Influence of prosthesis material on the loading of implants that support a fixed partial prosthesis: in vivo study.

Abstract

Since loading is increasingly believed to be a determining factor in the treatment outcome with oral implants, there is a need to expand the knowledge related to the biomechanics of oral implants and its influencing factors. The aim of this study was to investigate the influence of prosthesis material on the distribution and magnitude of load on oral implants carrying a fixed partial prosthesis by in vivo quantification and qualification of this load. Eight patients with in total nine three-unit fixed partial prostheses on three implants and three patients with in total four two-unit fixed partial prostheses on two implants were selected. Both metal and acrylic resin prostheses were made. Strain gauged abutments were used to measure the load on the supporting implants during controlled load application of 50 N on several positions along the occlusal surface of the prostheses and during maximal biting in maximal occlusion. Additional tests were conducted when the three-unit prostheses were supported only by two implants, thereby creating an extension pontic. A significantly better distribution of bending moments with the metal prostheses in comparison to the acrylic resin prostheses was observed in the case of the three-unit prostheses on two implants. No other difference in load or load distribution with the different prosthesis materials was noted. The clinical significance of the study reveals an increased risk for bending overload of the implants that are closest to the point of load application only in the case of acrylic resin long span prostheses or acrylic resin prostheses with extensions.