Original Article

Clinical Evaluation of a 3% Potassium Oxalate Geland a GaAlAs Laser for the Treatment

of Dentinal Hypersensitivity

Alessandra Helen Magacho Vieira, M.Sc.,1 Vanara Florencio Passos, M.Sc.,1

Jorgiana Silva de Assis, D.D.S.,1 Juliano Sartori Mendonca, D.D.S.,2 and Sergio Lima Santiago, D.D.S.1

Abstract

Objectives: This study evaluated the immediate and 3 month clinical effects of a low-level gallium-aluminum-arsenide (GaAlAs) laser and a 3% potassium oxalate gel for the treatment of dentinal hypersensitivity. Materialsand Methods: A total of 164 teeth from 30 patients with clinical diagnoses of dentinal hypersensitivity wereselected for this randomized, placebo-controlled, double-blind clinical study. The teeth were randomized tothree groups: GaAlAs laser, oxalate gel, and placebo gel. The treatment sessions were performed at 7 d intervalsfor four consecutive weeks. The degree of sensitivity in response to an air blast and tactile stimuli was assessedaccording to a visual analogue scale at baseline, immediately after the fourth application, and then 3 months afterthe fourth application. The reductions in dentinal hypersensitivity from baseline at the two follow-up assess-ments were evaluated as the main outcome. Results: In both the active and control groups, there were statis-tically significant reductions in dentinal hypersensitivity immediately after and 3 months after the treatments,when compared with the hypersensitivity at baseline. No significant differences among the three groupscould be detected in their efficacy at either the immediate or 3 month evaluations irrespective of the stimulus.Conclusions: The treatments under study were effective for reducing dentinal hypersensitivity, and longer ob-servational periods could enhance the ability of studies to detect differences between active and placebo groups.

Introduction

Dentinal hypersensitivity is an exaggerated responseto sensory stimuli that usually causes no response in a

normal, healthy tooth.1 It is perceived as a localized, rapidlydeveloping, and transient pain, and it is associated withdentin exposure to the oral environment.1,2 Dentin exposurecan result from enamel loss by erosion, abrasion, abfraction,or denudation of root surfaces as a result of gingival recessionor periodontal procedures.3–6

Prevalence studies indicate that dentinal hypersensitivityaffects 10–30% of various populations,1,2,7,8 and a similarprevalence was observed in a Brazilian population.9 More-over, with teeth being preserved and retained for longerperiods, there will be increasing demand for treatment bypatients with this condition,1,2 particularly in developingcountries, where life expectancy is increasing. Dentinal hyper-sensitivity is the most frequent complaint among reportedodontalgias.10 Depending on its intensity, the hyperesthesiacan affect eating, drinking, and breathing, hinder the ability

to control dental plaque effectively, and, sometimes, it mayeven result in emotional changes that alter lifestyle.1

The hydrodynamic theory is the most widely acceptedhypothesis to explain how stimuli applied on the dentinsurface influence nerve fibers.2,6,11–13 The painful sensation isthought to arise from the exposed dentin after sensorialstimulation through the rapid fluid movement in either aninward or outward direction inside the dentinal tubules.11

The fluid displacement within the tubules determines thevariation in the intrapulpal pressure that stimulates thenerve endings located at the pulp–dentin interface and, thusresults in the generation of pain impulses.11,13

Historically, several desensitizing agents have been usedfor treating this problem, including hot oil, arsenic, silvernitrate, and formaldehyde.5,14 Recently, other types oftreatments, such as oxalate gels and application of laserbeams, have emerged and have been shown to be signifi-cantly effective in reducing hyperesthesia.5,6,10,13–30

Potassium oxalate formulations have been tested in labo-ratory and clinical studies.4,5,14,21,23,25–28,30 The application of

1Department of Restorative Dentistry, Federal University of Ceara, Fortaleza, Ceara, Brazil.2Department of Dentistry, University of Fortaleza, Fortaleza, Ceara, Brazil.

