Photoelastic analysis: prosthesis-retained cemented/screwed with different implant geometric configurations

Objectives: The aim of this research was to assess the biomechanical behavior of single implant supported dentures with different retention systems and implant geometric configurations.

Methods: Six photoelastic models were made and divided into 2 groups. Group 1: MA = external hexagon screwed prosthesis-retained, MB= internal hexagon screwed prosthesis-retained e, and MC= screwed cone-morse prosthesis-retained; Group 2: MD= external hexagon cemented prosthesis-retained, ME= internal hexagon cemented prosthesis-retained and MF= cemented cone-morse prosthesis-retained. The implants used were Conexão Master Screw ( São Paulo-Brazil ) measuring 4.00x10.00 mm and the single dentures were standardized and made of Ni-Cr alloy. A circular polariscope was used, and axial loads of 100N applied. The results were photographed with a Nikon D80 camera and assessed in the graphic program Photoshop 7.0 (Adobe System) for qualitative analysis.

Results: The models with screwed prosthesis-retained obtained a very similar stress distribution pattern, however, the external hexagon model presented greater stress intensity around the implant screws, demonstrating the worse situation. Models with cemented prosthesis-retained generally presented less concentrated and less intense stress distribution. The internal hexagon and cone morse implants presented similar stresses irrespective of the type of connection.

Conclusion: Implants connected with cemented prosthesis-retained showed more favorable stress distribution and the external hexagon implant presented the worst stress distribution with the highest intensity.