title: Stress distribution after installation of fixed frameworks with marginal gaps over angled and parallel implants: a photoelastic analysis.
abstract: OBJECTIVE
  The objective of this work was to compare by photoelastic analysis the stress distribution along a fixed framework placed over angled or parallel implants with different gap values between the framework and one of the implants.
  
  
  METHODS
  Two photoelastic models were created: (i) with parallel implants; (ii) with a 30 degrees angled central implant. In both cases, three implants were used, and CP titanium frameworks were constructed with commercial components. A plane polariscope was used to observe the photoelastic fringes generated after initial framework assembly, and also when an axial load of 100 N was applied over the central implant. For both models, stress analysis was conducted on well-fitting frameworks and on another with a 150 microm vertical gap between the framework and the central implant.
  
  
  RESULTS
  The photoelastic analysis indicated that in the model with parallel implants, stress distribution followed the implant axis, and in the model with an angled implant, a higher and nonhomogeneous stress concentration was observed around the apical region of the lateral implants. The placement of an ill-fitting framework resulted in increased preload stress patterns.
  
  
  CONCLUSIONS
  Stresses were generated after screw tightening of the frameworks, increasing when a load was applied and when a vertical gap was present. Angled implants resulted in oblique stress patterns, which were not transferred with homogeneity to the polymeric model.
authors.affiliation: MSc Program, Department of Prosthodontics, University of São Paulo School of Dentistry, Brazil. rmarkari@terra.com.br
authors.forename: Roberto Adrian
authors.initials: RA
authors.lastname: Markarian
authors.forename: Cristiane
authors.initials: C
authors.lastname: Ueda
authors.forename: Claudio Luiz
authors.initials: CL
authors.lastname: Sendyk
authors.forename: Dalva Cruz
authors.initials: DC
authors.lastname: Laganá
authors.forename: Roberto Martins
authors.initials: RM
authors.lastname: Souza
mesh_terms: D019245:Compressive Strength; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported / Q000379:methods*; D003799:Dental Stress Analysis; D004548:Elasticity
chemical_list: D015921:Dental Implants