Photomedicine and Laser SurgeryVolume 27, Number 5, 2009ª Mary Ann Liebert, Inc.Pp. 807–812DOI: 10.1089=pho.2008.2364

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oxalates on hypersensitive surfaces mainly results in theprecipitation of insoluble calcium oxalate crystals that oblit-erate patent dentinal tubules and thereby control the perme-ability of exposed dentin.5,14,23–26 Based on the hydrodynamictheory, this reduction in permeability by the crystal deposi-tion of the fluid movement within the dentin proportionallydecreases the degree of pain.5,14,23,26

A new therapeutic approach for dentinal hypersensitivitywas developed with the advent of laser technology that isincreasingly used in dentistry.10,15–20,22,29 Low-level lasertherapy can occlude dentinal tubules by increasing the cel-lular metabolic activity of odontoblasts that promote tertiarydentin production.31

A review of the literature shows a great number oftreatment modalities for dentinal hypersensitivity, and thissuggests that none of the treatments are totally effec-tive.2,4,14,15,18,32 Currently, there is no desensitizing agent thatis considered ideal for managing this complex sensorial con-dition.7,10,14,15,18 Clinical trials have supported different ap-proaches, and the results have been contradictory.33,34 Inaddition, the placebo effect has to be taken into considerationbecause several clinical investigations have reported on itssignificant role.4,16,20,32

Therefore, controlled randomized studies of the effective-ness of desensitizing agents are important and much need-ed.3,15 The purpose of this study was to assess, at differentexamination periods, the clinical effects of a low-levelgallium-aluminum-arsenide (GaAlAs) laser and a 3% po-tassium oxalate gel for treating hypersensitive teeth, using aplacebo gel as a control.

Materials and Methods

A total of 164 teeth from 30 patients (7 men and 23women, aged between 24 and 68 years) with clinical diag-noses of moderate or severe dentinal hypersensitivity wereselected and enrolled. To participate in the trial, patients hadto have good oral hygiene and at least three hypersensitiveteeth, especially canines and premolars. Patients who pre-sented with severe systemic and=or psychological diseases,constant use of analgesic and=or anti-inflammatory drugs, orallergic responses to dental products were excluded. Also, inthe 6 months before enrollment, the individuals should nothave used any desensitizing agents and=or submitted toperiodontal surgery or scaling. The selected teeth had nocarious lesions, defective restorations, cracks or fractures,premature contact, prosthesis or orthodontics appliances,periodontal pockets, mobility, or evidence of pulpits. Parti-cipants were informed about the purpose and design of theinvestigation and signed an appropriate informed consentform. Standard dentifrices, toothbrushes, and instructionswere given to all subjects. The research protocol was ap-proved by the Committee of Ethics in Research of FederalUniversity of Ceara.

In order to blind both the participants and investigators tothe treatments, the two gels had the same color and textureand were dispensed in standard syringe with the purpose ofmasking the operator and not allowing identification of theproducts. In addition, for constituting a placebo for the lasertreatment, the laser was positioned and not activated ingroups assigned to placebo and oxalate gels. Thus, the ex-perimental model was split-mouth, placebo-controlled, and

double-blinded (although the study was simple-blinded forthe laser treatment, since the laser operator had to know forwhich group to activate the laser). The equipment and sub-stances used in the study included a low-level GaAlAs diodelaser device (Bio Wave LLLT Dual�; Kondortech EquipOdontologicos Ltda., Sao Carlos, Sao Paulo, Brazil), a 3% po-tassium oxalate gel (Oxa-Gel�; Kota Import’s Ltda., Sao Paulo,Sao Paulo, Brazil), and a placebo gel (ARTPELE Farmacia comManipulacao Ltda., Fortaleza, Ceara, Brazil) containing thesame composition of the potassium oxalate gel except for theactive substance. The 164 teeth (23 incisors, 20 canines, 77premolars, 44 molars) were randomly divided into threegroups according to the desensitizing treatment under study:laser treatment, potassium oxalate gel treatment, and placebogel treatment (Table 1). This randomization was performed byplacing all the selected teeth in a list and assigning treatmentaccording to a predefined sequence: 1) laser, 2) potassiumoxalate gel, and 3) placebo gel. Moreover, where possible, thethree different treatments were assigned to the same patient sothat the teeth had the same sensitivity thresholds.

