Force Sensor Design and File Mechanics Analysis for Endodontic Treatment
|關鍵字:||力感測器;力學分析;根管治療;有限元素法;Force Sensor;Mechanics Analysis;Endodontic Treatment;Finite element method|
Endodontics is a branch of dental therapy, commonly known as root canal treatment. Endodontic files play an important role in the process of endodontic therapy, the mechanics analysis of file is necessary. In treatment, a NiTi file enters the curved root canal, and the higher rigidity of NiTi instrument can not only avoid unnecessary deformation, but also improve the efficiency of debridement. And the stress distribution of endodontic instruments can be used to predict file failures. To assist endodontic therapy, in this study, a force sensor has been designed and fabricated for measuring the axial force and the bending moment simultaneously. By detecting the bending moment, one can know the severity of bending. Axial force detection is also desired, since excessive axial forces may result in file buckling or even root canal perforation. Therefore, this study can be divided into two main parts, which include (1) mechanics analysis of endodontic instruments (2) design of a force sensor. First, we investigate the nonlinear deformation of files under bending load. Analytical results are derived by using Euler-Bernoulli nonlinear differential equations that took into account screw pitch variation of NiTi instruments. The maximum curvature of the instrument is found in this study to occur near the instrument tip. Second, torsional results are derived by using the elasticity theory that take into account triangular cross-sections and tapered shapes of NiTi instruments. This study discovered that the maximum stress occurs near the instrument tip and the middle side of a triangular cross-section. The analysis based on the analytical model and the finite element nonlinear analyses are carried out. The proposed analytical models are validated by numerical results in analyzing NiTi instruments. Third, this study uses a piezoresistive material as a force sensing material, because it can sense loads directly and the size can be miniaturized. The force range that the force sensor can measure meets dentists’ needs. The force types that can be measured include the normal force and bending force. Each sensing cell consists of a pressure-sensitive electric conductive rubber and an electrode. Experimental results on hysteresis, repeatability, and nonlinearity are presented to validate the proposed sensor.
|Appears in Collections:||Thesis|