Photo-elastic investigation of influence of dental implant shape and prosthetic materials to patterns of stress distribution.

Occlusal loading has to be considered a key factor influencing bone resorption due to the stress transmitted to surrounding tissues by the implant-abutment structure. The aim of this study was to evaluate, through a photo-elastic investigation, the patterns of tensions distribution of two different implant shapes, which were cylindrical and conical. A 100N load was applied to two implant-abutment structures (with and without a metal-ceramic crown) incorporated in photo-elastic resin. Modification in light refraction were recorded and analyzed through a computerized software. Measurements of stripe extension and position were evaluated. Stress distribution around tapered implant was evaluated to be more uniform than in cylindrical one which demonstrated a high stress concentration at the more cervical region and in the apical region. The presence of a metal-ceramic crown caused an increase in tensions at the implant-resin interface. Conical implants distributed stresses to a larger and well-defined volume of resin and this can cause a decrease of forces acting at the interface. This could be due to the "wedge effect" of this fixture shape which could be considered superior in terms of stress distribution than cylindrical one.