The influence of abutment disconnections on peri-implant marginal bone: A systematic review

To assess the failure rate of dental implants and prosthetic restoration, complications and marginal bone loss (MBL) of implants restored with an immediate definitive abutment at the time of the implant placement, and implants that were evaluated according to a standard prosthetic protocol (SPP), which includes multiple abutment changes.

This systematic review followed the guidelines of the PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). An electronic search with no date or language restriction was run in January 2018 in the PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, and complemented with a manual search. Randomised clinical trials with at least a 12-month follow-up evaluating the use of a definitive abutment and a SPP were included. The Cochrane Collaboration Risk of Bias tool was used to evaluate the included studies. The outcome measures were: implant and prosthetic failure; aesthetics; complications; and peri-implant MBL. The results were pooled using a random-effect model with mean differences (MDs) for continuous outcomes and risk ratio for dichotomous outcomes with a 95% confidence interval (CI).

The search identified a total of 714 studies. After the screening process five studies were included in the analysis. The five studies included had a limited sample size, a short follow-up period, and four studies were considered at high risk of bias. The meta-analysis revealed that five studies using an immediate definitive abutment over a 12- to 18-month follow-up resulted in lower MBL, with a MD of -0.32 mm (95% CI -0.45 to -0.19: P < 0.0000). At the end of a 3-year follow-up two studies showed a MD of -0.33 mm (95% CI -0.63 to -0.03: P = 0.03, which also favours the definitive abutment group. Regarding implant failure rate, complications, and probing depth, no significant difference was found between the groups.

Within the limitations of this meta-analysis, reducing the number of abutment changes contributes to statistically significant lower MBL. However, the clinical significance of this reduction in bone loss should be interpreted with caution. A high implant success rate was reported by all studies for both control and test groups.