利用三維有限元素法測定下顎後牙區不同植體螺紋間距的咬合應力分析

研究目的：近年來牙科植體的應用越來越趨於頻繁。關於牙科植體之贗復物的問題也受到相當的重視。由於牙科植體常使用於咬合力較大的後牙區, 下顎後牙區的贗復物在承受功能的咬合力量所造成的力矩常常是影響植體壽命的重要因素。因此如何使其植入後有高的成功率,一直是牙科醫師與相關學者努力的方向。臨床上許多研究報告指出，失敗的植體多半在植體頸部有明顯的骨質流失。動物及臨床實驗報告中顯示骨頭的喪失和植體不當的受力有關。不當的受力會使得過度的應力集中在植體周圍的骨頭上，進而造成骨頭的吸收。研究方法：進行不同螺紋間距與螺紋外型之人工植牙的基本力學探討是本研究的主要目的。本實驗設計植體的螺紋有兩種：三角形(triangular type)和梯形(trapezoid type)，螺紋間距設定為0.8、1.2、1.6mm ，共計五種模型。模型依實體外型由切片、外形掃瞄組合，來建構出合理的三維有限元素分析模型。針對不同之咬合力方向進行不同螺紋間距與螺紋外型的後牙植體生物力學分析，以瞭解咬合力對植入結構體可能產生的影響與破壞。透過分析後所得到之下顎骨的應力分布狀況與其他學者所提出之骨整合流失理論相互配合比較，探討對植入失敗的機制。結果：不論在那一個方向的受力，應力皆集中在植體頸部與緻密骨交接的螺紋上。在側方受力時，所產生的應力值，皆比垂直受力來得大。在三角形螺紋植體中，以1.2mm螺紋間距的植體有較低的應力值。在梯形螺紋植體中，以1.6mm螺紋間距的植體其應力值較低。結論：不管在接受垂直或是側方力量，植體以及骨頭間應力分布皆集中在緻密骨以及植體交接的地方。在相同螺紋間距下，梯形螺紋比三角形螺紋較能降低受力所產生的應力值。在0.8mm螺紋間距的模型中，垂直受力時產生的應力分布值大致和其他模型相同，但一旦接受側方力量時，其產生相當大的應力值，臨床上在選取植體種植時應審慎考慮植體之螺紋間距與形態。

關鍵字

牙科植體設計；有限元素分析；下顎臼齒區；應力值

並列摘要

In recent the applications of dental implants are becoming more and more prevalent. The problems related to the prosthesis of dental implants, therefore, had been noted because dental implants are more in the posterior area in which there were always loaded with high occlusion forces. The success of dental implants mainly depends on how much forces in the prosthesis can endure. Dentists and scholars had been working to obtain a high success rate of dental implants, since it was introduced. Clinical studies have been reported that the significant bone loss around the implant neck of failing implants was found and various hypotheses have been proposed to explain this bone reaction. Animal experiments and clinical studies have shown that bone loss around implants may lead to implant failure, which was associated in many cases with unfavorable loading conditions. Inappropriate loading will cause excessive stress in the bone around the implant and may result in bone resorption. The main goal of this research is to investigate the effects of stress distribution of the fundamental biomechanics of different implants with vary screw types and screw pitches. Two different types of screw threads was used : triangular -thread and trapezoid -thread. Both threads have screw pitches of 0.8, 1.2, and 1.6mm, totaling five different experimental models. Three-dimensional anatomic models were constructed by finite element method with contour scanning and cross section slicing. Stress distribution is concentrated at the neck of implant where the first thread of implant contact with cortex bone. When the directions of load are form buccal and lingual side, the compressive stress of alveolar bone and von Mises stress of implant are higher than vertical loading. In triangular screw type implant, stress increases with the screw pitch. And in trapezoid screw type implant, stress increases with the decreasing of screw pitch. By analyzing the stress distributions, it was induced by different directions of occlusion forces, we can investigate the effects of occlusions, which distribute on the different implant structure and also study the stress which distribute in mandible with different implant structure will be analyzed with osseointegration theory.

並列關鍵字

implant design ； finite element method ； mandibular molar ； stress analysis

參考文獻

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利用三維有限元素法測定下顎後牙區不同植體螺紋間距的咬合應力分析

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