The degree of sensitivity was determined for each tooth inresponse to tactile (probe) and air blast stimuli. The probestimulus was applied under slight manual pressure in themesiodistal direction on the cervical area of the tooth. The airblast was performed with an air syringe for 1 sec at a dis-tance of 1 cm from the tooth surface. Dentinal hypersensi-tivity was assessed by patient’s indication of the amount ofpain related to each tooth immediately after each stimulus,according to a visual analogue scale (VAS). The VAS was10 cm long and, on the left and right ends, contained anindication of ‘‘no pain’’ and ‘‘severe pain,’’ respectively. Theparticipants were instructed to place a mark on this 10 cmline that corresponded to the pain severity of each toothelicited by the hydrodynamic stimuli. The sensitivity pat-terns were recorded at baseline and immediately after and3 months after treatment by an examiner previously cali-brated for applying the stimuli. The order in which the teethwere evaluated within each subject was maintained at eachvisit. The examiner and the patients did not know whichtype of treatment was applied to each tooth.

The treatments were applied under relative isolation byone experienced operator other than the examiner. The diodelaser device was used on contact mode with the followingparameters: continuous emission, 30 mW output power,wavelength of 660 nm, irradiation time of 120 sec, and raydiameter of 3 mm resulting in an energy density of 4 J=cm2.The laser beam was applied with the laser tip positionedperpendicularly to the tooth surface at four points: one to theapex (apical point) and three to the cervical area (mesio-buccal, disto-buccal, and lingual points) of the tooth. Po-tassium oxalate gel was applied according to manufacturer’s

Table 1. Number of Teeth Assigned to Each Group

by Tooth Type

Tooth type Laser group Oxalate group Placebo group

Incisor 10 8 5Canine 6 8 6Premolar 28 24 25Molar 14 15 15

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instructions: passive application, using a brush, for 2 min.During this period, the laser device was positioned but notactivated. The placebo gel application followed this sameprocedure and the laser device was also positioned but notactivated. The treatment was repeated at 7 d intervals forfour consecutive weeks. Three months after the fourthtreatment session, patients were recalled for reassessment ofdentinal hypersensitivity.

Statistical analysis

The mean values of the clinical parameters were calculatedfor the three groups according to the different stimuli. Scoresobtained immediately after and 3 months after the fourthtreatment session were evaluated with the Kruskal–Wallistest with a significance level of 5% ( p¼ 0.05).

Results

A total of 24 patients completed the 3 month study period,which corresponded to 80% of the patients and teeth in-volved in the investigation. Complications such as detri-mental pulpal effects or allergic reactions were not observedduring this period. All teeth remained vital after treatment,with no reported adverse reactions or clinically detectablecomplications.

Table 2 shows the VAS scores (means and standard de-viations) recorded after the application of the stimuli in eachgroup at baseline, immediately after the treatment and3 months after the treatment. No statistically significantdifferences in VAS scores were observed between the threegroups at baseline following the application of any of thestimuli ( p> 0.05). All groups had significant overall reduc-tions in dentinal hypersensitivity in response to air blastand tactile stimulation ( p< 0.05). As presented in Table 2, thethree treatments all resulted in statistically significant re-ductions of VAS scores from baseline, immediately after thelast session ( p< 0.001). Similar reductions were observed3 months after the last session ( p< 0.05). In addition, thelaser treatment tended to result in greater reduction of sen-sitivity between immediate and 3 month results, particularlythe sensitivity as measured by the air blast stimulation( p< 0.05). The effectiveness of the oxalate and placebotreatments measured at 3 months remained at the same levelachieved immediately after treatment ( p> 0.05). However,statistically significant differences were not detected amongthe three groups at both immediate and 3 month results,regardless of the stimulus ( p> 0.05).

