TORQUE IN ROTARY ENDODONTICS

[Drsumitra]

Sattapan et al. (2000a) speculated that fatigue fracture might play a major role in Quantec instruments, but others have reported that cyclic fatigue was a minor factor for ProFile instruments when used correctly and discarded regularly (Yared et al. 2001). Apparently, the instruments’ cross-sectional geometry does play an important role in cyclic fatigue.
However, torsional and flexural fractures are not mutually exclusive categories and cyclic fatigue simulation using metal canals cannot closely resemble clinical conditions because only minimal friction occurs between the rotating instrument and the holding device. Cyclic fatigue might occur differently if instruments are subjected to apically directed force and rotate in curved canals. Clinically, supra-threshold torque does occur for a limited time period only (Peters & Barbakow 2002) and it might be more appropriate to calculate the product of torque and time ) in order to assess the amount of stress the instruments have been subjected to.

        

[sushantpatel_doc]

Anthogyr NiTi Control – Unique Handpiece with torque adjustment

The introduction of the Nickel-Titanium (NiTi) rotary instruments on the market has profoundly changed in the daily practice of endodontics. In deed, the manual stainless steel files, because of their rigidity, are responsible for various mishaps like shifting of the original canal path and perforation.

The NiTi rotary instruments improve the quality of endodontic treatments substantially. Thanks to their flexibility, non-active tip and taper design, they allow regular preparations, while maintaining the natural canal path.

Nevertheless, all experts agree that the main drawback of NiTi instruments, whichever system, is the breakage.

Main Causes of Breakage

* Rotation at too high a speed. Depending on the system used, the rotation speed is generally between 150 and 650rpm. This requires the use of adapted reducing contra-angles or motor-blocks.
* Application of excessive pressure to the files.
* Non-respect of the operating sequences recommended by the manufacturer. Ideally Niti instruments should be used according to the crow-down technique.
* Overuse of the instruments, causing breakage because of fatigue.

Dentsply is proud to introduce the new Anthogyr NiTi Control Contra-Angle, with adjustable torque and automatic declutching.

This contra-angle, manufactured and patented by Anthogyr, is exclusively distributed by Dentsply-Maillefer. It can be used with all NiTi rotary instruments.

Automatic Declutching

A slide ring, located on the contra-angle head, allows the dentist to select from 4 different automatic declutching values. Each of these values, numbered from 1 to 4, correspond to crescent torque values. Value 1 induces a rapid declutching corresponding to a smooth pressure, when the selection of higher values will induce declutching with gradually increasing pressures. Clinically, this means that large instruments (at the beginning of the preparation) will use a higher declutching value (level 4 or 3) while smaller instruments (at the end of the preparation) will use lower declutching values (level 1 or 2). The dentist can easily select the desired declutching value by adjusting the ring on the contra-angle. For added protection, the rotation would stop if excessive pressure is exerted. The instrument can then be removed by simple traction or by reversing the rotation. The dentist may also remove the instrument in the canal manually.

        

[sushantpatel_doc]

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