Stress Analysis of Abutments with Reduced Periodontal support of RPDs.

涉及牙周受损牙齿的修复病例将随着人口迅速老龄化而增加。在设计治疗牙周受损的远端延伸病例时，对生物力学因素的理解尤为重要。一项检查载荷传递特性的基台和支持结构的下颌情况与各种牙周缺损计划。本研究的目的是获得重要的信息，以制定新的指导方针的局部义齿设计，重点是尽可能长时间地保留基牙。本研究对传统的准三维光弹性方法中用于检测复杂情况下应力分布特征的观察和记录技术进行了补充和改进，建立了一种新的应力分析系统；建立了光塑性模型，模拟了牙齿和支撑结构的各种情况和应力。具体来说，我们制作了i)单侧远端伸展病例（剩余432例）的各种垂直和水平吸收病例（垂直吸收采用坑状和槽状缺陷，水平吸收率分别为20%和35%）和ii)双侧远端伸展病例（第一前磨牙基牙垂直吸收）的模型。当载荷（数量和方向）、夹板和固位装置条件改变时，这些模型与正常下颌状态模型中观察到的彩色条纹进行了测试。结果表明：1)在相同的载荷条件下，骨缺损最大的模型在最大的区域上产生最大的应力；2)纵向牙周吸收模型的应力分布模式与水平牙周吸收模型的应力分布模式根本不同；3)两种夹板对牙周受损的基牙负荷的再分配最有效。4)在降低基牙总应力和产生均匀应力重分布方面，左卡环效果最好。少

Prosthodontic cases involving periodontally compromised teeth will increase with a rapidly aging population. The need for an understanding of biomechanical considerations is especially great when designing treatment for periodontally compromised distal extension cases. An examination of load transfer characteristics of abutments and supporting structures in mandibular situations with a variety of periodontal defects was planned. The purpose of this study was to attain information vital to developing new guidelines for partial denture designs with an emphasis on preserving the abutment tceth as long as possible.In this study, 1) a new stress-analysis system was developed by adding to and improving on observation and recording techniques used in conventional Quasi-Three Dimensional Photoelastic methods of examining stress distribution characteristics in complex situations, and 2) photoclastic models were made to simulate various condition and stresses in the teeth and supporting structur … More es were analyzed. Specifically, models of i) unilateral distal extension cases (432 remaining) with various vertical and horizontal resorption (crater and trough defects for vertical resorption, and horizontal resorption rates of 20% and 35% were used), as well as ii) bilateral distal extension situations with vertical resorption in the first premolar abutment were fabricated. These models were tested against chromatic fringe patterns observed in models of a normal mandibular situation for their load transfer characteristics as load (quantity and direction), splinting, and retention device conditions were changed.The results showed that, 1) under the same load conditions, the highest stresses over the largest area developed in the model with the largest osseous defect, 2) stress distribution patterns were fundamentally different in models with vertical versus those with horizontal periodontal resorption, 3) two splints were most effective in redistributing loads incurred by periodontally compromised abutment teeth, and 4) the lbar clasp was the most effective in reducing the overall stress at the abutment tooth and producing an uniform stress redistribution. Less