Biomechanical Analysis of Implant Assisted-Overdentures with Variations in the Attachments Systems

The aim of this study was to assess the stress patterns on the peri-implant zone and residual alveolar ridge in different overdenture attachment system designs by the photoelasticity method. Four attachments systems were tested: O-ring, ERA, Bar-clip, and Bar-clip/O-ring association. The prostheses were loaded with 100 N in five pre-determined points and the photoelastic model was evaluated by a circular polariscope. The anterior load, O-ring, and ERA showed better stress distribution in relation to the bars systems, which presented stress levels surrounding implants. The molar load, Bar-clip/O-ring association, presented the biggest stress concentration on the periimplant region in relation to the others. When the second molar was loaded, there was a concentration of stress in the alveolar ridge in all situations analyzed. Within the limitation of this “in vitro” study, it could be concluded that there were biomechanical differences among the attachments systems analyzed, principally between isolated and the bars systems. The O-ring showed better stress distribution and the Bar-clip/O-ring showed higher stress concentration.