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ePaper created 2018-05-16, 11:45:19 | version 1.38.0
Fig. 5a Fig. 5b Fig. 5a The revolution in endo- dontic instrumenta- tion imparted by the first generation of NiTi instru- ments related to their shape memory and super- elasticity. Despite the advantages, these files were susceptible to frac- ture due to fatigue and torsional failure. Fig. 5b Heat treatment (thermal processing) is one of the most fundamental approaches to adjusting the transition tempera- tures of NiTi alloys and affecting the fatigue resistance of NiTi endo- dontic files. Newer alloys (e.g., MaxWire) trans- forming close to body temperature have demon- strated superior resistance to cyclic fatigue and torsional failure. tested.10 MaxWire (Martensite- Austenite electropolish- fleX), while not included in this study, is analogous to Vortex Blue. The temperature effect on the latest gen- eration of NiTi files is shown in Figure 5b. A new generation of adaptive/virtual core files, the XP-endo system (FKG Den- taire) has dramatically changed the view of endo dontic instrumentation. In the absence of a solid core, this system allows the tooth to dictate the canal configura- tion achievable and allows cleaning of the canal with a degree of thoroughness that is unprece dented. Figure 7 details various features of the XP-endo Shaper. The Booster Tip lead section fits into the pre-established glide path, ensuring pre- cise guidance and centering of the instru- ment. A traditional glide path instrument is used consistent with a #15/0.02 (size/ taper) instrument. There are no cutting flutes on the lead section of the Booster Tip, and the XP- endo Shaper instrument slips into the prepared apical component of the glide path to a depth of 0.25 mm. The next 0.25 mm section of the Booster Tip is configured with six cutting flutes. Rotation of these flutes sizes the next 0.25 mm of the canal space anywhere from a #25/0.02 to #60/0.02 (size/taper) instrument; however, the apical size cho- sen for the XP- endo Shaper is #30. The taper of the XP- endo Shaper is 0.01; how- ever, the MaxWire alloy of the Shaper enables the martensitic shape at room temperature to realize the memorized shape as illustrated at body temperature (Fig. 6). By repeated swaths (a motion analogous to whittling in contrast to peck- ing) of the file, the taper created ranges anywhere from 0.02 to 0.08. The ideal intracanal taper throughout is 0.04, which preserves dentinal girth in the coronal third and sustains maximal dentinal reten- tion in any root curvature. Figure 7a demonstrates the difference between the ability of a standard round NiTi file to clear a less than ideal volume of intracanal debris in contrast to the more significant maximal debridement achieved by the XP-endo Shaper’s adaptive discontinuous contact of the canal walls. The desired minimally invasive shape achieved with this unique instrument is shown in Figure 7b. The distinctions of greatest importance between the XP-endo Shaper and conven- tional NiTi instruments are as follows: The Shaper does not compact debris on the flutes, resulting in increased frictional resistance, as it provides substantial space in the lumen or the virtual core; nor does it force the debris apically as evidenced in instruments used with reciprocating motion.11 As the points of contact on the dentinal walls are discontinuous, less stress is applied and thus less cyclic fatigue created than with conventional instru- ments,12 which can be readily demonstrated in photo elastic testing models (Fig. 8a). Figure 8b demonstrates that efforts have been made with other file systems to emulate the uniqueness of the adaptive core design of the XP-endo Shaper; how- ever, regardless of the design alterations, a solid round core remains. Inhibition or eradication of microflora presence from the root canal spaces is a multifactorial conundrum. The bulk of the microbes reside in the primary canal in a planktonic/loose form; however, there is a vast network of labyrinthine irregulari- ties acting as a microbial reservoir that communicate with the primary canal. While irrigation with disinfectants may be very effective against planktonic mi- crobes, it is not sufficiently effective when the microbes are in biofilm form or in ca- nal irregularities. The ability of organisms within the residual biofilms to create an adaptive mechanism to the environmental changes resulting from the treatment protocol can result in recrudescence of the pathosis.13 The biofilm must be elimi- nated before the disinfectants will work. This is analogous to scaling and root plan- ing in periodontal therapy. As already mentioned, most files pro- duce a final round shape on any given canal cross section and as such the prac- 36 — issue 2018 Endodontics Article