Automated endodontic instruments. Online class on the characteristics of rotary and reciprocating instruments.
Automated endodontic instruments part of the endodontic instruments class.
in: Costa & Satos. Torsional strength of two nickel-titanium rotary endodontic instruments. Pesq Odont Bras, v. 14, n. 2, p. 165-168, abr./jun. 2000.
Introduction Aiming to achieve a continuous taper that follows the original shape of the root canal and to reduce possible accidents during instrumentation, many studies have been conducted on the manufacturing of endodontic instruments with significant changes related mainly to the type of metal used in their manufacture.
Recent advances in technology have presented endodontic instruments produced from nickel-titanium alloys that present advantageous properties in relation to stainless steel alloys, such as: greater resistance to fracture by clockwise or counterclockwise torsion and greater modulus of elasticity, which allows the return to the original shape after deformation, besides the high flexibility. This new generation of endodontic instruments took WALLIA et al.10 (1988) to initiate studies with nickel-titanium endodontic files, observing through scanning electron microscopy, that file #15 of nickel-titanium presented superior resistance to torsion fracture when compared with file #15 of stainless steel manufactured by the same process.
Seeking to increase the resistance to torsion of endodontic instruments SANTOS6 (1994) determined a recrystallizing thermal treatment that reduces the original hardening of the file, relieving the induced tensions and improving the final quality of the instrument, making it safer, and the nickel-titanium files still present a higher resistance to torsion when compared to conventional files submitted to the recrystallizing treatment. CAMPS; PERTOT2 (1994); SERENE et al.7 (1995), ROWAN et al.5 (1996), WOLCOTT; HIMEL11 (1997) were in agreement when they evaluated the resistance to torsion between stainless steel and nickel-titanium files, observing that both reached or exceeded the specifications of ANSI/ADA nº 281 (1989), specially the nickel-titanium instruments for having mechanical properties that encourage other evaluations with clinical and laboratorial studies.
Nickel-titanium hand files do not have much cutting efficiency, because their high flexibility does not allow the file to stick to the canal walls, thus promoting little wear, but the metallurgical properties of strength and elasticity of nickel-titanium used in appropriate conditions and with convenient anatomical designs made possible the manufacture of rotatory endodontic instruments, making cleaning and shaping of the root canal faster and more efficient. Research presented by several authors as PINEDA; KUTLER4 (1997), TEPEL et al.8 (1997) and THOMPSON; DUMMER9 (1998) have shown that rotary systems are promising when compared to manual instruments. The resistance to torsion of the various endodontic instruments is related to their manufacturing and forming process.
Nickel-titanium files and rotary systems are manufactured by machining since their mechanical properties do not allow torsion. As for their shape, the manual nickel-titanium files show a similar design to the conventional ones, while the rotatory systems basically show a triangular cross-section, positive angle slightly more aggressive as the Pow-R instrument, or they can show a U-shaped design, helix angle, slightly positive cut in both working surfaces and active tip (SC) or inactive tip (LX) with angle almost 0 degree that does not make thread as the Quantec Series 2000 system. The variation in design of nickel-titanium instruments manufactured for use in engines can determine very different clinical behaviors due to the mechanical properties determined by the various shapes, which makes it important to study these differences and their consequences.
Automated endodontic instruments
