| Summary: | 碩士 === 中原大學 === 醫學工程研究所 === 93 === Due to the restriction of material and complex canal geometry, the traditional Endodontic instruments are susceptible to complications such as: ledges, zipping, transportation and perforation. These are incidences that should be avoided in clinical practice. With the advancement of material technology, Nickel-titanium (Ni-Ti) instruments are two to three times more flexible than stainless steel instruments. Ni-Ti endodontic instruments were introduced to facilitate the instrumentation of curved canals. The flexibility is an important property that allows preparation of curved canals while minimizing unfavorable side effects. This research is aimed to compare the mechanical behaviors of different geometries of endodontic Ni-Ti rotary instruments by using finite element analysis. The analysis results can be used to predict likely failure locations and to provide suggestions for product designs. The research was divided into several parts. Starting from reproducing the same analysis used in previous literatures, then to incorporate the special material property of Ni-Ti into the finite element analysis. Afterwards, four different rotary instruments with total working length were analyzed. The stress distributions of the instruments under different loading and boundary conditions were compared. The results showed that ProTaper has higher peak stress value under pure bending loading. There was no obvious difference in stress distribution for torsion loading. The Ni-Ti material curve used in the analysis can represent the unique super-elastic behavior. Moreover, combining bending and rotation loading condition can provide useful information for instrument under cyclic tensile and compressive stresses which can cause fatigue failure. Finally, artificial resin root canals were created to simulate the instrument through different canal shapes. Through this simulation, the normal contact force and stress in canal surface and the pivoting points within the instrument and canal were found and compared.
|
|---|
