Purpose: The keratinized tissue (KT) around dental implants may be useful to ease plaque control. This meta-analysis aimed to compare peri-implant health parameters based on KT width (≥ 2 mm vs < 2 mm).

Materials and methods: A highly sensitive search of five databases was performed up to February 1, 2020. The quality of eligible studies was assessed using a modified version of the Newcastle-Ottawa checklist. A random-effects model was used to pool standardized mean differences with 95% confidence intervals. To discover sources of heterogeneity, subgroup analysis and meta-regression were used. Publication bias was evaluated by the Egger and Begg tests.

Results: From 7,934 identified studies, 22 papers were included in the meta-analysis, representing 3,004 implants in the case group (KT ≥ 2 mm) and 1,829 implants in the control group (KT < 2 mm). The results indicated that most of the parameters, including gingival recession (GR), Gingival Index (GI), modified Gingival Index (mGI), Plaque Index (PI), modified Plaque Index (mPI), bleeding on probing (BOP), modified Bleeding Index (mBI), and bone loss (BL) revealed substantial differences between the control and case groups. On the contrary, no statistically significant association was detected for pocket depth (PD) between the two groups.

Conclusion: The presence of at least 2 mm of KT around implants has a protective effect on the peri-implant tissue condition. Narrow KT was related to higher BL, BOP, mBI, GI, mGI, PI, mPI, and GR. In addition, with regard to PD, no significant difference was found.