Analysis of strain at selected bone sites of a cantilevered implant-supported prosthesis.

Cantilever length of the superstructure of an implant-supported prosthesis can be affected by the location, number, and dimensions of the implants, arch form, opposing dentition, and functionally generated forces. In this study, the effects of cantilever length on load distribution to implants was analyzed. A fresh bovine rib was used to create a clinical simulation in which three implants were used to support an implant prosthesis. The implants were connected by means of a cantilevered superstructure. Six linear strain gauges were placed in strategic locations where it has been reported that stress is concentrated. The model was loaded with an Instron machine and the load was applied at 0, 5, 10, 15, 20 and 25 mm along the cantilever length. Each loading test was repeated five times, and loads of 10 and 20 pounds were applied. Dynamic registration of the strain was recorded at each gauge. Significant differences in the magnitude of strain between the six strain gauge locations were recorded with the 10 and 20 lb loads and at all cantilevered lengths. The results revealed that the greatest maximum strain occurred at the strain gauge positioned on cortical bone over the apex of the most distal implant under both loading conditions.