超音波骨刀及牙鑽之切削效率提升研究

Improvement of Cutting Efficiency of Ultrasonic Bone Cutting Tips and Dental Diamond Tips

林廷章(Ting-Chang Lin)

指導教授 ： 廖運炫

國立臺灣大學/工學院/機械工程學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.02357

摘要

超音波骨刀(Ultrasonic bone cutting tips)及牙鑽(Dental diamond tips)比較傳統高速手機(High speed handpiece)有較好的切削精度及傷口癒合，但是它的的切削效率遠低於高速手機，造成醫師使用上的障礙。本研究的目的為超音波骨刀及牙鑽之切削效率提升研究。
從結構與刀頭兩方面進行切削效率的提升，首先在結構上用參數化建構3D模型及有限元素法分析刀具結構的振幅及應力，結合SolidWorks Simulation 最佳化設計的方法，設計超音波骨刀及牙鑽的較佳之外形結構。其次，在超音波骨刀前端刀頭的設計，依據切削理論，將傳統超音波骨刀的正交切刃改變成傾斜，使其與垂直運動方向夾一傾斜角(Inclination angle)，達到斜交切削的效果，並將前後兩刃相互交錯，形成一端視如Z字形的多刃骨刀(Z-type齒型)。除此之外，切刃與水平面傾斜一齒頂斜角(Top bevel angle)，前後齒高低交錯，以加深切刃切削深度。
實驗結果顯示，外形結構經最佳化後，骨刀比國外廠牌Satelec，切削效率提升約19%。而在刀頭設計方面，Z-type齒型的斜交切削刀刃之材料移除率，相較於國內品牌百捷正交切削的刀刃及國外廠牌Satelec尖形的刀刃，切削效率各別提升約107%及44%。若結合較佳的骨刀結構外形與Z-type齒型的骨刀, 其材料移除率比較國內品牌百捷骨刀及國外廠牌Satelec骨刀，各別增加約146%及72%，大幅提升超音波骨刀切骨手術的效率。
此外，在超音波牙鑽頭的設計方面，發現目前單顆粒度鑽石之牙鑽，在磨削深度達牙鑽根部時，會有鑽石根部鍍鎳層頂住牙釉質表面，使得磨削效率下降的問題。因此採用三種粒度鑽石混合電鍍牙鑽頭表面，以較細的鑽石顆粒填補較粗鑽石顆粒之間的空隙，減少牙鑽頭鍍鎳層的裸露，減少鍍鎳層的無效磨削。
牙鑽於磨削牙釉質的實驗結果顯示，外形結構經最佳化後，牙鑽比國外廠牌Satelec，切削效率提升約5%。三種粒度牙鑽比較國外廠牌Satelec牙鑽的材料移除率，約提升225%。若結合外形結構與三種粒度鑽石混合的牙鑽，比較單粒度鑽石的國外廠牌Satelec牙鑽之材料移除率，約提升243%，明顯提升了超音波牙鑽磨削牙釉質的材料移除率。
本研究結果顯示, 外形結構最佳化與刀頭的設計對於切削效率確實達到很好的效果，但是提升多寡會因原始刀具設計的好壞，而有不一樣的提升效率。

關鍵字

高速手機 ； 超音波骨刀 ； 超音波牙鑽 ； 齒頂斜角 ； 牙釉質 ； 材料移除率

並列摘要

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.

並列關鍵字

high speed handpieces ； ultrasonic bone cutting tip ； dental diamond tip ； inclination angle ； wedge angle ； rake angle ； material removal rate

參考文獻

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