S 2 L 3
0 Duration 1 S 2 L 3
0 Duration 1 S 2 L 3
0 Duration 1 S 2 L 3
Hot, Food/Drink
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
Cold, Food/Drink
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
Tooth brushing
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
Mastication of Food
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
Fitting anterior teeth together
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
Fitting posterior Teeth together
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
0 1 S 2 L 3
94
APPENDIX II
Associations between the subjective pain reports and clinical measurements
Assessment of the possible associations between the subjective pain reports (the questionnaire
study), and clinical measurements (cold tests 15/0ºC and electrical vitality tests µA), was
further studied.
Multiple regression analyses were used to estimate the associations between the pain
experienced at different stages of orthodontic treatment (Index 3, 0-504) namely after
separation of the first molars, after initial archwire insertion and after initial archwire activation
and cold sensitivity tests at 15ºC and 0ºC (mean VAS values, 0-100 mm), electrical vitality
tests (mean, 0-125 µA), in different tooth groups (1.Incisors, 2. Canines and Premolars, 3.
Molars), considering the effects of age (1<16, 2≥ 16 years), gender (0=female, 1=male),
extraction of teeth (0=no, 1=yes), fixed appliances used for orthodontic treatment (1=
Alexander, 2=Viazis), analgesic consumption (0=no, 1=yes), one or both jaws treatment
(1=maxillary or mandibular, 2=both jaws). Due to high correlation between different tooth
groups in cold and electrical measurements, as well as, cold measurements between 15ºC and
0ºC, separate regression models were prepared. There were no statistically significant
differences between the pain experienced after separation of molars and the independent
variables (Table.14).
Medication for the management of pain during the first three days after the initial archwire
insertion and the archwire activation was statistically significant in the tooth groups in both of
the models. Pain experienced by patients aged 16 years and over after archwire activation stage
in both incisors, canines and premolars tooth groups, in model A, was statistically significant.
Statistically significant associations were found in relation to all the tooth groups after the
activation of archwire and molars after the initial archwire insertion and cold measurements.
Treatment of both jaws in response to molars was statistically significantly associated with the
model A.
95
Association between the reported pain after the insertion of initial archwire stage, activation of
archwire stage, and independent variables. Cold and electrical measurements are from different
tooth groups; 1) central and lateral incisors, 2) canines and premolars, 3) molars. (Cold
measurements at 15ºC in Model A and at 0ºC in Model B). Only statistically significant
differences are given.
Tooth groups Treatment stage/ Independent variables
Model A Regr. coeff. P
Model B Regr. coeff. P
Incisors
After initial archwire/ Analgesic consumption
49.8
.008
49.8
.008
After archwire activation/ Age
1.5 .045
Analgesic consumption 103.9 .004 76.9 .019 Cold VAS (mm) 2.2 .043 1.3 .003 Canines/premolars After initial archwire/
Analgesic consumption 49.8
.008
49.8
.008
After archwire activation/ Age
1.4 .049
Analgesic consumption 110.6 .002 101.9 .002 Cold VAS (mm) 7.8 .018 3.1 .001 Molars After initial archwire/
Analgesic consumption 45.3
.015
54.7
.007
Cold VAS (mm) 5.5 .019 After archwire activation/
Treatment of one or both jaws 40.5
.008
Analgesic consumption 67.6 .037 104.7 .000 Cold VAS (mm) 2.8 .000
96
APPENDIX III
The mean values of VAS pain ratings to 15ºC cold stimulation at different stages of the
orthodontic treatment are presented. Incisors were the most sensitive during the trial period
followed closely by canines, premolars and molars. No significant statistical differences were
found between maxillary and mandibular teeth responses at different stages of the treatment
using the paired t-test. molars. Statistically significant differences (paired t-test) were found
between initial stage and initial archwire stage in, incisors (p=.042), canines + premolars
(p=.026), between initial archwire and activation stage in, canines + premolars (p=.002),
between activation and three days after activation in, canines + premolars (p=.036). Although,
not statistically significant (p=.065), the incisors responses between the initial archwire and the
activation stage followed the same pattern.
0
25mm
654321
The mean VAS pain ratings to 15ºC cold stimulation at different stages of the orthodontic
treatment (I = initial, II = separation of molars, III = three days after the initial archwire
insertion, IV = before wire activation and V = three days after activation) in maxillary and
mandibular teeth (1 = incisors, 2 = laterals, 3 = canines, 4 = first premolars, 5 = second
premolars and 6 = molars).
maxilla
mandible
25
I II III IV V
97
APPENDIX IV
The mean values from VAS pain ratings to 0ºC at different stages of the treatment are
presented. The VAS pain ratings to cold at 0ºC were higher compare to 15ºC at all the stages of
treatment. Maxillary molars showed a higher VAS ratings than mandibular molars at all the
stages being at a statistically significant level, also mandibular central incisors had VAS ratings
higher than maxillary central incisors at the activation stage (p<.05). Paired t-test revealed that
the difference in the molars responses to cold stimulation (0ºC) were at a statistically signifi-
cant level when comparing initial archwire insertion to: initial stage (p=.024), separation stage
(p=.013), activation stage (p=.019) and three days after activation (p=.017). The incisors
responses to cold at 0ºC between initial stage and initial archwire stage, also showed a
substantial increase in the sensitivity, although the difference was not significant (p=.079).
