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Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
77
Minimally Invasive Endodontics - A Review
*Arbiya Anjum S.1, Swaroop Hegde2 and Sylvia Mathew3
*Corresponding Author E-mail: [email protected]
Contributors:
1 Post Graduate Student, 2Professor
and Head, 3Professor, Department
of Conservative Dentistry and
Endodontics, Faculty of Dental
Sciences, M.S. Ramaiah University
of Applied Sciences, Bangalore -
560054
Abstract
This review compares the various methods of Minimally Invasive Treatment
approaches with Traditional approaches in Endodontics. The MEDLINE, PubMed
databases, bibliographies of all relevant articles and textbooks were searched. As
Devan once quoted “Our goal should be perpetual preservation of what remains
rather than meticulous restoration of what is missing” which is achieved by the shift
of endodontics from extension for prevention to the minimal invasion with the
systematic respect of original tissue. Preserving the integrity of tooth by following
means mentioned in this article one can achieve minimal invasion with maximum
appropriateness. Minimally invasive approach requires in-depth knowledge of Root
Canal Anatomy, Diagnosis and Decision Making, Preservation of Structural
Integrity of Tooth, Alternate Access Designs, Image Guided Endodontic Access,
Dynamically Guided Endodontic Access, Microguided Endodontic Access, Modern
Bur Designs, Cleaning and Shaping, 3D Irrigation and Disinfection, Root
Strengthening and Magnification aids like Loupes and Surgical Operative
Microscope.
Keywords: Minimally Invasive Endodontics, Access Designs, Image Guided
Endodontic Access, Dynamically Guided Endodontic Access, Microguided
Endodontic Access, Loupes and Surgical Operative Microscope
1. INTRODUCTION
With the extensive research, it is seen that it is
virtually impossible to render root canal systems
of teeth bacteria-free. The objective of root canal
treatment is eliminating microorganisms and
pathologic debris from the root canal system and
preventing reinfection1. Dr. Herbert Schielder in
1974, gave the mechanical objectives of cleaning
and shaping which would promote the success of
root canal therapy.
In the quest of eliminating the microorganisms
from the canal system one should also make sure
that there is no extensive loss of tooth structure in
the process. During the endodontic procedures
diagnosis to Treatment Planning involves
minimal invasive approach which includes
correct diagnosis and decision making, minimal
but decisively crafted access openings depending
on anatomical challenges, during access opening
minimal removal of dentin, cleaning and shaping
of the root canal to retain as much sound dentin
as possible, retention of tooth structure,
performing a crown lengthening procedure to
establish sound tooth margins for core/crown
restorations rather than planning a tooth
extraction and implant or bridge placement. The
article here by lists out a few of the approaches of
Minimally Invasive Endodontics (MIE) which
changes the future of dental practice.
2. DIAGNOSIS AND TREATMENT
PLANNING
Usually cases of mature teeth diagnosed with
irreversible pulpitis or apical periodontitis, often
root canal treatment is the treatment of choice to
save the tooth, which lead to loss of dental hard
tissue and subsequently weakening the tooth,
making them more prone to fracture2. With
advancement in research new insights in pulp
biology have developed overtime, a clinical
research on vital pulp therapy now provides
options for enveloping new biologically driven
treatment protocols3.Minimally invasive
endodontics treatment modalities include two
major rewards: firstly, preservation and
maintaining physiological and defensive
functions; secondly, lesser removal of hard tissue
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
78
which preserves structural integrity of tooth.
Thorough knowledge of pulp biology and insight
into why traditional treatment methods leads to
shift in thinking about endodontic treatment.
