Load and Stress Distribution Analysis in Implant Supported Partial Restorations

Transfer of excessive loads to implants and their supporting tissue may influence the long-term success of implant supported restorations. Objectives: Analysis of load transfer and stress distribution of implant supported fixed partial dentures. Methods: Four different 3 unit, and two different 4 unit fixed partial dentures, with varying supporting implant number and location were loaded axially 20Kg.Strain gauges mounted at the implant necks, measured stress transmission through the restorations. A photo-elastic model in which the implants were mounted, displayed stress distribution and concentrations, along implant surfaces. Results: The three unit, single crowns, transferred the lowest loads to the implants and the supporting model. The three unit bridge with a central pontic did not transfer more load than three connected adjacent units.The three unit peripherally cantilever bridge transferred the highest horizontal load levels. The two implant supported four unit bridge, with one interposed pontic and one cantilevered pontic transferred less load than a four unit cantilever bridge supported on three adjacent implants (p<0.01, Scheffe Contrasts). Conclusions: This experimental model showed single non-connected crowns transferred the least loads to the implant neck and supporting model. Bridge designs with interposed pontics showed less load transference to the supporting structures than equivalent designs with adjacent implants. The two implants supported three unit cantilevered bridge transferred the highest levels of load transfer of the designs tested.