title: Effect of severely reduced bone support on the stress field developed within the connectors of three types of cross-arch fixed partial dentures.
abstract: BACKGROUND
  Increased technical failure has been reported for cross-arch fixed partial dentures (FPDs), particularly for cantilever units with minimum osseous support.
  
  
  OBJECTIVE
  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 FPDs.
  
  
  METHODS
  Six digital parametric models were developed, derived from a 3-dimensional (3-D) initial model. The latter simulated a human 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 FPD 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 FPD 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 FPD 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 FPD 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.
authors.affiliation: Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Marianthi
authors.initials: M
authors.lastname: Manda
authors.forename: Christos
authors.initials: C
authors.lastname: Galanis
authors.forename: Vasilis
authors.initials: V
authors.lastname: Georgiopoulos
authors.forename: Christofer
authors.initials: C
authors.lastname: Provatidis
authors.forename: Petros
authors.initials: P
authors.lastname: Koidis
mesh_terms: D016301:Alveolar Bone Loss / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D017076:Computer-Aided Design; D000044:Dental Abutments; D003799:Dental Stress Analysis / Q000379:methods; D003779:Denture Design; D003830:Denture, Partial, Fixed; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D008334:Mandible / Q000000981:diagnostic imaging; D008954:Models, Biological; D011859:Radiography