Possibly avoiding full pulpectomies (complete
removal of the pulp to the apical constriction),
wherever possible .biological response of
immune system could be enhanced by even a
partially retained pulp thus improving the
treatment outcome ,prevents further infection of
the apical area3, and studies have proven that
results of vital pulp treatments are comparable to
conventional root canal treatment5. As stated in
Seltzer & Bender 1963, Garfunkel et al. 1973,
Dummer et al. 1980 Conventional treatment
approaches was thought to have a poor
relationship between the histological state of the
pulp in mature teeth and clinical signs and
symptoms; the recent histological study showed
that there is a good correlation between clinical
symptoms of pulpitis and the histological state of
a diseased pulp6.Irreversible pulpitis cases have
shown the morphological changes indicating the
inflammation or necrosis of coronal pulp while
the radicular pulp being viable. This paves way of
preserving radicular pulp thus preventing need
for a pulpectomy.
This minimally invasive treatment approach
called ‘Endolight’3 helps
1. To preserve immunological functions and
retain the structural integrity of tooth
2. To simplify treatment procedures and to avoid
treatment complications related with varying root
canal anatomy
3. To reduce cost and inconvenience of patients
and society
4. This procedure showed little pain8
The newer proposal for new clinical pulp
diagnosis and related treatment modalities
Initial Pulpitis
Sharp but not lengthy response to the cold test,
not sensitive to percussion with no spontaneous
pain.
Treatment: Indirect Pulp therapy5,9
Mild Pulpitis
Sharp and lengthy reaction to cold, hot and sweet
stimuli that last up to 20s and then subsides,
maybe percussion sensitive. On histology, it
shows limited local inflammation confined to the
coronal pulp.
Treatment: Indirect Pulp therapy5,9
Moderate Pulpitis
Clear symptoms, strong, sharp and prolong
reaction to cold, lasting for minutes, maybe
percussion sensitive and spontaneous dull pain.
On histology, it shows extensive local
inflammation confined to the crown pulp.
Treatment: Coronal pulpotomy10-
partly/completely
Severe Pulpitis
Severe, clear, spontaneous pain reaction to hot
and cold stimuli, regularly, sharp to dull
throbbing pain, very sensitive to touch and
percussion patients’ experiences pain which gets
worse when lying down).
Treatment: pulpectomy11 or tooth extraction.
This treatment strategies are evaluated and
revised in order to maintain the pulp vitality with
minimally invasive approach.
3. STRUCTURAL INTEGRITY OF
TOOTH
Remaining structural integrity of the tooth is
important factor that determines prognosis as it
relates to the post endodontic survival rate of
tooth. Maintenance of strength and stiffness that
resists structural deformation becomes the goal of
all restorative procedures, mainly in endodontics.
A study compared the impact of endodontic
versus restorative procedures on tooth strength2.
They found that endodontic access openings by
themselves have only 5% impact on tooth
stiffness in comparison to any restorative
preparation that removes the tooth’s marginal
ridges which reduces the cuspal stiffness by 63%.
Marginal ridges are a key factor in retaining tooth
strength. Widely held clinical perception is that
endodontically treated teeth are more brittle and
hence more vulnerable to fracture.
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
79
Endodontic treatment major etiologic factor for
tooth fracture, Brittleness of teeth due to loss of
moisture12, insignificant difference in the
moisture content between endodontically treated
teeth and teeth with vital pulp13.
More Emphasis is given on the importance of
conserving the bulk of dentine to maintain the
structural integrity of post-endodontically
restored teeth. The question arises here is why
endodontically treated teeth fail and how to
prevent it?
When endodontically treated teeth fail under
function, that outcome is determined primarily by
2 aetiologies
Those causes stated most simply are:
1) Degree of stress experienced by the tooth
under load
2) Inherent biomechanical properties of the
remaining structure responsible for
resisting fracture.
Attempts made to prevent the fracture rates
are by Preservation of:
a) Peri Cervical Dentin
b) 3D ferrule
c) 3D Soffit
a) Peri Cervical Dentin (PCD)
The dentin surrounding the alveolar crest often
regarded as the “Irreplaceable Critical Most
Zone”. 14 Compromising PCD is not acceptable as
no man-made material can replace the original
tissues.
