Moscow, Russia
21 or 22 november 2020
Cracks and fractures in vital
and endodontically treated teeth

Professor Zvi Metzger
Prof. Zvi Metzger
Former Dean and former head of Department of Endodontology at the Tel-Aviv University School of Dental Medicine. Presided over the National Association of Endodontics and served as the Chairman of the Israeli Endodontic Society. He was a visiting fellow at the National Institute of Dental Research (NIH) in Maryland, USA, and as a visiting professor at the University of North Caroline, Chapel Hill, USA Today serves in the editorial board of the Journal of Endodontics. He is known for his R&D works in design of innovative endodontic instruments.
Topic 1. "Cracks and fractures in vital and endodontically treated teeth"

Part 1.Cracks in the crown of vital teeth: An evasive painful entity

Crack in a vital molars or premolar is commonly an evasive, yet painful entity. The patient suffers for a long time from pain on mastication that prevents him from chewing on the affected side.Nevertheless, the dentist may not find any radiographic signs and all the teeth on the affected side are vital. This condition may last for few months and the patient often has seen several dentists who have also found nothing. A diagnostic procedure will be presented and discussed, with the aim of making everyone in the audience an expert in early diagnosis of such condition. Diagnosis must be madebefore the tooth/crown fractures and the "mystery" solved. Treatment options will be discussed, all with the aim of preventing the final catastrophic fracture of the tooth/crown.

Time frame: 45 min.

Part 2. Early vs. delayed diagnosis of vertical root Fractures (VRFs)

Vertical root fractures (VRFs) are often undiagnosed or misdiagnosed for a rather long time, thus frustrating both the patient and his dentist. Early stage VRFs cannot be detected with periapical radiographs. The "typical radiographic appearance of VRF", which is commonly mentioned in papers and quoted in textbooks, often represents unjustified failure to diagnose the VRF in time, before a major damage to the surrounding bone has occurred. The most pathognomonic early sign of VRF is a unique type of periodontal pocket, which is very narrow and deep, which may appear with or without a sinus tract that is located more coronally than expected from a sinus tract emerging from a periapical lesion, even at the attached gingiva. CBCT cannot usually demonstrate the early VRF per se, however it may be very useful to identify the pattern of bone destruction that occurs along the VRF. The aim of this presentation will be to make each of the audience an expert in early diagnosis of VRFs.

Time frame: 45 min.

Part 3. The biomechanics of vertical root fractures

To minimize the risk of VRFs it is essential to understand the biomechanics of VRFs and the predisposing factors that may lead to such fractures. Some of these are naturally occurring factors, such as the shape of the root and pre-existing naturally occurring micro-cracks. Nevertheless, other predisposing factors are iatrogenic in nature and are result of the endodontic procedure that was carried out on this tooth. These include excessive instrumentation of the canal, instrumentation that results in uneven thickness of the remaining canal walls, type of spreader used for lateral compaction and above all the creation of iatrogenic micro-cracks by using large taper rotary and reciprocating files. The predisposing factors will be reviewed in details, including suggesting ways how to minimize or avoid the iatrogenic contribution to the creation of VRFs.

Time frame: 45 min.

Topic 2. "The endodontic frontier: Challenges in endodontic treatment"

Part 1. The challenge of shaping and cleaning of oval canals and curved canals

Root canal instrumentation with rotary or reciprocating NiTi "files" is a common practice in endodontics. Both these types of instruments are actually machining devices (not files), which cut the radicular dentin to form aenlarged canal with their own shape. When applied in straight narrow canals, effective shaping and cleaning may be achieved, as the entire canal wall is included within the machined space. Nevertheless, when applied in oval canals rotary or reciprocating "files" fail to touch the canal walls in the buccal and/or lingual recesses of the canals. Studies with microCT have also demonstrated that in curved canals about 50% of the canal wall is also untouched by these instruments. The rotary and reciprocating "files" have also a tendency to straighten curved or S-shaped canals, thus damaging the root by removal of sound dentin in unnecessary places. In addition to their inability to effectively clean oval canals, both rotary and reciprocating "files" have a tendency to actively pack the un-instrumented recesses with debris, which later cannot be removed from the rcesses, even with passive ultrasonic irrigation. Most companies have recognized these drawbacks and are attempting to produce new instruments with out-of-the-box design. The first of these instruments was the Self-adjusting file (SAF) but it most likely to be followed by other innovative designs such as the XP-Endo and a whole array of other instruments yet to come.

Time frame: 45 min.

Part 2. The challenge of effective irrigation and effective disinfection of oval canals

The critical role of effective irrigation in both cleaning and disinfection of root canals has long been established. In narrow and straight root canals, which were machined by either rotary or reciprocating "files", syringe and needle irrigation may be an effective way to clean and disinfect the canal. Nevertheless, such method leaves much to be desired in oval canals as well as in curved ones. The concept stating that "the file shapes; the irrigant cleans" represents wishful thinking rather than the reality in oval canals. It is based on the wrong belief about the "magic ability" of sodium hypochlorite to dissolve tissue and debris that were untouched or packed into recesses by the action of rotating and specially reciprocating files. More effective irrigation tools have been designed, such as passive ultrasonic irrigation and Endovac, but they have severe limitations when curved canals are concerned. More effective tools have recently been designed to provide a more effective irrigation and cleaning of both oval and curved canals, the first of which are the Self-adjusting File and the XP Endo finisher. Other devices are likely to follow. The effective irrigation by the new devices has been shown to substantially affect the disinfection of oval infected root canals.

Time frame: 45 min.

Part 3. The challenge of micro-crack and fracture formation in the root dentin

Mechanized instrumentation of root canals with NiTi rotary or reciprocating "files" has greatly improved both efficiency and safety of root canal treatment. Nevertheless, there is a "price ticket" attached to this efficiency. Most of the instruments in these groups cause micro-cracks in an alarming percentage of the treated roots. Such micro-cracks may be a predisposing factor for future vertical root fractures. The response of the profession to these findings may be divided into 3 groups: (a) ignoring the issue or denial of its importance, (b) research aimed to undermine the vast data generated in many laboratories, which demonstrated the generation of micro-cracks and (c) development of instruments that do not cause excessive stress in the radicular dentin. The studies related to this phenomenon will be critically reviewed and discussed.

Time frame: 45 min.

Part 4. The challenge of obturation of oval canals

In recent yearsthe concept of obturation of root canals,using a master cone that has the size and taper of the last NiTi rotary file that was used in the canal, has been widely promoted. While in some cases this method may be effective, it may lead to failure in many other cases in which the canal cannot be adequately cleaned using rotary or reciprocating files and irrigation. The first challenge of obturation of oval canals is to adequately clean all tissue and debris from the canal and its recesses. Only then comes the issue of how to adequately obturate the clean oval canal. The use of various obturation methods will be discussed, with emphasis on (a) the use of customized master cones, which have the 3D shape of a given individual canal and (b) the use of bioceramic sealers.

Time frame: 45 min
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