| Summary: | 碩士 === 臺北醫學大學 === 牙醫學系碩博士班 === 97 === Nickel-Titanium (Ni-Ti) instruments have become widely used in the endodontic treatment. However, their unexpected separation was a serious concern in endodontics. To date, no scientific methods have been developed to evaluate the functional lifespan of Ni-Ti instruments. In this study, we used resonance frequency (RF) analysis to nondestructively detect the fatigue life of Ni-Ti instruments to determine the feasibility of this technique for use in the clinic.
Recently, a new manufacturing method to produce more flexible and resistant Ni-Ti instruments (Twisted File, TF) has been developed. It uses twisting of a ground blank in combination with heat treatment to reportedly enhance superelasticity and increase cyclic fatigue resistance. With this regard, this research aim to investigate the influence of Ni-Ti instruments with different manufacturing methods on the cyclic fatigue. In addition, the relationship between the fatigue life and RF value was evaluated by comparing the lifespan of Ni-Ti instruments and their measured RF values.
To simulated clinical operation, we used a commercialized RF analysis device (Implomate). Our result shows that the average RF value of new ProFile instruments focus between 5050+0 Hz and 5563+25 Hz. After the in vitro simulated operation, the RF values of the ProFile instruments decreased gradually. For ProFile instruments, without unwinding defects, normalized RF value (K value) before fracture is 0.95+0.01. However, when unwinding defects were detected in the ProFile instruments, the normalized RF value (K value) before fracture decreased to 0.90+0.01. On the other hand, the RF value of the new Twisted File (TF) instruments was measured from 5150+0 Hz to 5250+0 Hz. After clinical operated procedure was simulated, all the instruments showed fracture with unwinding defects. The K value before fracture of the TF instruments was 0.93+0.02.
These results demonstrate that the RF analysis tests have potential as a tool for structural detection in Ni-Ti instruments and that the method presented is feasible for clinical application.
|
|---|