It is round 4mm above and 4mm below to the
crestal bone. It is insisted to preserve PCD in
order to prevent fracture, preserve the ferrule and
dentinal tubule orifice proximity inside to out.
The survival rate increases with its preservation
proportionately.
Fig. 1 Pericervical Dentin
b) 3D Ferrule
Axial wall of dentin covered by axial wall of
crown. 3D refers to the components of ferrule
namely:
Fig. 2 Ferrule
It has
1. Vertical component - around 1.5 to 2.5 mm14
2. Dentin thickness (Girth) - Absolute minimum
thickness – 1-2 mm14
3. Total occlusal convergence/ Net Taper-Total
draw of 2 opposing axial walls to receive a fixed
crown which is 10° in 3mm of vertical ferrule,
20° in 4mm, possible in the traditional stainless-
steel crowns whereas the newer porcelain crowns
demands 50° or more taper owing to its deep
chamfer marginal zones.14
c) Soffit/Banking
In English literature, the underside of a ceiling, at
the corner of the ceiling and wall is referred to as
soffit but in dentistry it is the stepped access14
which is 360°. Maintain a small border amount of
the chamber roof; near the point where it curves
90° and becomes the wall.
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
80
These 360 soffits - metal ring that stabilizes a
wooden barrel and increased moment of inertia.
In the tooth, this tiny “lip” or “cornice” could be
as small as 0.5 mm, or as large as 3.0 mm in some
cases (where extra strength is needed, or when the
anatomy allows it).
Fig. 3 Dotted line shows the typical cut made to
remove the entire pulp horn. Area between the
lines is referred to as the soffit. 14
Complete Deroofing attempts at removing the
soffit that are far more damaging to the
surrounding PCD. The primary reason to
maintain the soffit is to avoid the collateral
damage that usually occurs, namely the gouging
of the lateral wall. Thus, a more appropriate
access shape is overlaid
Partial deroofing and maintenance of a robust
amount of PCD is demonstrated below:
Fig. 4 A soffit that includes pulp horns on mesial
and distal is depicted
4. ALTERNATE ACCESS DESIGNS
Traditional access designs (TECs) aims at
straight line access into the root canals which
increases biomechanical preparation efficacy and
reduces the procedural errors.
Fig. 5 Traditional access designs (TECs)
With the emphasis on surgical operative
microscope and newer instruments, the New
vision-based mental model is Look, Groom, and
Follow
New instruments are all round-ended tapers.
The rounded ends are to increase the radii of the
gouges and nicks that can act as stress
concentration points. The flat sides help create
smoother, flatter walls and minimize the gouges
and dings that inevitably occur even with the
most careful technique. Small, cone-shaped, low-
speed bur (such as the EG2 [SS White])
Newer access designs include
a) Conservative Endodontic Access Cavity
b) Ninja Endodontic Access Cavity
c) Orifice-Directed Dentin Conservation Access
Cavity
d) Incisal Access
e) Cala Lilly Enamel Preparation
a) Conservative Endodontic Access Cavity
(CECs)
John Khademi and David Clark modified
traditional access cavities and developed the
constricted or conservative endodontic access
cavities to minimize the tooth structure removal
while maintaining the mechanical stability of the
tooth for long-term survival and function of the
endodontically treated teeth. Here, teeth are
accessed at central fossa and extended only as
necessary to detect canal orifices, thus preserves
the pericervical dentin and part of the chamber
floor.
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
81
Fig. 6 CEC in mandibular first molar. The
occlusal view; for comparison purposes, the
outline of TEC is demarcated with a dotted line.
b) Ninja Endodontic Access Cavity (NECs)
An access with a ‘Ninja’ outline, the oblique
projection is towards the central fossa of the root
orifices in an occlusal plane. It is parallel with the
enamel cut of 90⁰ or more to the occlusal plane,
making it easier to trace the root canal orifices
from the varying visual angulations.
c) Orifice-Directed Dentin Conservation
Access Cavity / ‘Truss’ Access Cavity
Purpose of this design is to preserve the dentin ie.