The pain severity elicited by the two different stimuliacross all the treatment groups is presented in Table 3. TheVAS scores at baseline demonstrated that the air blast stim-ulus was more effective for detecting sensitivity ( p< 0.05).Three months after treatment, the percent reductions ofsensitivity in response to the tactile and air blast stimuli were65.5% and 62.5%, respectively, compared with baselinescores.

Discussion

Potassium oxalate formulations have become widely ac-cepted for treating dentinal hypersensitivity as many labo-ratory and clinical studies have supported its ability inobliterating dentinal tubules.4,5,23,25–28,30 Scanning electronmicroscopy studies have shown that a topical application ofoxalates on the dentin discs resulted in the precipitation ofinsoluble calcium oxalate crystals on the dentin surface andinside patent tubules.25,30 The crystal deposition reducesfluid movement within dentin and consequently decreasesdentinal sensitivity according to the hydrodynamic princi-ples.5,23,26 A reduction of over 75% in dentin hydraulic con-ductance has been observed after the application of differentpotassium oxalate formulations on dentin discs surfaces inin vitro studies.5,23,26,30 Previous clinical studies on the po-tassium oxalate effects on dentinal hypersensitivity alsosupport the results of the present investigation.4,27 However,an extensive comparison of the results of these studies maybe limited due to the variations in the clinical trial design andexperimental procedures.33,34

Pereira et al.4 obtained a significant clinical reduction insensitivity scores with the application of three different po-tassium oxalate formulations and with the application of aplacebo gel (control group) immediately after, 6 months

Table 2. Means and Standard Deviations of Visual Analogue Scale Scores Recorded at Baseline,

Immediately After, and 3 Months After Application of Each Stimulus

Stimulus Period Laser group Oxalate group Placebo group

Air blast Baseline 6.20� 2.48 A,a 6.41� 2.43 A,a 6.30� 2.44 A,aImmediate 2.66� 3.22 B,a 2.79� 3.48 B,a 2.70� 3.28 B,a

3-month 2.11� 2.69 C,a 2.53� 3.03 B,a 2.46� 2.93 B,aTactile Baseline 3.85� 3.26 D,d 3.67� 3.31 D,d 3.68� 3.29 D,d

Immediate 1.33� 2.54 E,d 1.06� 2.19 E,d 1.25� 2.50 E,d3-month 1.28� 2.19 E,d 1.31� 2.35 E,d 1.29� 2.17 E,d

Different uppercase letters in the same column indicate statistically significant differences for each stimulus ( p< 0.05) and differentlowercase letters in the same row indicate statistically significant differences for each stimulus ( p< 0.05).

Table 3. Visual Analogue Scale Scores (Means

and Standard Deviations) of Sensitivity Elicited

by Tactile and Air Blast Stimuli Irrespective

of the Treatment

Period Air blast stimulus Tactile stimulus

Baseline 6.30� 2.43 A 3.74� 3.27 BImmediate 2.72� 3.31 C (56.8%) 1.21� 2.40 E (67.7%)3 month 2.36� 2.87 D (62.5%) 1.29� 2.22 E (65.5%)

Different uppercase letters indicate statistically significant differ-ences ( p< 0.05). The values in parenthesis represent the percentreductions of sensitivity compared with baseline scores.

