不同螺紋與齒槽骨間隙對牙科植體影響之有限元素分析

Abstract

此研究利用數值模擬的方法，找出植體與齒槽骨間隙變化時之應力以及應變的分佈狀態，尋求對人工植牙最好骨整合環境的情況。 數值模擬時，利用有限元素中的軸對稱模型，模擬四種不同螺紋及三種不同間隙狀態之組合。四種不同螺紋分別為公制螺紋、惠氏螺紋、角螺紋及鋸齒螺紋。三種不同間隙狀態為植體與齒槽骨無間隙、植體與齒槽骨有間隙及植體與齒槽骨完美骨整合。模擬中，將施以一垂直的平均咬合力20MPa，摩擦係數則設為0.3，並且利用石膏和純鈦植體，模擬前述螺紋與齒槽骨間隙之組合作為比對之實驗。 模擬結果顯示角螺紋之植體有最大之應力集中，且其有最多的骨萎縮區域及較高的疲勞破壞區域；鋸齒螺紋之植體有最多之應力集中區域，及最多的疲勞破壞區域；同為三角螺紋的公制螺紋與惠氏螺紋在結果上並無顯著之差別，但惠氏螺紋在植體與齒槽骨有間隙的情況下，植體有最小的應力集中，而齒槽骨有最多的骨成長區域。 以對骨整合的影響來看，公制螺紋與惠氏螺紋較角螺紋以及鋸齒螺紋有較佳的骨整合環境。惠氏螺紋在植體與齒槽骨有間隙的情況，在完美骨整合前有最佳骨整合環境，在完美骨整合後植體有較小應力集中。植體有著最小的應力集中，齒槽骨有最多的骨成長區域，可以使骨整合時間較為縮短。

The purpose of this study was to investigate the stress and the stain distribution around implants and alveolar bones and to determine the best thread form and misfit of implants and alveolar bones which promote osseointergration. An axial symmetric finite element models were adopted for simulate four implant threads, the thread forms of ISO thread, whitworth thread, square thread, and buttress thread. Three misfits between implants and alveolar bones were considered. The conditions of implant with no misfit in alveolar bones, implant with misfit in alveolar bones, and implant with perfect osseointergration in alveolar bones. Each implants was applied with a pressure of 20 MPa in vertical direction. The static friction coefficient between implant and alveolar bones was selected 0.3. Experiments with dental stone as the alveolar bone and Ti implant were carried out to verify the finite element analysis results. Base on the simulate results, square thread has maximum stress and the highest disuse window and higher pathologic overload zone. Buttress thread has maximum stress areas and the highest pathologic overload zone. There is no discernible difference between ISO thread and whitworth thread. But whitworth thread has lowest maximum stress and highest mild overload zone at the condition of implant with misfit in alveolar bones. It is found that ISO thread and whitworth thread are better in terms of promoting osseointergration. The best condition for osteointergration is whitworth thread implant with misfit in alveolar bones.