Effect of severely reduced bone support on the stress field developed within the connectors of three types of cross-arch XXXX .

@entity2300 @entity1 @entity7607
STATEMENT OF PROBLEM: Increased technical failure has been reported for cross-arch @entity2300 ( @entity2300 ), particularly for cantilever units with minimum osseous support. PURPOSE: The purpose of this study was to investigate the effect of severely reduced bone support on the stress field developed within the connectors for 3 types of cross-arch @entity2300 . MATERIAL AND METHODS: Six digital parametric models were developed, derived from a 3-dimensional (3-D) initial model. The latter simulated a @entity1 mandible, dentate bilaterally to second premolars, with normal height of alveolar bone. In the initial model, the teeth were prepared and splinted with a cross-arch @entity7607 bilaterally with one of the following: no cantilever, 1-unit cantilever, or 2-unit cantilever. All structures were obtained from computed tomography (CT)-scan images or constructed in 3-D computer-aided design (CAD) and reverse engineering environments. A 3-D finite element analysis (3-D FEA) was performed. RESULTS: The reduction of the alveolar bone in the no-cantilever @entity7607 model caused a greater increase of stress in the region of connectors among the splinted teeth in comparison to the 1- and 2-unit cantilever @entity7607 model. The stress state within the connectors of the cantilever segment remained constant. The connectors proximal to the retaining abutment demonstrated the highest stress values, independent of the osseous support. The stress values in the region of the same connectors in the 2-unit cantilever restoration were almost double, compared to the 1-unit cantilever model. Decreasing the osseous level in the 1- and 2-unit cantilever @entity7607 models caused milder stress distribution and magnitude in the region of connectors among the splinted teeth. CONCLUSIONS: The stress field developed within the connectors of the cantilever segment is independent of the osseous level. The stress field within the connectors among splinted teeth depends on the osseous support and both the presence and length of the cantilever segment. Furthermore, this study indicates that adding a cantilever segment has a positive effect on the stress behavior of the splinted teeth connectors in situations of reduced osseous support.
