臺灣博碩士論文加值系統

下顎第一大臼齒的早期缺失，易造成第二大臼齒向前傾斜(mesio-tipping)是臨床上常見的現象。此種情形在進行口內修復時雖可以先用矯正方法來改正傾斜的牙齒，或使用分離式牙橋體(split pontic)、雙重冠(telescope)、精密附連體(attachment)、鄰接半帽冠(proximal half crown)等設計來製作補綴物。然而這些方法不是耗時費事就是需要較高的經費及技術水準，甚至在製作完成後依然免不了不良的應力傳遞。所以在臨床上，失敗症例是屢見不鮮。在教科書上支台齒的選擇中雖有傾斜超過30度(另說23、25度)的牙齒不宜當作支台齒的建議，回顧文獻卻找不到任何的證據，其源由竟只是學者的看法。因此本研究希望能藉由光彈應力分析來瞭解當下顎第二大臼齒前傾時製作固定補綴物在其行使功能時應力分布的變化情形，並希望能找其傾斜度之臨界點，以提供臨床製作修復物的選擇及參考。
本研究是以類三次元光彈應力分析法，來分析下顎第二大臼齒前傾時，製作固定補綴物在行使功能時應力分布的變化情形。實驗依照下顎第二大臼齒和咬合平面的傾斜度情形(0、10、20、30、40度)製作光彈材料模型，並製作固定牙橋以修復之。於相同的施力條件下，利用光彈組合(polariscope system)以量測特定〝標準點(standard points) 〞其條紋值(fringe order value)之變化量。此變化量乘以各光彈材料模型製作時由圓盤測驗(disk tests)所得之各光彈材料之材料條紋值(material fringe value)可得應力集中指數(stress concentration index)。依此各點之應力集中指數，不同模型間便可進行定量上的比較。
由實驗結果顯示當模型的支台齒從0度增加時，其所得的應力集中指數也相對增加；當支台齒傾斜從0度增加到30度時，其近心側的邊緣齒槽骨所得到的應力集中指數值增加了4倍。且增加到40度時，應力集中指數值有急速增加趨勢。是以當牙齒傾斜的角度超過30度時，於製作補綴物時應做慎重考慮與選擇。

The purpose of this study was to evaluate the stress distributions to the abutments of a fixed partial denture with tilted molar abutments. In cases of the lower first molar being missing, photoelastic models were made with 3-unit fixed partial dentures of which the second molars were tilted 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees mesially towards the occlusal surface. A vertical load of 79.0 Newton was applied distally to the pontic 9mm from the marginal ridge of the second premolar. Quasi-3D photoelastic stress analysis was used, and the stresses were recorded photographically.
The quasi-3D technique of photoelastic stress analysis method was used to evaluate the stress of mandibular posterior fixed partial dentures (FPD) with mandibular second molar mesio-tipping. The points located at 5 mm directly below the root apexes and at 3mm away from the roots were chosen as the "standard points". The "material fringe value" is introduced into the definition of the "stress concentration index" by multiplying the fringe orders. And the fringe orders were counted with a null-balance compensator. Five photoelastic models were compared quantitatively by determining the stress concentration.
From the isochromatic patterns and the Id values, a fourfold increase in stress in the artificial bone at the mesial aspect of the terminal abutment was observed when the load to the long axis was altered from 0 degrees to 30 degrees. The photoelastic models showed that the variation in the stress concentration index also increased directly with inclination, and incrementally increased from 30 degrees to 40 degrees. In the models studied, it should be emphasized that a mandibular posterior fixed partial denture being placed with terminal abutment tilted more than 30 degrees must be critically evaluated.

壹、中文摘要 4
貳、前 言 6
應力分析的理論基礎8
光彈應力分析 12
2 次元光彈性 17
3 次元光彈性 20
參、材料與方法 21
肆、結 果 27
伍、討 論 30
陸、結 論 35
柒、參考文獻 36
捌、英文摘要 44
玖、表 與 圖 46

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