Influence of abutment types on the success of two-unit implant-supported fixed dental prostheses: A three-dimensional finite element analysis and fatigue test combined with microleakage evaluation.

STATEMENT OF PROBLEM

Implant-supported splinted prostheses have been widely used to rehabilitate partial edentulism. However, few studies have investigated how different abutment types affect stress distribution in dental implants and the surrounding bone structures of splinted crowns. In addition, which combination of abutments helps reduce microleakage at the abutment-implant interface the most is unclear.

PURPOSE

The purpose of this study was to assess the impact of various implant abutment combinations for 2-unit implant-supported fixed prostheses on the implants and surrounding bone by using 3-dimensional finite element analysis (FEA) and to determine the microleakage of implants after fatigue testing.

MATERIAL AND METHODS

A bone block representing the mandibular posterior region was created based on cone beam computed tomography (CBCT) data. The implants used were bone-level with an internal conical connection and platform-switching design (Institut Straumann AG), which were positioned in the bone block with 4 distinct abutment (Institut Straumann AG) combinations: 2 screw-retained abutments restored with screw-retained crowns, 2 cement-retained abutments restored with cemented crowns, 2 Variobase for Bridge/Bar Cylindrical abutments, and a combination of a Variobase for a crown abutment and a Variobase for a Bridge/Bar Cylindrical abutment. A 2-unit crown for the mandibular right first molar and second premolar was designed with static and dynamic loads applied at a 30-degree angle to evaluate implant-abutment interface deformation. Fatigue testing with microleakage evaluation validated the FEA results. One-way ANOVA analyzed between-group differences, repeated-measures ANOVA evaluated microbiological data, and post hoc comparisons used the least significant difference (LSD) tests (α=.05).

RESULTS

The FEA results showed significant differences in implant-abutment interface displacement among the 4 groups, with the 2 screw-retained abutment group demonstrating the least displacement (P<.001). In vitro comparisons revealed significant differences (P<.001), where the 2 screw-retained abutment group exhibited the lowest OD values and the fewest contaminated samples.

CONCLUSIONS

Based on the FEA and fatigue testing results, the combination of 2 screw-retained abutments appears to provide the most favorable outcomes in terms of minimizing displacement and microleakage for 2-unit implant-supported fixed prostheses. Cement-retained abutments demonstrated the least favorable performance.