0
25mm
654321
I II III IV V
25
maxilla
mandible
The mean VAS pain ratings to 0ºC cold stimulation at different stages of the orthodontic
treatment (I = initial, II = separation of molars, III = three days after the initial archwire
insertion, IV = before wire activation and V = three days after activation) in maxillary and
mandibular teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first premolars, 5 =
second premolars and 6 = molars).
98
APPENDIX V
The dental electrical thresholds at different stages of the treatment are shown. The mean
electrical threshold values at the initial measurement in µA for the maxillary arch, were 28.7 in
molars, 20.5 in second premolars, 18.5 in first premolars, 14.5 in canines, 12.3 in lateral in-
cisors, 11.9 in central incisors, and for the mandibular arch 29.3 in molars, 22.7 in second
premolars, 23.1 first premolars, 19.2 canines, 14.9 in lateral incisors, 15.2 in central incisors.
The differences in the mean thresholds between the maxillary and mandibular teeth were not
statistically significant. Therefore the combined mean electrical threshold values from the
maxillary and mandibular teeth were used for further statistical analysis. As with the cold
responses the results of electrical stimulation were studied with respect to different tooth groups
(1= incisors, 2= premolars and canines, 3= molars).
The mean electrical thresholds of teeth at different stages of orthodontic treatment (I = initial, II
= three days after the separation of the first molars, III = three days after the initial archwire
insertion, IV = before wire activation and V = three days after activation) in maxillary and
mandibular permanent teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first
premolars, 5 = second premolars and 6 = first molars).
0
30µA
654321
maxilla
mandible
I II III IV V
99
30
Kuopio University Publications D. Medical Sciences D 434. Hassinen, Maija. Predictors and consequences of the metabolic syndrome: population-based studies in aging men and women. 2008. Acad. Diss. D 435. Saltevo, Juha. Low-grade inflammation and adiponectin in the metabolic syndrome. 2008. 109 p. Acad. Diss. D 436. Ervasti, Mari. Evaluation of Iron Status Using Methods Based on the Features of Red Blood Cells and Reticulocytes. 2008. 104 p. Acad. Diss. D 437. Muukka, Eija. Luomun tie päiväkotiin: luomuruokailun toteutettavuus ja ravitsemuksellinen merkitys päiväkotilapsille. 2008. 168 p. Acad. Diss. D 438. Sörensen, Lars. Work ability and health-related quality of life in middle-aged men: the role of physical activity and fitness. 2008. 83 p. Acad. Diss. D 439. Maaranen, Päivi. Dissociation in the finnish general population. 2008. 97 p. Acad. Diss. D 440. Hyvönen, Juha. Suomen psykiatrinen hoitojärjestelmä 1990-luvulla historian jatkumon näkökulmasta. 2008. 279 p. Acad. Diss. D 441. Mäkinen, Heidi. Disease activity and remission in rheumatoid arthritis: comparison of available disease activity measures and development of a novel disease sctivity indes: the mean overall index for rheumatoid arthritis (MOI-RA). 2008. 129 p. Acad. Diss. D 442. Kousa, Anne. The regional association of the hardness in well waters and the incidence of acute myocardial infarction in rural Finland. 2008. 92 p. Acad. Diss. D 443. Olkku, Anu. Glucocorticoid-induced changes in osteoblastic cells: cross-talk with wnt and glutamate signalling pathways. 2009. 118 p. Acad. Diss. D 444. Mattila, Riikka. Effectiveness of a multidisciplinary lifestyle intervention on hypertension, cardiovascular risk factors and musculoskeletal symptoms. 2009. 92 p. Acad. Diss. D 445. Hartmann-Petersen, Susanna. Hyaluronan and CD44 in epidermis with special reference to growth factors and malignant transformation. 2009. 103 p. Acad. Diss. D 446. Tolppanen, Anna-Maija. Genetic association of the tenomodulin gene (TNMD) with obesity- and inflammation-related phenotypes. 2009. 111 p. Acad. Diss. D 447. Lehto, Soili Marianne. Biological findings in major depressive disorder with special reference to the atypical features subtype. 2009. 115 p. Acad. Diss. D 448. Nieminen, Jyrki. Effect of functional loading on remodelling in canine, and normal and collagen type II transgenic murine bone. 2009. 107 p. Acad. Diss. D 449. Torpström, Jaana. Yliopistokoulutus ravitsemusasiantuntijuuden kehittäjänä. 2009. 164 p. Acad. Diss.