What Are the Effects of Different Abutment Morphologies on Peri-implant Hard and Soft Tissue Behavior? A Systematic Review and Meta-Analysis.

To evaluate the effect of different abutment morphologies on peri-implant hard and soft tissue behavior. The focus question for this literature search was: What are the effects of different abutment morphology (concave vs convex) on peri-implant hard and soft tissue behavior? Randomized clinical trials (RCTs) with a minimum sample size of 20 implants (10 per group) and a follow-up period of at least 3 months after implant loading were considered eligible for this study. This review excluded studies comparing different abutment heights or surfaces and different implant shapes. Two different meta-analyses were performed: one for marginal bone loss (MBL) to evaluate hard tissue changes, and one for Pink Esthetic Score (PES) as an indicator of soft tissue modifications. Four publications from 12 full texts analyzed were included. The meta-analysis (data from 117 patients and 173 abutments) indicated that a statistically significant difference (P < .00001) was detected from the data regarding MBL between the two groups (mean difference = -0.21 [95% CI: -0.25, -0.16]), but not considering the PES (mean difference = -0.69 [95% CI: -2.08, 0.70]) after a minimum period of 3 months after implant loading. All such evidence was confirmed by the trial sequential analysis on both MBL and PES. The results demonstrate that abutment design may have an influence on MBL but no impact on soft tissues. However, the existing evidence is moderate, as few RCTs were conducted and follow-up periods were short.