Leaving a truss of dentin between the two cavities
that has been prepared. Separate cavities are
made to approach the canals.15 Mandibular
molars, two separate cavities are made to
approach the mesial and the distal canals where
as in maxillary molars, the mesiobuccal and the
distobuccal cavities is approached in one cavity
and a separate cavity for the palatal canal is made.
Fig. 7 A schematic representation of the (A) TEC
access (black dotted line) and (B) DDC access (red
dotted line) cavity in a mandibular molar
Fig. 8 (A–D) A traditional access cavity (black line
dashed), (A, C, and D) conservative access cavity
(green), and (B–D) ultraconservative ‘‘ninja’’
access cavity (red). Comparison of the 3 access
cavity designs in the (C) occlusal and (D) sagittal
view, respectively. The sagittal view shown as a
conservative access cavity maintains a robust
amount of pericervical dentin. B, buccal; D, distal;
L, lingual; M, mesial
Fig. 9 (A–F) CBCT 3-dimensional reconstructions
and segmentations f lower molars prepared with
different access cavity designs in (A–C) the
sagittal view and (D–F) the axial view at the
occlusal surface. (A and D) A traditional access
cavity (purple), (B and E) conservative access
cavity (green), and (C and F) ultraconservative
‘‘ninja’’ access cavity (red) are segmented on
CBCT reconstructions.
CECs, TECs and NECs and found that TECs
presented lower fracture strength than CECs and
NECs in maxillary and mandibular premolars and
molars and no statistical significance was found
in the fracture resistance mean values of CECs
and NECs16.
CEC was associated with the risk of
compromised canal instrumentation only in the
molar distal canals, it conserved coronal dentin
and conveyed a benefit of increased fracture
resistance in mandibular molars and premolars 17.
TECs may lead to a better preservation of the
original canal anatomy during shaping compared
with CECs, particularly at the apical level18.
Instrumentation efficacy and biomechanical
responses in conservative and traditional
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
82
preparations in maxillary molars and found no
significant difference between the two19. MB2
detection rate of CEC (53.3%) and TEC (60%)
are higher than statistically that of NEC (%31.6).
There was no significant difference between CEC
and TEC in terms of determining MB2 canals20.
No significant difference in the fracture strengths
of teeth prepared using the TEC and CEC
methods, the types of fractures were less serious
with CEC preparation21.
Fracture resistance was higher when accessed
through CEC than TEC. The dentin conservation
afforded an increased resistance to fracture in
CEC group which is doubled the fracture
resistance in TEC group22.Both traditional and
conservative access designs have their own pros
and cons as concentrating on too much
conservative designs can lead to inefficient
cleaning and shaping and also inability to get the
extra canals can in turn lead to failure of the
treatment. Therefore, one must know when to use
based on the right tooth and situation in order to
avoid failures.
d) Incisal Access
Blind Tunnelling: Gouging commonly observed
with round burs which are aggressive in nature
and cingulum access. Buccal-lingual gouging
(not easily seen in x-rays) occurs in nearly every
traditionally-accessed case. 15 Figure 10.
Fig. 10: Blind Tunneling
The Inverse Funnel: As the access grows
internally, an inverse funnel is created. 15 Precious
peri-cervical dentin is lost each time the bur
enters the tooth
Fig. 11: Incisal Access Design
e) Cala Lilly Enamel Preparation
Traditional parallel-sided access compared with
the Cala Lilly enamel preparation. Unfavourable
C factor and poor enamel rod engagement are
typically present when removing old amalgam or
composite restorations or with traditional
endodontic access 900 degree to the occlusal
table. The enamel is cut back at 45 with the Cala
Lilly shape. 15 This modified preparation will now
allow engagement of nearly the entire occlusal
surface
Fig. 12: (a and b) Traditional parallel-sided access
(left), compared with the Cala Lilly enamel
preparation (right). Left - Unfavourable C factor
and poor enamel rod engagement are typically
present when removing old amalgam or composite
restorations or with traditional endodontic access
of 90° to the occlusal table. Right - The enamel is
cut back at 45° with the Cala Lilly shape
5. IMAGE GUIDED ENDODONTIC
ACCESS
It Utilizes image modalities available to
clinicians. Instead of “one size fits all” determine
location and size of access cavity. The objective
is to strategically remove and conserve dentin and
Smallest access cavity possible is made.
