Minimally invasive endodontics

The primary goal of endodontic therapy is the long-term retention of a functional tooth by preventing or treating apical periodontitis. However, there are many other factors that impact endodontic outcomes such as the quality of the restoration and structural integrity of the tooth after root canal preparation. Contemporary research efforts are currently directed to better understanding dentine behaviour and structure during aging and function. An alternative approach is to minimize structural changes during root canal therapy, which may result in a new strategy that can be labeled 'minimally invasive endodontics'. This paper focuses on describing minimally invasive dentistry in endodontics from a conceptual perspective, relating to diagnosis, access opening, instrumentation and obturation of the root canal system.


INTRODUCTION
Minimal invasive dentistry (MID) can be defined as maximal preservation of healthy dental structures (Ericson, 2007).This is a concept that can embrace all the aspects of the profession.The main goal is tissue preservation, preferably by preventing diseases from occurring and intercepting its progress, but also by removing and replacing it with as little tissue loss as possible.With regards to endodontic procedures, it ranges from diagnosis to making a decision not to treat, to a minimally but purposefully crafted access opening, based on anatomical challenges, to minimal removal of dentin during access opening, enlarging and shaping of root canal to retain as much sound dentin as possible to retention of tooth structure during disassembly and retreatment or considering apical surgical intervention, to perform a crown lengthening procedure to establish sound tooth structure margins for core/crown restorations as opposed to tooth extraction and implant or bridge placement (Murdoch-Kinch and McLean, 2003;Nový and Fuller, 2008).

DIAGNOSIS
Diagnosis of endodontic problems can be a challenging part of treatment process.It can frustrate clinicians and patients.Part of the difficulty is that it is not always a black and white issue; there are many shades of gray including subtle nuances in the patient's history that must be addressed when making treatment decisions (Tables1 and 2).

Access opening
Knowledge of anatomical structures and its variations is essential, so that from caries removal to root canal enlargement, sound tooth structure should be preserved; especially important is the prevention of gouging cervically laterally or into the floor of pulp chamber (Figure 1) (Gutmann, 2013).Endo access has been performed which gives good access to canal orifice, but imagine the thickness of dentin that will remain mesially and distally if a crown was prepared for this tooth (Ericson and Kidd, 2003).The endodontics has been perfectly performed but the tooth is compromised due to excessive loss of tooth structure during access.This is why we keep access limited and you will see sometimes what appears to be incomplete opening of pulp chamber.This is by design and allows important tooth structure to be maintained that contributes to the strength and durability of tooth.
Limiting tooth destruction becomes a greater challenge when attempting to treat teeth with calcified pulp chambers or canals.Assessing the degree of calcification prior to attempting treatment is the key to preventing iatrogenic damage to the teeth.One important aspect of learning to limit the removal of healthy tooth structure for access is that it actually makes endodontic procedures much more difficult (especially in second and third molars) and increases the chances of missing canals, so you need to balance these potential issues with benefits of doing so.Among the objectives of access opening, the point of conservation of tooth structure need to be over emphasized than the other major objectives like, obtaining straight line access, identification of orifices and de-roofing the pulp chamber.

ROOT CANAL INSTRUMENTATION
Even though judicious orifice location and careful canal preparation are essential, efforts should be made to minimize the excess removal of cervical tooth structure in J. Dent.Oral Hyg. the canal orifice through the sequential use and gates glidden burs.A number of literature indicates that the laws of tooth structure cervically weakens the tooth and makes it susceptible to fracture.Even during widening with gates glidden burs, it should not be placed deep into the root canal as this tends to straighten the canal and weaken the canal walls predisposing then to cracks, stripping defects, etc.
The clinician has to carefully decide with which instrument and how wide to shape a given canal to achieve antimicrobial efficiency without weakening tooth structure (Lertchirakaran et al., 1999).
Most NiTi instruments used according to the current guidelines allow wider shapes without major preparation errors and without excessively reducing radicular walls.Remaining dentin thickness was greater than 0.58 mm with GT rotaries, profile and Hero.Earlier studies had indicated considerable thinning of dentin walls after ultrasonic instrumentation, predispose to vertical fracture.So it would seem reasonable to develop better methods of canal cleaning and disinfection that can be used in presence of retained, sound tooth structure.

OBTURATION
Schilder suggested that the ideal root canal obturating material should be well adapted along the entire length of root canal walls and produce a homogenous mass.Currently, with the application of adhesive dentistry in endodontics, the present concept of obturation of root canal is not just the 3-dimensional filling of root canal and accessory canal, but also the reinforcement of root, also known as mono block effect.
Vertical root fractures are complications that are mostly seen in root canal obturated teeth and often lead to extractions.This is mainly due to the force with which the endodontic instrument (plugger, heater, spreader) is applied to the tooth's root canal during the endodontic treatment.
According to (Piskin et al., 2008), the spreader size larger than 25 number causes significant reduction in fracture resistance of roots and another study by Lertchirakarn et al. (1999) which state that fracture can result from excessive lateral condensation forces during root filling (Piskin et al., 2008;White and Eakle, 2000).Only light pressure is required during lateral compaction because the gutta-percha is not compressible and because as little as 1.5 kg of pressure is capable of fracturing the root.The use of strong well placed bonded cone materials and a post (only when necessary) prior to crown placement would help to tie the components of tooth together to resist both functional forces and occlusal leakage.

CONCLUSION
Caution must be exercised when espousing the concepts of MIE in that there are proponents that would have you believe that MIE exists solely with the framework of preserving a few millimeters or less of cervical tooth structure while their empirical claims lack documented and meaningful studies (Clark and Khademi, 2010;Clark et al., 2013).
The long term treatment outcome can be measured visa-vis the extent of invasion.Less invasive procedure generally would seem to provide for a greater degree of predictability.On the other hand, it should be incumbent on each practitioner to know the expected outcome for any procedure, however invasive it may be.

Table 1 .
How the examination results correlate with the diagnosis.

Table 2 .
How the examination results correlate with the periapical diagnosis.
May/May not be sensitive Chronic periradicular periodontitis with symptoms Lesion Sensitive May/May not be sensitive Suppurative periradicular periodontitis Lesion, sinus tract May/May not be sensitive May/May not be sensitive Acute periradicular periodontitis Lesion/No lesion Sensitive Sensitive/Swelling Figure 1.Gouging.