Quality Resource Guide l A Guide to Contemporary Endodontic Technology 6th Edition 7 www.metdental.com • TRUShape 3D (Dentsply-Sirona) and XP-Endo Shaper and XP-Endo-Finisher (Brasseler) files These newer files are characterized by having an unusual curve in the design (Figure 5). There are designed so that when they rotate in a canal that has an oval or irregular shape, they provide maximal contact with the canal wall. In theory this should enhance disruption of microbial biofilms, debridement of vital tissues, retreatment and removal of medicaments from the root canal. Preclinical studies have shown some value in this regard, although several recent studies showed that when hypochlorite was used, there was no difference in disinfection compared with traditional files. • EdgeFile, EdgeTaper, EdgeEvolve and EdgeSequel (EdgeEndo) These files are designed to simulate the design and efficacy of other file systems but are offered at lower cost. They are generally comparable in utility and properties to other file systems. Because of the variety of systems available, the dentist is frequently uncertain as to which system he/she should use. Dentists should consider the volume of endodontic therapy in their practice, and whether they are treating moderately difficult cases, such as molars, or only simple cases. For dentists who treat only simple anterior cases with straight large canals, rotary instrumentation will probably not offer them significant advantages. For dentists who perform more challenging cases, they should use systems, which have been evaluated objectively and found to yield reliable results, and not just rely on manufacturers’ claims. The dentist should request from manufacturers literature on objective data, which have been published in refereed journals. Manufacturers usually emphasize the speed of preparation, and the number of instruments needed for completed preparation; however, from a clinical effectiveness perspective this data is usually not useful. Cost is another important factor. Whether the instrument is designed to be used only once should be factored into the cost calculation. It is important to note that most studies on files are preclinical in nature, and the true performance of most of these systems clinically is currently unknown. Reciprocating Files: Reciprocating files follow the principle that the use of watch-winding motion can be extended to allow a motor to engage an instrument with high taper in the canal so that it can incrementally be advanced throughout the entire working length. Thus, one instrument can potentially be used to instrument the root canal, with fewer chances for separation and operation that is more efficient. Two main reciprocating systems are available in the US: WaveOne (Dentsply-Sirona, USA) (Figure 5) and EndoSequence (Brasseler) (Figure 6). When the instrument is activated, it rotates a fraction of a turn (exact amount differs between instruments) in a clockwise direction and then a smaller fraction of a turn counterclockwise. This results in a net advancement of the turn in a clockwise direction. However, the counterclockwise component assures that the instrument does not bind, thus reducing torsional forces etc. Preliminary bench top experiments show these instruments to meet the criteria from a metallurgical and functional perspective. However, treatment outcome studies are not available for them yet. Moreover, a significant limitation of this concept is the lack of apical preparation of the root canal, as discussed previously, and the significant coronal flaring due to the high taper. Therefore, their use is generally decreasing currently. Root Canal Disinfection As noted, there are two distinct diagnostic categories of endodontic pathosis that affect the prognosis: cases with vital (albeit irreversibly inflamed) pulp, and cases with pulp necrosis and a periapical infection. Because of the differences in prognosis for both types of cases, it is important to emphasize more specific disinfection protocols in cases with infections because it has been shown in several studies that better disinfection at the time of root filling results in better treatment outcomes. 4,52,53 Sodium hypochlorite remains the gold standard in root canal irrigation. It is an excellent disinfectant; it dissolves vital and necrotic tissue, and it acts as a lubricant during instrumentation. However, in the root canal environment, there are restrictions in the being able to deliver enough hypochlorite to disrupt microbial biofilms in the entirety of root canal intricacies. Thus, studies have shown that following hypochlorite needle irrigation, about 40-60% of root canals remain with viable bacteria. The use of 17% ethylenediamenetetracetic acid (EDTA), in alternating irrigations with hypochlorite, is now common to remove the smear layer. The smear layer may harbor bacteria and impede the effects of root canal medicaments on bacteria in dentinal tubules. The method of irrigation may make a significant difference in the efficacy of irrigation. Irrigation must be performed with the tip of the needle as deep as Figure 6 A) ProMark Motor (Dentsply-Sirona). B) WaveOne System (Dentsply-Sirona). The instruments are sizes 20/06, 25/08 and 40/08, each intended for use as the single instrument for the tooth/or canal involved. C) ESR Endosequence Reciprocating (Brasseler).