Customization of access based on the tooth.
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
83
Fig. 13: Image Guided Endodontic Access
6. DYNAMICALLY GUIDED ACCESS
Dynamic guidance used for dental implants. In
endodontics - first introduced by Dr. Charles M.
It uses information from the patient’s CBCT
volume to plan an access cavity. Overhead
tracking cameras relate the position of the
patient’s jaw and the clinician’s bur in 3-
dimensional space. The clinician, by looking at
the software interface, gets immediate feedback
about the position of the bur as it relates to the
position of the planned access and the tooth
Fig. 14: Dynamically Guided Endodontic Access
7. MICROGUIDED ENDODONTIC
ACCESS
With the help of special software
(coDiagnostixTM, Dental Wings Inc., Montreal,
Canada), alignment with a CBCT and surface
scan allows virtual planning of an ideal access
cavity.23 Subsequently, a template can be
produced by means of a 3D printer. This template
guides a minimally invasive drill to the calcified
root canal.
Fig. 15: Micro guided Endodontic Access
8. MODERN ENDODONTIC BURS
Traditionally used round bur technique relied on
tactile feedback as the round bur drops into pulp
chamber. Round burs are aggressive in nature, the
walls are overextended and gouged in other areas.
Newer burs like ck and endoguide burs has a tip
size less than half as wide as round bur available
from SS White Burs.
Fig. 16: CK and Endoguide Burs
9. CLEANING AND SHAPING OF
CANALS
Negotiating and a complete shaping of canal
being the primary goal. A 3D cleaning and
shaping ensuring minimal mechanical shaping
and a thorough irrigation protocol. Important
things to be included during cleaning and shaping
are: Small apical terminal diameters but wide
tapers apically, while ensuring sufficient dentin
remaining in the body of the root canal.
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
84
Studies vary on which size diameter will
accomplish maximum cleaning. Apical
overpreparation invites fracture of tooth as it
weakens tooth structure.
a. Apical Preparation Geometry: Significant
difference was not found in intracanal
bacterial reduction used with or without
apical enlargement preparation, stating it is
not necessitated to remove excessive dentin
in the apex if sufficient coronal taper is
present which allows enough
irrigation24.Root canal enlargement to sizes
larger than #25 appeared to improve the
performance of syringe irrigation25.The
minimum instrumentation size needed for
penetration of irrigants to the apical third of
the root canal is a #30 file26
b. Self-Adjusting File System: Hollow file -
compressible, thin-walled, pointed cylinder
of 1.5 mm or 2.0 mm diameter and composed
of 120-μm-thick Ni-Ti lattice. File adapts
itself to the three-dimensional canal
morphology both longitudinally and cross-
sectionally. Effectively shapes up to 92% of
the of root canal walls, while allowing for the
continuous flow of fresh NaOCl through the
hollow file by using a peristaltic irrigation
device27
Fig. 17: Self-Adjusting Files
c. Endo-Eze anatomic endodontic
technology: Introduced as a minimally
invasive endodontic preparation system.
Used in a special reciprocating/ oscillating
handpiece for instrumentation of the coronal
part of the root canal about 3 mm short of the
apex. 28 Apical files are hand files with
shortened cutting flutes to cut only in the
apical region of the canal and are used in a
clockwise turn and pull motion
Fig. 18: Endo-Eze Technology
10. 3D DISINFECTION
a. Endoactivator system – In a root canal
system, Endoactivator activates the intracanal
reagents thereby produces a vigorous
hydrodynamic phenomenon utilizing sonic
energy. 29 The flexible vibrating tip which is non
cutting generates an intracanal waves and fluid
activation creating bubbles that oscillate within
the canal, bubbles then expand and become
unstable, then it collapses and implodes. The
implosion creates the shockwaves which
dissipates at 25,000 to 30,000 times/sec.