CLINICAL EVALUATION OF DESENSITIZING AGENTS 809

after, and 1 year after four treatment sessions at 7 d intervals.In addition to the occluding effects, the neural action of po-tassium oxalate was a potential mechanism for the relief ofdentinal hypersensitivity observed immediately after treat-ment. These authors also used tactile and air blast stimula-tion for eliciting pain sensation. According to Holland et al.,34

these stimuli are recommended for quantifying dentinal painin clinical trials, as they are both physiological and control-lable. Nevertheless, the degree of pain severity was recordedin accordance with a verbal descriptor scale, while in the pres-ent investigation a VAS was adopted. The VAS is consideredan objective method for assessing dentinal pain in whicheach tooth can act as its own control.34 It also offers the ad-vantage of being a continuous scale, and it has been widelyused for assessing the degree of sensitivity in clinical stud-ies.16,17,20,21,27,33,34 In addition, this method is preferableto the use of numerical rating or verbal descriptor scalesas these may be restrictive and not offer enough descrip-tions that could be placed in a continuous order of painseverity.33,34

Pillon et al.27 verified that a single application of a 3%potassium oxalate gel immediately after subgingival scalingand root planing resulted in a greater reduction in dentinalhypersensitivity at 7 (29.4%), 14 (64.6%), and 21 d (81.0%)post-treatment. In contrast, in the present investigation, theeffectiveness of the oxalate treatment observed 3 monthsafter the application sessions tended to remain at the samelevel achieved immediately after treatment. The results ob-tained in the previous study may have been strongly influ-enced by the spontaneous decrease of dentinal pain due toperiodontal procedures. According to Orchardson et al.,1 thesensitivity tends to heal by itself over a period of 3 to 4 weeksafter periodontal treatment. Also, in the investigation de-veloped by Pillon et al.,27 although a VAS had been used forestimating the pain severity, the evaluation of dentinal hy-persensitivity was performed by asking each participantabout pain sensation during routine activities and not inresponse to sensorial stimulation. It has been suggested thatat least two hydrodynamic stimuli should be used for as-sessing dentinal pain in clinical trials and the least severestimulus should be applied first.34 Indeed, when the resultsof the present study were analyzed by type of stimuli whileignoring the treatment groups, more pronounced painfulresponses with the air blast stimulus than with the tactilestimulus were found, and this was also confirmed by Gentileand Greghi.16 This may be attributed to the relatively greaternumber of dentinal tubules that are potentially stimulated byan air blast compared with those stimulated by a probestimulus.21,33 It must also be mentioned that the air blast mayproduce three combined different physical effects: evapora-tion, thermal effect, and physical compression of the air tothe dentinal fluid.

Since lasers emerged as a promising treatment modality,recent studies on dentinal hypersensitivity have begun tofocus on the use of lasers to manage dentinal pain.10,15–20,22,29

This study demonstrated that the GaAlAs low-level lasertherapy reduced the degree of sensitivity in response to hy-drodynamic stimuli immediately after and 3 months aftertreatment. Similar results have been reported in whichGaAlAs laser irradiation provided reductions in dentinalpain elicited by thermal, tactile, and air blast stimula-tion.10,15–17,22 The clinical effect of low-level lasers on den-

tinal hypersensitivity relies upon an immediate analgesiceffect, the result of laser-induced changes in neural trans-mission networks, and a delayed obliteration of dentinaltubules by tertiary dentin, due to increased metabolic activ-ity of odontoblasts.10,15,17,18

