全人工顳顎關節在臨床使用上已經有超過六十年的歷史，臨床統計資料顯示進行全人工顳顎關節的術後恢復程度都相當良好，療效高達75%以上。臨床報告指出全人工顳顎關節的失敗原因主要是發炎、植體斷裂與骨釘鬆脫為主。目前討論全人工顳顎關節的文獻，大多討論發炎反應為主，對於植體斷裂與骨釘鬆脫的相關研究甚少。本研究的目的為評估不同的骨釘數量與位置因素，對於病患植入全人工顳顎關節的生物力學影響進行探討。
三維有限元素模型包括顳顎關節窩、下顎骨、兩種全人工顳顎關節(Christensen TMJ implant、Techmedica TMJ implant)、韌帶、肌肉與骨釘，依臨床手術規劃術後模型，並針對骨釘鎖入不同數目(四至六根)與位置(六種不同配置)搭配出36種組合模型，以探討骨釘對於全人工顳顎關節之生物力學影響，並進一步探討全人工顳顎關節之應力、應變及位移與植體斷裂及骨釘鬆脫的關聯性。
結果發現分散骨釘的固定方式可以提供較佳的應力分佈，且鎖入最上方的骨釘越靠近顳顎關節，鎖入最下方的骨釘越靠近下顎角的固定效果最為顯著。骨釘數目增加證實可以改善生物力學表現與降低局部應力集中，但是釘固定在正確的位置比增加骨釘數目的影響更為明顯。本研究中的兩種植體在生物力學行為表現之下可以明顯看出Techmedica TMJ implant比Christensen TMJ implant好，而且使用鈦合金的Techmedica TMJ implant不管在哪一種固定方式其植體的最大等效應力皆小於材料的降伏應力，這也表示在臨床上使用Techmedica TMJ implant確實可以獲得較好的成功率。

Total temporomandibular joint (TMJ) prosthesis has been used for over 60 years from clinical reports, TMJ functions could be improved at least by 75% after performed reconstructive surgery. Previous clinical statistics indicated that major failure modes of the total TMJ prosthesis included inflammatory, implant fracture and screw loosening. Contrast to inflammatory issue, only few literatures were executed to investigate the implant fracture and screw loosening. Therefore, the purpose of this study was to investigate the biomechanical effect of the total TMJ prostheses with various combinations in screw numbers and configuration.
Based on surgical guidance of TMJ reconstruction, three-dimensional finite element models consisted of temporal fossa, mandibular condyle, two types of total TMJ prosthesis (Christensen and Techmedica brand), ligaments, muscles and bone screws where established. There were arranged with various screw numbers (four to six) and screw configuration (six patterns). In total 36 combinations of the TMJ finite element models were build.
The results shown that the most important factor in screw configuration is the location of the first screw which is required to be as high as possible, near the joint location. Secondly, screws should be applied as spread as possible. Using these two principles would significantly reduce the peak von_Mises stress on all components, such as the screws, bone around screw holes and mandibular component. Also, the simulation outcomes shown that the configuration, location, of the screw is more important than the number of screw. It is necessary to apply more screws only when the screw can not be applied on the upper region of the bone.
Based on the peak von_Mises stress, the Techmedica TMJ, using Titanium, is better than the Christensen TMJ, using Cr-Co-Mo alloy, due to its higher yield stress as well as lower peak von_Mises stress on the implant. This observation is consistent with clinical outcomes which indicated that Techmedica TMJ has a higher success rate.

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