Stress Analysis of Abutments with Reduced Periodontal support of RPDs.

随着人口迅速老龄化，涉及牙周受损的修复病例将会增加。在设计牙周损害的远端伸展病例的治疗方案时，对生物力学考虑因素的了解尤为重要。一项关于基牙和支持结构在有各种牙周缺陷的下颌情况下的负荷传递特性的检查被计划进行。本研究的目的是为制定新的局部义齿设计指南提供必要的信息，重点是尽可能长时间地保留基牙。在本研究中，1)通过增加和改进传统的准三维光弹性方法中使用的观察和记录技术来研究复杂情况下的应力分布特征，开发了一种新的应力分析系统；2)建立了光弹性模型来模拟牙齿和支撑结构中的各种条件和应力分析了更多的ES。具体地说，制作了i)单侧远中伸展病例(剩余432个)具有不同垂直和水平吸收(垂直吸收的凹坑和凹槽缺陷，水平吸收率分别为20%和35%)的模型，以及ii)双侧远中伸展情况下第一前磨牙基牙垂直吸收的模型。通过改变载荷(大小和方向)、夹板和固位器条件，对这些模型和正常下颌模型中观察到的彩色条纹图进行了测试。结果表明，在相同的载荷条件下，具有最大骨缺损的模型在最大的区域上产生最大的应力，2)垂直和水平牙周吸收的模型的应力分布模式完全不同，3)两种夹板在重新分配牙周受损的基牙所产生的载荷方面最有效，4)Lbar卡环在减少基牙的整体应力和产生均匀的应力重分布方面最有效。较少

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