Impact of prosthetic abutment design on peri‐implant clinical and esthetic outcomes: A systematic review and meta‐analysis of randomized controlled trials

PURPOSE: To investigate, based exclusively on randomized controlled trials (RCTs), the current evidence on the influence of different prosthetic abutment designs on peri-implant clinical outcomes and esthetic parameters. METHODS: This systematic review and meta-analysis of RCTs was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. A comprehensive and systematic search was conducted across multiple databases and gray literature, including MEDLINE/PubMed, Scopus, Web of Science, Embase, ReBEC, Trials, Virtual Health Library, and ProQuest, to identify RCTs comparing different abutment designs. Abutments were categorized into narrowed (concave, curved), straight (linear, convex, cylindrical), and widened (wide) profiles. The primary outcomes were marginal bone loss (MBL), probing depth (PD), and Pink Esthetic Score (PES), all assessed through meta-analyses. Secondary outcomes included abutment survival, biological and technical complications, as well as additional aesthetic parameters, including mid-facial mucosal zenith (MMZ), keratinized mucosa width (KMW), mucosal thickness (MT), mucosa position (MP), and soft tissue profile (SP). Risk of bias was assessed using the Cochrane RoB 2.0 tool, and the certainty of evidence was evaluated according to the GRADE approach. RESULTS: The search resulted in 10,566 studies; after removal of duplicates, 5270 studies remained. Of those, 5252 were excluded based on title and abstract screening. Ultimately, 10 RCTs with follow-ups ranging from 3 to 60 months were included for quantitative and qualitative assessments. Of these, six provided data that could be pooled and were included in the quantitative analysis. Risk of bias varied among studies, with high risk observed in 2 RCTs, some concerns in 5 studies, and low risk in 3 studies, primarily related to outcome measurement and blinding, as assessed using the RoB 2.0 tool. Overall certainty of evidence was rated moderate. The meta-analyses showed no statistically significant difference in MBL, PD or PES between narrowed and straight profiles (MBL: SMD = 0.08, p = 0.66); PD: SMD = -0.05, p = 0.80; PES: SMD = -0.12, p = 0.51). Additionally, no differences were found in biological or esthetic outcomes between abutment types, with stable peri-implant parameters and high patient satisfaction. Technical complications were rare, involving early failures and occasional fractures, especially in concave abutments. CONCLUSION: Based on the current evidence and within the limitations of the included studies, abutment shape does not appear to significantly influence peri-implant tissue response or esthetic outcomes. Further well-designed RCTs with standardized protocols, adequate sample sizes, and longer follow-up are required to increase the certainty of the evidence and improve the external validity of the findings.