Biomechanical evaluation of abutment stability in morse taper implant connections in different times: A retrospective clinical study compared with an in vitro analysis

OBJECTIVES: Micromotion between a dental implant and abutment can adversely affect clinical performance and compromise successful osseointegration by creating a bacterial harbor, enabling screw loosening, and imparting disruptive lateral forces on the cortical bone. Thus, the aim of the present study was to measure the abutment stability evolution using resonance frequency analysis (RFA) in vivo at four different times (baseline, 3, 4, and 12 months), and compare these data obtained with the RFA measured after mechanical cycling (in vitro) corresponding to the proposed times in numbers of cycles. METHODS: To evaluate the abutment stability, RFA was performed in 70 sets of implant/abutment (IA) with a total of 54 patients (31 women, 23 men). These IA sets were divided into three groups, according to the abutment angulation: straight abutment (Abt1 group), 17-degree angled abutment (Abt2 group), and 30-degree angled abutment (Abt3 group). Abutment stability was measured immediately at implant placement and the abutment installation (T1), 3 (T2), 4 (T3), and 12 months (T4) later. For the in vitro analysis, ten sets of each group were submitted to mechanical cycling: T1 = 0 cycles, T2 = 90,000 cycles, T3 = 120,000 cycles, and T4 = 360,000 cycles. All data collected were statistically evaluated using the GraphPad Prism 5.01 software, with the level of significance was α = 0.05. RESULTS: In vivo, the overall data of implant stability quotient (ISQ) values obtained for all groups in each evaluation time were 61.5 ± 3.94 (95% CI: [60–63]) at T1, 62.8 ± 3.73 (95% CI, [61–64]) at T2, 63.4 ± 3.08 (95% CI: [61–64]) at T3, and 65.5 ± 4.33 (95% CI: [63–68]) at T4. Whereas in vitro, the ISQ were 61.5 ± 2.66 (95% CI: [59–63]) at T1, 63.2 ± 3.02 (95% CI, [61–65]) at T2, 63.9 ± 2.55 (95% CI: [62–66]) at T3, and 66.5 ± 2.97 (95% CI: [64–68]) at T4. In both evaluations (in vivo and in vitro), the data showed a significant difference (ANOVA test with p < 0.0001). CONCLUSIONS: The RFA to measure the abutment stability used in this study showed that there was a progressive increase in stability among the predetermined times for the measurements, in both analysis (in vivo and in vitro). Furthermore, the values at each time point were similar, with no statistical difference between them.