title: Photoelastic stress patterns produced by implant-retained overdentures.
abstract: BACKGROUND
  When 2 implants are used to support a removable overdenture, optimal stress distribution to minimize forces to the implants is desired.
  
  
  OBJECTIVE
  This study used photoelastic analysis to compare the stress patterns generated around implants with 2 retention mechanisms.
  
  
  METHODS
  Two root form implants were anchored in a photoelastic mandible and a removable overdenture was fabricated. The denture was lined with a resilient layer of impression material to simulate oral mucosa. Attachment of the denture to the implants was varied by using ball/O-ring and bar-clip attachments. Vertical and oblique occlusal forces from 10 to 200 lb were applied unilaterally to the right and left first molars. Resultant stress distributions in the photoelastic mandible were photographed and evaluated.
  
  
  RESULTS
  With vertical forces, the ball/O-ring attachment transferred minimal stress to both implants. Vertical forces applied to the bar-clip overdenture created immediate stress patterns of greater magnitude and concentration on both implants. A posterior oblique load resulted in similar stress patterns to both systems with slightly greater stress to the bar-clip overdenture.
  
  
  CONCLUSIONS
  Within the limits of this study, ball/O-ring attachments transferred less stress to implants than the bar-clip attachments when the photoelastic model was subjected to a posterior vertical load.
authors.affiliation: Naval Hospital, Portsmouth, Virginia, USA.
authors.forename: R
authors.initials: R
authors.lastname: Kenney
authors.forename: M W
authors.initials: MW
authors.lastname: Richards
mesh_terms: D001732:Bite Force; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D003799:Dental Stress Analysis / Q000379:methods; D003781:Denture Retention / Q000295:instrumentation; D003828:Denture, Overlay; D003832:Denture, Partial, Removable; D004548:Elasticity; D006801:Humans; D008027:Light; D008334:Mandible; D003765:Models, Dental
chemical_list: D015921:Dental Implants