Gerschman et al.17 investigated the effectiveness of fourapplications of the GaAlAs laser using the wavelength of830 nm to both the apex and the cervical areas of hypersen-sitive teeth at 1 wk, 2 wk, and 8 wk intervals. It was observedthat the decrease in pain severity became more evident overtime and that at 8 wk, the percent reduction in sensitivity toprobe and air stimuli based on a VAS was 65% and 67%,respectively. These results differ from the findings of Gentileand Greghi.16 They found that with the GaAlAs laser withthe wavelength of 670 nm in six applications with intervalsfrom 48 to 72 h, immediately after the last application, therewere greater reductions in pain in response to tactile stimulithan in response to air blast stimuli. In the present study,laser treatment was performed with the wavelength of660 nm at 7 d intervals, and the pain relief immediately afterthe fourth application was also more pronounced for thesensitivity to tactile than to air blast stimuli. However, thesensitivity to air blast stimulation continued to decline be-tween the immediate and 3 month evaluation, whereas thesensitivity to tactile stimulus remained at a level similar tothat achieved immediately after treatment. Similar to ourstudy, Gerschman et al.17 applied laser irradiation to both theapex and cervical areas of the teeth, while Gentile and Gre-ghi16 applied the laser only to the cervical area of the teeth. Itis claimed that the application of laser beams to the cervicalarea affects A-delta fibers while the irradiation on the apexarea affects C-fibers.17 Although the dentinal pain is said tobe sharp and fast with A-delta fibers whereas the pulpal painis slow and dull with C-fibers, in many cases, the symptomsand etiology are mixed.13,17 In addition, it can be speculatedthat the better result found for the laser group with the airblast stimulus at the 3 month period compared with the re-sult immediately after treatment may have been caused bytertiary dentin formation,10,15,17,18 since such changes are notimmediately detectable. Also, the different results betweenthe air blast and tactile stimuli for the laser group may bepartially explained by the more pronounced painful re-sponse to air blast stimulus compared with the response totactile stimulus, as previously described.

Despite reports of promising outcomes, there is still a needfor clarification regarding the specification of laser irradia-tion parameters for dentinal hypersensitivity treatment asthe tissue response may be different after applications per-formed with different active media, wavelengths, powerdensities, emission modes, or application methods.10,18 Inthis context, Ladalardo et al.10 compared the effectiveness offour applications using 660 nm and 830 nm wavelengthswith the GaAlAs laser in the cervical area of hypersensitiveteeth at 7 d intervals and concluded that the laser applicationwith the 660 nm wavelength was more effective for desen-sitization than the latter.

Although the present investigation demonstrated reduc-tions in sensitivity scores for both the oxalate and the lasergroups, a significant immediate and 3 month reduction wasalso observed for the placebo gel group, and no differencescould be detected among the three groups during the periodof this study. However, in the randomized control studies by

810 VIEIRA ET AL.

Gerschman et al.17 and by Pillon et al.,27 there were signifi-cantly greater reductions in dentinal hypersensitivity in theactive than in the placebo group, and the differences betweenthese groups increased further in the subsequent evaluations.In contrast, Pereira et al.4 and Gentile and Greghi16 foundsimilar results as in our study; they observed no statisticallysignificant differences between the active and control groupsin reducing the pain of hypersensitive teeth. Moreover, pos-itive results with the use of placebos have also been reportedin other clinical trials.4,16,20,32 This may be attributed to theso-called placebo effect. It is described as a complex physi-ological and psychological interaction that depends, to alarge extent, on the relationship between the patient and theprofessional.18,32 In addition, the patient’s response to sen-sorial stimulation is very subjective and largely dependentupon the individual’s pain threshold, and this may influencethe results obtained in clinical trials.2,18,33,34

It is possible that having longer observational periodscould enhance the ability for studies to detect differencesbetween active and placebo groups.

Conclusion

Treatment modalities under study (GaAlAs laser, potas-sium oxalate gel, and placebo gel) provided statisticallysignificant reductions in dentinal hypersensitivity immedi-ately after and 3 months after treatment. Further clinical in-vestigations are needed in order to evaluate the long-termstability of the positive results obtained with these desensi-tizing agents.

Disclosure Statement

No competing financial interests exist.

Acknowledgments

The authors thank Professors Jose Carlos Pereira (Uni-versity of Sao Paulo) and Lidiany Karla Azevedo Rodrigues(Federal University of Ceara) for their important collabora-tion in our work.

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Address correspondence to:Dr. Sergio Lima SantiagoRua Monsenhor Furtado

S=No. CEP 60430-350Fortaleza, CE

Brazil

E-mail: sergiosantiago@yahoo.com

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