title: Influence of crown-to-implant ratio, retention system, restorative material, and occlusal loading on stress concentrations in single short implants.
abstract: OBJECTIVE
  The aim of this study was to assess the contributions of some prosthetic parameters such as crown-to-implant (C/I) ratio, retention system, restorative material, and occlusal loading on stress concentrations within a single posterior crown supported by a short implant.
  
  
  METHODS
  Computer-aided design software was used to create 32 finite element models of an atrophic posterior partially edentulous mandible with a single external-hexagon implant (5 mm wide x 7 mm long) in the first molar region. Finite element analysis software with a convergence analysis of 5% to mesh refinement was used to evaluate the effects of C/I ratio (1:1; 1.5:1; 2:1, or 2.5:1), prosthetic retention system (cemented or screwed), and restorative material (metal-ceramic or all ceramic). The crowns were loaded with simulated normal or traumatic occlusal forces. The maximum principal stress (stressmax) for cortical and cancellous bone and von Mises stress (stressvM) for the implant and abutment screw were computed and analyzed. The percent contribution of each variable to the stress concentration was calculated from the sum of squares analysis.
  
  
  RESULTS
  Traumatic occlusion and a high C/I ratio increased stress concentrations. The C/I ratio was responsible for 11.45% of the total stress in the cortical bone, whereas occlusal loading contributed 70.92% to the total stress in the implant. The retention system contributed 0.91% of the total stress in the cortical bone. The restorative material was responsible for only 0.09% of the total stress in the cancellous bone.
  
  
  CONCLUSIONS
  Occlusal loading was the most important stress concentration factor in the finite element model of a single posterior crown supported by a short implant.
authors.affiliation: Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas-UNICAMP, Piracicaba, São Paulo, Brazil.
authors.forename: Bruno Salles
authors.initials: BS
authors.lastname: Sotto-Maior
authors.forename: Plinio Mendes
authors.initials: PM
authors.lastname: Senna
authors.forename: Wander Jose
authors.initials: WJ
authors.lastname: da Silva
authors.forename: Eduardo Passos
authors.initials: EP
authors.lastname: Rocha
authors.forename: Altair Antoninha
authors.initials: AA
authors.lastname: Del Bel Cury
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology*; D000704:Analysis of Variance; D003198:Computer Simulation; D017076:Computer-Aided Design; D003442:Crowns; D019250:Dental Implants, Single-Tooth / Q000009:adverse effects; D003769:Dental Occlusion, Traumatic; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000379:methods; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D007576:Jaw, Edentulous, Partially; D008334:Mandible; D016876:Metal Ceramic Alloys; D008963:Molar
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain