Evaluation of Fracture Load of Cement-, Screw-, and Multiscrew-Retained Abutments for Implant-Supported Fixed Partial Dentures.

PURPOSE The purpose of this in vitro study was to evaluate the load-to-fracture values of cement-, screw-, and multiscrew-retained abutments for implant-supported fixed partial dentures (FPDs). MATERIALS AND METHODS Thirty-six implants with a diameter and length of 4.5 and 13 mm, respectively, were used to prepare 18 samples of FPDs. Based upon the variations on abutment design, the FPDs were divided into three categories as follows: cement-retained, screw-retained, and multiunit screw-retained abutments. Using a chewing simulator, cyclic loads of 1,250,000 load cycles with a load of 70 N were applied on all samples to simulate 5 years of human functional chewing. The samples were loaded until failure using an electromechanical test machine. Sample-size estimation was done, and fracture-load values were recorded as means and corresponding standard deviations; group comparisons were done using one-way analysis of variance and Tukey post hoc tests. A P value < .01 was considered as an indicator of statistical significance. RESULTS The fracture-load values for cement-, screw-, and multiunit screw-retained abutments were 2,109.2 ± 139.6 N, 3,888.8 ± 70 N, and 3,319.4 ± 218.9 N, respectively. The load-to-fracture values were significantly higher in screw-retained abutments (3,888.8 ± 70 N; P < .001) than in cement-retained (2,109.2 ± 139.6 N) and multiunit screw-retained abutments (3,319.4 ± 218.9 N). CONCLUSION Screw-retained implant-supported FPDs withstand higher occlusal forces compared with cement- and multiunit screw-based retention techniques. However, the results should be cautiously interpreted, as they were based on a relatively small sample size.