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Associated Topics

Keratinized mucosa may have benefits for peri-implant tissue health

Yumi Ogata DDS, MSc; Yong Hur DDS, DMD, MS .


Systematic Review Conclusion

Wide keratinized mucosa (KM) (1 mm and above) compared to narrow KM (<1 mm) may have benefit on some peri-implant gingival health-related parameters.

Critical Summary Assessment

Although this well-conducted systematic review finds significant differences in some clinical parameters favoring a minimum width of KM to maintain peri-implant health, the benefit remains uncertain because of limitations in the evidence such as few included studies, study variability, and statistical heterogeneity.

Evidence Quality Rating

Limited Evidence

Structured Abstract

Clinical Questions:

For patients who receive dental implants, does the width of keratinized mucosa (KM) affect peri-implant health-related factors?

Review Methods:

The authors searched five electronic databases from 1965 to October 2012 for studies published in English. A hand search was performed of 14 dental and implant-related journals. One author conducted the searches. Two reviewers examined potential articles, and the selection of studies was confirmed by discussion. The level of agreement between reviewers was evaluated by kappa statistics. The authors included cross-sectional or longitudinal human studies with data on the relationship between the KM width and various peri-implant tissue health-related parameters with a follow-up period of at least 6 months. Reviews and case reports were excluded. Two authors extracted data independently from the included articles. The authors chose the primary outcome measures as plaque index (PI) and modified PI (mPI) and pooled the results. They chose eight other clinical parameters as secondary outcomes: bleeding on probing (BOP), modified bleeding index (mBI), gingival index (GI), modified GI (mGI), probing depth (PD), mucosal recession (MR), radiographic bone loss (BL) and attachment loss (AL). The risk of bias was assessed with criteria of Kahn et al [1]. The authors conducted random-effects meta-analysis to assess differences in outcomes using weighted mean differences (WMD). They also assessed publication bias (with funnel plots) and heterogeneity (with X2 and I2 tests).

Main Results:

Eleven articles were included in the review. Seven studies were cross-sectional and four studies were longitudinal with a mean loading period on the implants of 50.7 months. Smokers were included in six studies. The results showed statistically significant differences in four of nine peri-implant parameters (PI/mPI: WMD = -0.27 mm, 95% confidence interval (CI) = -0.43 to -0.11; mGI WMD = -0.48, 95% CI = -0.70 to -0.27; MR: WMD = -0.60 mm, 95% CI = -0.85 to -0.36; and AL: WMD = -0.35 mm, 95% CI = -0.65 to -0.06), all favoring implants with wide KM. However, differences from other parameters (BOP, mBI, GI, PD, BL) were not statistically significant. There was substantial heterogeneity among the studies for all parameters but one (AL), which showed a low degree of heterogeneity.


A lack of adequate KM (less than 1mm) around dental implants is associated with more plaque accumulation, tissue inflammation, MR and AL.

Source of Funding:

The review was partially supported by the University of Michigan Periodontal Graduate Student Research Fund.


Importance and Context:

The clinical question concerning whether a minimal width of KM is beneficial to peri-implant tissue health has been a topic of interest. Although many studies investigated different variables to answer this question, there is a lack of agreement from these studies. This systematic review attempts to fill this gap.

Strengths and Weaknesses of the Systematic Review:

This was a well-conducted systematic review and meta-analysis utilizing a comprehensive search strategy, defined inclusion/exclusion criteria, risk of bias assessment, standard data extraction methods, and standard statistical methods.. In addition to standard meta-analyses, the authors also conducted meta-analyses further stratified the results by type of prosthesis (fixed/removable) and measurement site (buccal/lingual). Authors adhered to the PRISMA statement. The weaknesses of this review were: 1) inclusion of only studies published in English and 2) lack of explanation of PI as the primary outcome for implant health.

Strengths and Weaknesses of the Evidence:

There were few studies that met inclusion criteria (n=11), which exhibited moderate-to-high heterogeneity possibly due to unadjusted confounding factors such as smoking and other methodological differences. Although four of nine parameters showed statistical differences, none of the clinical trials reported all nine peri-implant health-related parameters. As a result, the meta-analyses were conducted on three to ten studies. The authors assessed the eleven studies (seven cross-sectional and four longitudinal) as having moderate-to-high risk of bias.

Implications for Dental Practice:

This review reports that a wide (compared to narrow) KM improves gingival health around dental implants. However, the conclusion of the review is compromised due to the limited evidence quality and quantity. While recent reviews concerning the same topic have reported similar results, the direct benefit from of KM to maintain peri-implant health remains unclear. Further high quality, well-designed studies are needed to confirm the benefit of wide KM. References: 1. Kahn K, ter Riet G, Popay J, Nixon J, Kleijen J. Stage II: Conducting the Review. Phase 5: Study Quality Assessment. York, UK: Centre for Reviews and Dissemination, University of York; 2001: 1-20.

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2019