Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
J Prosthet Dent. 2010 Feb;103(2):91-100. doi: 10.1016/S0022-3913(10)60012-1.
Inadequate dimensioning of the connectors in a cantilever cross-arch fixed dental prosthesis (FDP) in perioprosthetic patients jeopardizes the prognosis of the restoration.
The purpose of this study was to investigate the effect of increasing the vertical dimension (VD) on the maximum stress developed within the connectors during the static loading of a cross-arch FDP extended as a 1- and 2-unit cantilever.
Six digital models were developed, derived from a 3-dimensional (3-D) initial model. In the initial model, the teeth were prepared for metal ceramic restorations and splinted with a cross-arch FDP, extended as a 1- or 2-unit cantilever. The VDs of the connectors proximal to the retaining abutment were 3, 4, or 5 mm. A 3-D finite element analysis (FEA) was performed.
The VD increase, from 3 to 4 mm and from 3 to 5 mm, of the connector distal to the retaining abutment, for each FDP, presented a maximum stress value decrease of approximately 25% and 48%, respectively. The similar VD increase of the connector mesial to the retaining abutment, for each FDP, resulted in relatively smaller stress changes. For the 2-unit cantilever restoration, the stress decreases were approximately 9% and 15%, respectively, whereas in the 1-unit cantilever restoration, the decrease was about 10% for the 4-mm connector. Further increase of the VD to 5 mm did not relieve the peak stress. The highest stress value was measured on the 3-mm connector distal to the retaining abutment in the 2-unit cantilever restoration. Despite the VD increase, the connectors proximal to the retaining abutment still developed the highest stress values of all the connectors for every model.
The connector with the highest risk of failure is the 3-mm connector distal to the retaining abutment of the 2-unit cantilever restoration. Increasing the vertical dimension is beneficial for the connector distal to the retaining abutment, while the resultant stress changes are not substantial for the connectors mesial to the retaining abutment. (J Prosthet Dent 2010;103:91-100).
在牙周病患者的悬臂交叉弓固定义齿（FDP）中，连接器的尺寸不足会危及修复体的预后。
本研究旨在探讨在静态加载悬臂式 FDP 时增加垂直尺寸（VD）对连接体中产生的最大应力的影响，该 FDP 延伸为 1 个和 2 个单位的悬臂。
从三维（3-D）初始模型中开发了 6 个数字模型。在初始模型中，牙齿经过金属陶瓷修复体预备，并与横跨弓 FDP 夹板相连，延伸为 1 个或 2 个单位的悬臂。靠近保留基牙的连接器的 VD 为 3、4 或 5mm。进行了三维有限元分析（FEA）。
每个 FDP 的连接体远端的 VD 从 3mm 增加到 4mm 和 5mm，最大应力值分别降低了约 25%和 48%。每个 FDP 靠近保留基牙的连接器的类似 VD 增加导致相对较小的应力变化。对于 2 个单位的悬臂修复体，应力分别降低约 9%和 15%，而对于 1 个单位的悬臂修复体，4mm 连接器的降低约为 10%。进一步增加 VD 至 5mm 并不能缓解峰值应力。在 2 个单位的悬臂修复体中，最高的应力值是在保留基牙远端的 3mm 连接器上测量的。尽管 VD 增加，但在每个模型中，靠近保留基牙的连接器仍然产生所有连接器中的最高应力值。
在 2 个单位悬臂修复体中，保留基牙远端的 3mm 连接器是最容易发生故障的连接器。增加垂直尺寸有利于保留基牙远端的连接器，而保留基牙近端的连接器的应力变化不大。（J Prosthet Dent 2010;103:91-100）。
