Biological effect of the abutment material on the stability of peri-implant marginal bone levels: A systematic review and meta-analysis

Objectives: The primary aim of this systematic review was to evaluate the available evidence on the effect of the abutment material on the stability and health of the peri-implant hard tissues. Methods: A protocol was developed to answer the following focused question: "Which is the effect of the abutment material on stability and health of the peri-implant hard tissues?" Randomized controlled trials (RCTs), controlled clinical trials (CCTs) or prospective case series (CS) with at least 6 months of follow-up were included, and meta-analyses were performed to compare abutment materials vs. titanium and to evaluate the impact of various abutment materials on bone changes (primary outcome), probing depth, plaque levels and peri-implant mucosal inflammation. Results: Twenty-nine publications from 33 investigations were included. Results from the meta-analyses demonstrated no significant differences between the different abutment materials when compared to titanium, in regard to the changes in marginal bone levels (MBLs) (n = 15; WMD = 0.034; 95% CI [-0.04, 0.10]; p < 0.339). The meta-analysis reported a significantly greater increase in bleeding on probing for titanium compared to zirconia abutments (n = 3; WMD = -26.96%; 95% CI [-45.00%, -8.92%]; p = 0.003). When evaluating the behaviour of each material different to titanium, there was a significant bone loss over time (n = 31; WMD = 0.261; 95% CI [0.18, 0.35]; p < 0.001) for all the individual materials except for titanium nitride. Conclusions: This systematic review has shown that the abutment material had minimal impact on marginal bone levels when compared to the standard titanium.