Significance of peri-implant keratinised mucosa on implant health: An umbrella systematic review with evidence mapping and quantitative meta-meta-analysis

Purpose: To conduct a comprehensive umbrella review to synthesise existing evidence and critically evaluate the significance of keratinised mucosa width in peri-implant health and assess the consistency and heterogeneity among previous systematic reviews on this topic.
Materials and methods: A comprehensive search strategy was implemented across multiple databases. Eligible studies were screened and data were extracted. Methodological quality was assessed using A MeaSurement Tool to Assess systematic Reviews version 2, and strength of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation criteria. A meta-meta-analysis using Hedges’ g as the effect size measure was performed to investigate the outcomes of implant therapy in patients with (control) and without adequate keratinised mucosa width (case).
Results: Ten systematic reviews, published between 2012 and 2023, were included. Significant effect sizes were found for mucosal recession, Gingival Index/modified Gingival Index, modified Plaque Index and marginal bone loss. Specifically, narrow keratinised mucosa width ( 2 mm) was associated with increased mucosal recession (equivalent odds ratio 4.05, P = 0.03), higher Gingival Index/modified Gingival Index scores (equivalent odds ratio 3.131, P = 0.001), elevated modified Plaque Index scores (equivalent odds ratio 5.34, P = 0.005) and greater marginal bone loss (equivalent odds ratio 1.852, P = 0.0007). No significant associations were observed for bleeding on probing, pocket depth changes or pocket depth values. Follow-up time did not have a significant effect on these outcomes.
Conclusions: Inadequate keratinised mucosa width ( 2 mm) correlated with increased mucosal recession, higher Gingival Index/modified Gingival Index, Plaque Index/modified Plaque Index scores and greater marginal bone loss. However, there is still a lack of sufficient evidence indicating the impact on bleeding on probing, pocket depth, implant survival and disease prevalence (no significant association or insufficient evidence).