ニッケルチタンファイルで根管形成するためのハンドピースの開発

抄録

Abstract : Many mechanical preparation systems have been developed for greater speed and efficiency of treatment. However, in engine driven mechanical preparation, the operator loses most of his tactile sense, and it is hard to know the exact location of the file tip during the preparation procedures. As a result, precise preparation of the apical portion of the canal has been difficult, and the danger of the destruction of the apical constriction has always been present.

 Recently developed nickel-titanium files have been reported as being safe to use with a rotary motion because of their superelastic property. However, nickel-titanium files seem to be easily broken when they are used with an engine driven rotary motion.

 To avoid these disadvantages of engine-driven preparation and nickel-titanium files, we have developed a new handpiece (the TriAuto ZX, J. Morita MFG. Co., Kyoto) which electronically monitors the location of the file tip and the torque applied to the file during all instrumentation procedures.

 The TriAuto ZX has three automatic mechanisms.

1. Auto-start-stop mechanism

 The file starts to rotate when it is inserted in the canal. Without this mechanism, the operator has to push the main switch to start the rotation for each file change.

 The file stops rotating when it is removed from the canal. This function facilitates changing files and reduces battery consumption.

2. Auto-torque-reverse mechanism

 If there is too much torque, the file reverses its rotation. This mechanism has been developed to reduce file breakage. It also prevents tight locking of the file to the root canal.

3. Auto-apical-reverse mechanism

 When a file tip reaches the immediate vicinity of the apical constriction, the file reverses its rotation. This mechanism has been developed to avoid overinstrumentation.

 Appropriate techniques should be developed to minimize the danger of nickel-titanium file breakage when using our handpiece. Those are ; how to move the handpiece, how to advance a file down the canal, how much force we should load apically, what kind of file sequences (size and taper) we should take, etc.

 Also, it might not be correct to claim that all the instrumentation procedures should be prepared with our handpiece. Simultaneous use of a hand instrumentation depending upon the morphology and the difficulty of the root canal may be a better way to get a good result.