All-on-4全口速定植牙為近年來對於全口無牙患者一種新興的選擇，其概念為透過四根植體支撐全口的牙科贋復物。本研究目的為透過工程上的全域最佳化方法結合有限元素模擬建立一套自動化牙科力學分析系統，在生物力學的基礎下對於植體的選用及植入方式提出改善建議。
本研究對於不同幾何條件之下顎骨模型分別建立包含下顎骨、植體及贋復物支架的三維有限元素模型，並使用粒子點群法搜尋最佳植體植入參數，包括兩側遠心端植體的傾斜角、長度、直徑及四根植體的植入位置，目標為降低遠心端植體周圍高應變區體積。
結果顯示對於不同下顎骨幾何條件的案例，目標值降低幅度約在60~70%之間，而透過限制條件分析可觀察出在植體植入位置靠近遠心端、傾斜角度較大並選用直徑較大的植體時，可最有效減少高應變區體積。實際案例與驗證實驗結果說明本方法於臨床使用上具可行性與可靠性，可提供在生物力學角度上的最佳植體參數配置，作為治療評估建議。

In recent years, the all-on-4® treatment becomes a new choice for completely edentulous patients, which uses four implants to support the prosthesis of the whole arch. Compared to conventional implant-retained fixed denture supported by six implant or more, the reduced number of implants could cause poor mechanical performance. Improvements should be made to the structural design of all-on-4® to reduce the stress and strain incurred in the jawbone. This study was aimed to develop a numerical approach to search for design improvements of all-on-4® treatment.
Three-dimensional finite element models, consisting of a mandible, implants and prosthesis, were constructed to evaluate the mechanical performance of the prosthesis design. The Particle Swarm Optimization algorithm was implemented to iteratively perform design evaluations using the finite element model and find the optimal solution that minimizes the total volume of the high strain region around distal implants. The design parameters considered were inclined angle, length, diameter and position of implants. The experiment was conducted to validate the result of the optimization.
The results showed that the total volume of the high strain region reduced by 60~70% after optimization. The results suggested the implant position nearer the distal end of framework, larger inclined angle (about 40 degree), longer length and larger diameter. The result of the validation experiment showed that our approach is feasible and reliable in clinical use.

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