title: Finite element analysis of stability and functional stress with implant-supported maxillary obturator prostheses.
abstract: BACKGROUND
  Maxillary resections jeopardize the stability and functional stress generated by implanted-supported prostheses.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the stability and functional stress caused by implanted-supported obturator prostheses in simulated maxillary resections of an edentulous maxilla corresponding to Okay Classes Ib, II, and III, with no surgical reconstruction.
  
  
  METHODS
  Implants were positioned in the residual maxilla, and bar-clip retention systems were designed for each experimental model. The 3-dimensional models of the maxillary resection and corresponding implanted-supported obturator prosthesis, constructed from a computed tomography scan, were used to develop a finite element mesh. Loads were simultaneously applied to the occlusal (80 N) and anterior (35 N) platforms corresponding to the prosthetic teeth. Qualitative analysis was based on the scale of maximum principal stress; values obtained by means of quantitative analysis were expressed in MPa.
  
  
  RESULTS
  The implant-supported obturator prostheses tended to rotate toward the surgical resection, the region with no osseous support. Tensile and compressive stresses in the gingival mucosa and in the cortical bone increased as the osseous support and the numbers of implants and clips diminished.
  
  
  CONCLUSIONS
  All evaluated bar-clip retention systems displayed a tendency toward dislodgment of the obturator prosthesis, increasing as the osseous resection area amplified. The osseous tensile and compressive stresses resulting from the bar-clip retention system for Okay Classes Ib, II, and III maxillectomy may not be favorable to the survival rate of implants.
authors.affiliation: Dentist, Department of Maxillofacial Surgery, Prosthesis and Traumatology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Andréa Alves
authors.initials: AA
authors.lastname: de Sousa
authors.affiliation: Associate Professor, Department of Maxillofacial Surgery, Prosthesis and Traumatology, School of Dentistry, University of São Paulo, São Paulo, Brazil. Electronic address: bscmatto@usp.br.
authors.forename: Beatriz Silva Câmara
authors.initials: BS
authors.lastname: Mattos
mesh_terms: D000539:Alveolar Process / Q000503:physiopathology; D001696:Biomechanical Phenomena; D001732:Bite Force; D003198:Computer Simulation; D017076:Computer-Aided Design; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation; D019094:Dental Prosthesis, Implant-Supported; D005260:Female; D020342:Finite Element Analysis; D005881:Gingiva / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007575:Jaw, Edentulous / Q000503:physiopathology; D008297:Male; D008437:Maxilla / Q000503:physiopathology; D008953:Models, Anatomic; D010158:Palatal Obturators; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods