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The primary goal of endodontics is to clean organic remnants from the root canal system, and shape it to receive a three dimensional hermetic (fluid- tight seal) filling of the entire root canal space. To achieve this, a combination of chemical and mechanical components are used with the ultimate goal of eliminating bacteria from the root canal system. Advances in many fields of science have contributed to the development of new or improved materials and their delivery, as well as new or improved instruments for use in endodontics. These include irrigation, imaging, instruments, MTA, apex locators, magnification and ultrasonics.
Within traditional endodontic thought, it is considered that files shape and irrigants clean.1 This implies that there are areas that cannot be instrumented within the root canal system and this has been clearly identified in studies.2 The use of irrigants during endodontics is essential to compliment instrumentation to enhance debris removal and reduce viable microbes within the canal systems.3 It has been shown that after chemo-mechanical preparation of root canal systems using rotary instruments, 5.25% sodium hypochlorite, rinsed with EDTA and obturated with GP and zinc oxide eugenol cement, residual infection remains.4 Attempts have been made to improve irrigation of the canal systems. Conventional irrigation techniques utilize a needle and syringe to deliver the irrigant into the canal under positive pressure. If too much pressure is applied or the needle wedges into the canal, extrusion of the irrigant into the periapical space could occur causing significant patient morbidity. To reduce this one method introduced, uses negative pressure irrigation rather than conventional positive pressure irrigation ââ‚¬" EndoVac (Discus Dental). The Endovac system introduces a microcannula down the canal to working length, irrigation is added to the pulp chamber and sucked down the canal by the holes in the end of the microcannula. This system has shown to cause less extrusion of irrigant and less postoperative pain than needle irrigation.5 An additional method to improve irrigation is the use of agitation. The introduction of subsonic agitation, EndoActivator (Advanced Endodontics), agitates the irrigant solution within the canal. Use of the EndoActivator for 30 seconds with sodium hypochlorite has been shown to be more effective in removal of debris and reduction of microbes. 6,7
Imaging in endodontics is required during diagnosis , treatment planning, during and after endodontic procedures. Traditional imaging in endodontics utilises plain film 2-dimensional (2D) imaging to evaluate a 3-dimensional (3D) object. The image produced is a combination of superimposed shadows of varying shades between black and white.8 The introduction of digital image receptors that have the same or better resolution than plain film brings several advantages during endodontics; lower radiation dose, no chemical processing, easier storage and image transfer, quicker image acquisition, and enlarged images enable better communication with the patient.9 However, the digital image is still a 2D representation of a 3D object. For endodontics the recent availability of Cone Beam Computed Tomography (CBCT) images has allowed clinicians to evaluate the third dimension. CBCT has been designed to image the maxillofacial skeleton and the radiation dose is similar to conventional extra-oral radiography.10 Multiple 2D images are recorded and stitched together via computer software to provide an imaging viewing system that can be manipulated in all three axies. CBCT increases the ability to detect apical periodontitis, assessment of root canal anatomy such as the presence of mesobuccal 2 in the maxillary first molars, vertical root fractures, and internal and external resorptive lesions.11 The 3D images are valuable in planning apical surgery,and the use of CBCT is valuable in diagnosis and assessment during the endodontic treatment process.10
Mechanical removal of bacteria from the root canal system and appropriate shaping, requires the use of small diameter instruments with a cutting edge. An ideal endodontic instrument would not cause a perforation, transportation, break or create a ledge and would preserve the original shape of the canal to working length.11 This instrument is not currently available. Initially, carbon steal was used in the manufacture of root canal instruments but were prone to corrosion.13 Stainless steel hand files were an improvement though stiff and tending to straighten curved root canals.14 The development of nickel titanium (NiTi) rotary files has revolutionized canal preparation. NiTi rotary instruments enable predicable shaped canals in a short time period due to the strength and flexibility of the nickel-titanium alloy base files.12 The benefits of NiTi rotary instrument use include reduced patient and operator fatigue, increased speed of preparation and less files required to obtain consistent shaping of the canals.14 There is also less aberrations of the canal and less transportation in curved canals. 15
Mineral trioxide aggregate (MTA) is a well researched material that is being used successfully in many endodontic operations. MTA is becoming the treatment of choice for perforations during endodontics, pulp capping and in pulpotomy procedures.16 In comparison to calcium hydroxide, MTA is superior in preserving pulp vitality after direct pulp capping. 17 It has been shown that MTA has greater biocompatability, and contributes to dentin bridge formation and tissue repair during pulp capping procedures when compared to calcium hydroxide.18
Perforations during endodontics or post hole preparation have been difficult to repair, as there has been no material suited for this procedure. Materials used include amalgam, glass ionomer cement, composite resin, zinc oxide eugenol cement, calcium hydroxide, gutta-percha, IRM, and SuperEBA but their inability to seal the communication between the oral cavity and the underlying tissues, or their lack of biocompatability result in unpredictable outcomes.19 MTA has excellent sealing properties and promotes healing with more predicable results in repairing perforations in comparison to other materials.19 The use of MTA is limited by its setting time of 3-4 hours, as it is susceptible to leaching during this time.