Fig. 19: Endoactivator
b. Ultrasonic: Acoustic streaming creates
sufficient shear forces to dislodge debris in
instrumented canals. Files activated with
ultrasonic energy acoustic streaming was
sufficient to produce significantly cleaner canals
compared with hand filing alone. The flushing
action of irrigants is enhanced. Improves the
efficacy of irrigation solutions in removing
organic and inorganic debris from root canal
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
85
walls. 29 A much higher velocity and volume of
irrigants flow is created in the canal during
ultrasonic irrigation
c. Photoactivated Disinfection
Photon Induced Photoacoustic Streaming
(PIPS):
Requires any given canal which is prepared upto
size 20 files. Striped and tapered tip of PIPS is
placed still in the pulp chamber alone. Upon
activation of the tip, it creates non-thermal
photoacoustic shockwaves, that travel 3
Dimensionally, also into the complex apical
regions. It eradicates both biofilm and planktonic
contaminates, sterilizing more than 1000 μm
depth into the dentinal tubules.
Fig. 20: Photon Induced Photoacoustic Streaming
(PIPS)
d. GentleWave
It is a multisonic technology with a specific wide
spectrum wavelength with different frequencies.
The reagents flow through the closed system.
With this a 3-dimensional cleaning of canal is
achieved including the complex areas like
isthmuses, lateral canals and dentinal tubules. 30
Collaborative research has shown that this
disinfection method can 3D clean a canal, the
lateral anatomy, and related dentinal tubules.
Fig. 21: GentleWave System
11. ROOT STRENGTHENING
Advancing principle promoting minimally
invasive therapy directs the nominal use of posts
in endodontically treated teeth .Tooth structure is
more valuable than the use of a post in almost
every circumstance where adequate structure
exists for a ferrule.31 Adhesive materials are
minimally invasive.
Posts: Traditional post space preparation resulted
in excessive tooth preparation with the use of
peeso reamers which in turn leads to loss of
structural integrity the newer posts like Ribbond
and Everstick increases the flexibility and
requires minimal tooth preparation. Fibre-
reinforced resin posts are more elastic support to
core.
Fig. 22a. Traditional Post
Fig. 22b. Ribbond Post
Journal of Dental & Oro-facial Research Vol. 15 Issue 02 Aug. 2019 JDOR
86
Fig. 22c. Everstick Post
12. MAGNIFICATION
DH Lawerence quoted “what the eye doesn’t see
the mind doesn’t know, doesn’t exist even if it
does!”. Magnification magnifies the look in
endodontics to the extent that one sees it clearer
which has made possible to look through the
difficulties of root canal treatment. RCT is no
longer a blind procedure with aids like loupes and
surgical microscopes.
Limits of human eye: The resolution of human
eye is 0.2mm. This can be enhanced upto 6
micrometre with the help of Surgical Operative
Microscope. 32
Fig. 23: Loupes
Fig. 24: Surgical Operative Microscope
Surgical microscopes are no longer a luxury but
a necessity in the field of dental practice.
13. CONCLUSION
Minimally invasive endodontics is in the interest
of the patient, and preserving tooth structure
requires optical magnification aids (surgical
microscope), ultrasonic-assisted preparation
techniques, modern file systems, and in-depth
knowledge of the tooth and root canal anatomy.
Focusing on too much of minimal technique my
lead to a higher rate of procedural errors and
benefit may be outweighed by poor clinical
outcome. Hence, the clinician should strike the
right balance between minimal preparation and
traditional endodontic preparation with their own
pros and cons, thus achieving the objectives of
endodontic treatment.
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