Cyclic loading of implant-supported prostheses: comparison of gaps at the prosthetic-abutment interface when cycled abutments are replaced with as-manufactured abutments

STATEMENT OF PROBLEM: Implant-supported prostheses are mechanically connected to implants. When this connection is a screw joint, it is likely that the fit will be imperfect. Previous studies demonstrate that deformation can occur at the interface between the prosthesis and implant following cyclic loading. This deformation alters the fit of components. If implant connection components, abutments, were to be reoriented or replaced, it is likely that deformed surfaces would no longer approximate each other. Likewise, it is possible that the deformation may deleteriously alter the fit to replacement components. PURPOSE: This study evaluated the changes in prosthesis-implant abutment fit when gold cylinders that have been cyclically loaded are mated to as-manufactured abutments. MATERIAL AND METHODS: Fifteen implant-supported frameworks were fabricated using conventional casting techniques and were cyclically loaded under 3 different loading conditions: anterior region, unilaterally on posterior cantilever, and bilaterally on posterior cantilever. A cyclical load of 200 N was applied to each framework for 200,000 cycles. The abutments and frameworks were returned to the definitive casts for measurements. Linear measurements (microm) of the gap between the prosthetic cylinder and the implant-supported abutment at 4 predetermined reference points were made. The cycled abutments were replaced with as-manufactured abutments, and the gaps were measured at the same reference points. The Mann-Whitney rank-sum test was applied to the 2 sets of data to determine whether significant changes in fit were observed following component replacement (alpha = .05). RESULTS: Although minor changes in component fit were seen, the data failed to show that gaps at the prosthetic-abutment interface of cycled abutments were significantly different from those of as-manufactured abutments. CONCLUSIONS: Within the limitations of this study, differences in the fit between the implant-supported prosthesis and the abutments were not significantly different when abutments worn through loading were replaced with new as-manufactured abutments.