下顎後牙區贋復體的連結與否於不同皮質骨厚度及植體傾斜角度之應力分析─三維有限元素分析法

研究背景和目的: 近年來的研究顯示，植體的成功率受到非常多因素交互的影響，其中非垂直軸向的力量為植體失敗的原因之一，因此臨床上常需要利用角度型支台齒來改善角度不佳的植體以及製作贋復體。根據之前研究結果發現不同角度型支台齒的連結與否對於植體周圍骨內應力有顯著性的差異，但下顎骨皮質骨厚度的差異是否對不同角度支台齒連結或不連結有何影響，尚無明確結論。本研究的目的主要在探討下顎後牙區不同厚度之皮質骨，對於不同植體傾斜角度和贋復體的連結與否其應力分布的影響情況。材料和方法: 本實驗目的是利用三維有限元素法來模擬下顎骨第一與第二大臼齒缺牙區，皮質骨厚度分別為0.5mm、1.0mm、 2.0mm等三種，分別植入不同傾斜(0∘、15∘、30∘)角度的植體，共計6組角度。贋復體的設計則分為連結固定與不連結固定，並於贋復體上個別施予垂直力(F1平行植體長軸方向)及斜向力(F2頰側往舌側與植體長軸交角45∘)於第一及第二大臼齒中心咬窩處各200N；共計400N，來觀察植體、支台齒與植體周圍齒槽骨的應力分布情形。本實驗利用變異數分析(ANOVA)將所得應力值進行統計分析，藉由分析結果討論施力方向、皮質骨厚度、植體傾斜角度、贋復體連結與不連結等各項變因對應力分布所造成的影響。結論: 結果顯示，施力方向、皮質骨厚度、植體傾斜角度、贋復體連結與不連結等上述變因對植體與植體周圍齒槽骨的應力值有統計學上顯著性的差異(p<0.05)。其中施力方向和植體傾斜角度為最大影響因素，接下來皮質骨厚度；最後為贋復體的連結與否，對於應力值分布有顯著的影響卻是四種影響變因中最少的。總結: 由統計結果得知影響植體和支台齒應力的四種變因中，施力方向占了絕大因素，主要是植體受到非軸向力時所產生的側方力矩使應力值會遽增，因此控制施力方向才是減少植體周圍應力集中的有效方式。植體的角度是影響皮質骨表面最大壓縮應力最顯著的因素，當植體傾斜之角度增加時應力值會有增加的趨勢，強調了植體植入的方向角度，應儘量和咬合面垂直來避免產生側方力矩對於骨頭癒合產生的破壞。而皮質骨厚度佔了第三重要的因素，皮質骨厚度的增加對於植體周圍應力有顯著的減少現象，所以更顯示出植牙區條件評估的重要性。至於贋復體的連結或不連結情況，對於應力值分布有顯著的影響卻是四種影響變因中最少的，但是在植牙區皮質骨厚度條件不佳的病人，贋復體為連結固定形式對於應力分布有利於周圍應力的減少，同時必須和病人強調口腔清潔的重要。本實驗著重在植體的生物力學方面之理論，希望藉著本次實驗的結果使臨床醫師決定治療計畫時能做更多方面的整體考量，未來能有更多相關的臨床研究，提供更完善的實證數據，建立臨床醫師正確思維與治療準則。關鍵字: 贋復體連結固定、角度型支台齒、植體傾斜角度、皮質骨厚度、有限元素、應力分析

關鍵字

贋復體連結固定；角度型支台齒；植體傾斜角度；皮質骨厚度；有限元素；應力分析

並列摘要

Background and purpose: In recent years the study of success rate has revealed that the success rate of dental implant is affect by many factors.And non-axial loading is one of main factor for implant faliue.Sometimes the dentist need angled abutments for the improvement of path insertion and prothetic fabrication.According to the precious study,statistcally difference between angled abutment with prosthesis either splint or not.Otherwise there is no general consensus on influence of angle abutment either prosthesis splint or not in various cortical bone thickness.The purpose of this study is ascertain the effect of stress value on difference cortical bone thickness over lower posterior mandible among various angled abutment splint or without splint. Materials and methods: A 3-D model for finite element analysis was constructed lower posterior mandible which containing three different cortical bone thickness(0.5mm、1.0mm、2.0mm) and six different implant inclinations(0∘、15∘、30∘) with two designs of prosthesis(splinted or non-splinted).A simulate load(200N)was applied on each centrl fossa of first molar and second molar with vertical(F1) and oblique(F2) forces,total force was 400N.The stress value between implant and peripheral cortical bone is addressed to be the primary issue in this paper.Analysis of variance(ANOVA)were used to detect significant difference among loading type,cortical bone thickness,implant inclination,splint situation. Results: The ANOVA indicate a significant effect for stress value between implant and peripheral cortical bone among loading type,cortical bone thickness,implant inclination,splint situation.Loading type was the main effect for stress distribution over implant and peripheral cortical bone,followed by implant inclination,cortical bone thickness,and splint situation. Conclusion: Loading type was the main effect for stress distribution. While there is non-axial force on implant,the bending movement was increased significantly. The result indicated the best position for implant is prepandicular to occlusal plane.The stress value decrease when cortical bone thickness increase,and increase when implant inclination increase. Evalution for bone quality of implant side before sugery become important.The influence of splinted or non-splinted crowns was less compare with other three main factors.Although splint or non-splinted crowns had less effect on stress distribution,poor bone quality of implant site still need splint prosthesis favorable for stress distribution .And patient should need oral hygiene well control.While this study has its biomechanical limitations,it is hopes that it can serve as basis for treatment plan.In future,more clinical research need provide more reliable evidence-base data for clinical workers. Keywords: splinted crowns,implant inclination,cortical bone thickness, finite element method,stress analysis