| Summary: | 博士 === 國立臺灣大學 === 機械工程學研究所 === 103 === Ultrasonic bone cutting tips and ultrasonic dental diamond tips give better cutting precision and wound healing than traditional high speed handpieces, but in the other hand, their low cutting efficiency is not competitive to the traditional high speed ones, which becomes a hurdle for dentists to use during operation. The purpose of this study is to improve the cutting efficiency of ultrasonic bone cutting tips and dental diamond tips.
This study started from two directions to increase the cutting efficiency. Firstly, the parametric construction of 3D model and Finite element method (FEM) were used for analyzing amplitude and stress of the cutting tip structure, combining with SolidWorks Simulation as tools to find out the optimized design of the outlook structure of ultrasonic bone cutting tips and ultrasonic dental diamond tips. Secondly, the design of cutting blade of bone cutting tips was based on cutting theorys, the parallel blades of the traditional orthogonal cutting tips were changed to inclined ones that made inclination angle to the moving direction for the oblique cutting effect. Two blades front and rear were crossover to form a tip with “Z”-like multiple blades on one end (Z-type model). In addition, the cutting blade was inclined to make top bevel angle, front and rear blades with different height of apex also crossed to increase cutting depth.
The experimental result of the optimized outlook structure design showed that the material removal rate (MRR) of modified cutting tips was 19% higher than the foreign brand Satelec. The MRR of the best design Z-type model was compared to orthogonal cutting blade of local brand Bonart and cone-shape cutting blade of foreign brand Satelec, which represented significantly higher bone cutting surgery efficiency by 107% and 44%. However, in combination of optimized outlook structure design and the Z-type cutting blades showed increments in 146% and 72% respectively, when compared with local brand Bonart and foreign brand Satelec. These results showed significant improvement on bone cutting efficiency of ultrasonic cutting tips.
Besides，it was found in the currently common dental diamond tips with single-size diamond grains that the roots of nickel layer of diamond grains would lean against the enamel surface when grinding depth reached the roots of the tip, which declined grinding efficiency. In order to improve such problem in the design of dental diamond tips, three grains size mixed diamonds were used to plate on tip surfaces with finer diamond grains full-filled the voids among the coarser diamond grains. This design reduced exposure of nickel plating layer of dental tip as well as insufficient grinding.
The experimental results showed that MRR of diamond tips was 5% higher than the foreign brand Satelec after the outlook structure design was optimized. The MRR of three-size mixed diamond grains tip was 225% higher than the foreign brand Satelec with single-size diamond grains. However, in combination of optimized outlook design and diamond grains design, three-size mixed diamond grains tip had better MRR than foreign brand Satelec single-size diamond grains tip with 243% increment. The new designs significantly improved the MRR of enamel grinding of ultrasonic diamond tips.
As a conclusive result of this study, it showed advance of outlook structure optimization and cutting blade/diamond grains design on cutting efficiency, but the improving levels depended on the design of original instruments.
|
|---|
