The Significance of Keratinized Mucosa on Implant Health: A Systematic Review

Background: Whether a minimal width of keratinized mucosa (KM) is required to maintain peri-implant tissue health has been a topic of interest. This systematic review and meta-analysis aims to investigate the effect of KM on various peri-implant health-related parameters. Methods: An electronic search of five databases (from 1965 to October 2012) and a hand search of peer-reviewed journals for relevant articles were performed. Human cross-sectional or longitudinal studies with data on the relationship between the amount of KM around dental implants and various peri-implant parameters, with a follow-up period of at least 6 months, were included. Results: Eleven studies, seven cross-sectional and four longitudinal, were included. Weighted mean difference (WMD) and confidence interval (CI) were calculated with meta-analyses for each clinical parameter. The results showed statistically significant differences in plaque index (PI) and modified PI (WMD = -0.27, 95% CI = -0.43 to -0.11), modified gingival index (mGI) (WMD = -0.48, 95% CI = -0.70 to -0.27), mucosal recession (MR) (WMD = -0.60 mm, 95% CI = -0.85 to -0.36 mm), and attachment loss (AL) (WMD = -0.35 mm, 95% CI = -0.65 mm to -0.06 mm), all favoring implants with wide KM. However, comparisons of other parameters (bleeding on probing, modified bleeding index, GI, probing depth, and radiographic bone loss) did not reach statistically significant differences. The result of heterogeneity test showed only one parameter (AL, P value for the x(2) test = 0.30 and I-2 test = 18%) had a low degree of heterogeneity among analyzed studies; meta-analyses of other parameters presented moderate- to-high degree of heterogeneity. Limitations of the present review include limited number of selected studies (n = 11), existence of heterogeneity and publication bias, and only English-written articles searched. Conclusion: Based on current available evidence, a lack of adequate KM around endosseous dental implants is associated with more plaque accumulation, tissue inflammation, MR, and AL.