Traditionally the working length (WL) of root canals has been determined by radiography. However, the radiographic apex does not correspond with the apical foramen in many teeth. Mizutani et al21 reported that the coincidence of the root apex and apical foramen was 16.7% of central incisors and cuspids and in 6.7% of the lateral incisors. The time taken for a well positioned radiograph with intra-canal instruments to determine WL is time consuming and largely unnecessary with the current accuracy of EAL technology. Using today's EAL's, it takes less time to determine WL ,shape the canal and place a master cone than to obtain an accurate WL radiograph.12 It has been shown that the accuracy of EAL is superior to radiographic determined WL.20 The preference of some endodontist is to determine WL with an EAL, complete canal preparation and confirm WL with the master apical cone in-situ using a conventional periapical radiograph. 12 The development of electronic apex locators (EAL) has changed the practice of endodontic treatment for the better, enabling increased accuracy and speed of the procedure.
A human can distinguish 2 points as being separate if they are about 0.2 mm apart. Endodontists routinely perform procedures requiring
resolution well beyond the .2 mm limit of human sight.
Incisions, furcation and perforation repair, root canal
location, and caries removal are a few procedures that
have tolerances well beyond the .2 mm limit. 22 Loupes provide fixed magnification up to about 12 times and operating microscopes from the region of 3 times to 30 times. With the range of magnification provided by operating microscopes, procedures that are enhanced include diagnosis
, non surgical endodontics,
surgical endodontics, marketing
, documentation and patient education
.23 Enhanced vision provided by magnification had assisted in the location of canals, and in the direct visualization of vertical root fractures. As stated by Arnold 24 , 'the use of the operating microscope results in improved diagnostic and therapeutic accuracy and considerably expands treatment options.' Surgical endodontics has benefited greatly with the use of operating microscopes, enabling the increased visualisation of the apex and enhanced use of microsurgical instruments and materials to provide a predictable apical seal. 25 The incorporation of magnification in endodontic procedures has improved patient care and treatment outcomes.
Since the introduction of ultrasonics into endodontics by Richman26 in 1957, the use of ultrasonic devices during endodontics has expanded to be incorporated into most aspects of endodontics. Unlike rotary burs, ultrasonic tips do not rotate. Piezoelectric ultrasonic tips vibrate at 40 Hz in a piston like motion, whilst magnetostrictive ultrasonic tips vibrate in a figure eight motion at 24 Hz.27 Due to this action, ultrasonic hand pieces offer incomparable enhanced safety and control, especially when near furcations or achieving conservative cavity preparations. Visibililty during conventional and microscope aided endodontics , relative to conventional handpiece use, is enhanced due to the slender tip design.28 Numerous ultrasonic tip designs have been developed for use during endodontics. These vary in length and width as well as the material that they are made of. For instance, the tips used in cavity preparation should be diamond-coated or zirconium
nitride coated. These tips provided efficient cutting at the point and along the edge of the tip.28 Ultrasonic use during access cavity preparation assists in removal of dentine bridges and uncovering calcified canals. 29 Removal of posts is greatly enhanced by the use of ultrasonics. The ultrasonic tip is applied to the top of the post and operated at maximum power with irrigation to vibrate the post and break up the cement enabling post removal.30 Broken instruments with in the root canal can be a challenge to retrieve. Ultrasonic tips that are slender, long are used to make a void around the top of the instrument and then to vibrate it, loosening the instrument enabling retrieval.30 Special tips are used during root end preparation during periradicular surgery overcoming problems during conventional preparations such as unnecessary bone removal for instrument access and bevelling of the tip.31 Buchanan 29 is so impressed with ultrasonics that he stated that ââ‚¬Å“Any clinician who does molar endo without ultrasonics is working too hard, is experiencing more anxiety
than is necessary, and is most likely not finding MB2
canals in more than 40% of their upper molar cases (50-60% is a minimal expectation since they are present 70% of the time).ââ‚¬Â