Soft tissue stability related to mucosal recession at dental implants: a systematic review

To assess the stability of soft tissues around implants by comparing mucosal recessions in patients with keratinized mucosa (test) with patients without keratinized mucosa (control) around osseointegrated dental implants.

The PICO criteria used were as follows: Population, patients with osseointegrated dental implants; Intervention/exposure, presence of a keratinized mucosa; Comparison/control, absence of keratinized mucosa; Outcome, presence or absence of peri-implant mucosal recessions (mm).

An electronic search of Medline, Embase, and Cochrane Oral Health Group specialist trials supplemented by manual searching was conducted to identify studies reporting outcomes of at least 5 years on the presence of mucosal recessions at implants with or without attached mucosa. Mucosal recession (MR) was set as primary outcome. Prospective cohort studies published in English language up to October 2018, with a mean follow-up period of at least 5 years, reporting keratinized tissue height ≥ 2 mm and < 2 mm or presence/absence of keratinized tissue, with fixed implant-supported prostheses. The homogeneity of studies was assessed by DerSimonian and Laird test (Q test). The differences in terms of gingival recession around implants reported between test groups (keratinized mucosa ≥ 2 mm) and control (keratinized mucosa < 2 mm or no keratinized mucosa) were compared. Two studies reporting 201 patients with 514 tissue level implants were selected for the final analysis.

Due to the high heterogeneity between the selected studies, no statistical test could be performed. However, in both studies a deeper mucosal recession occurred when keratinized mucosa was < 2 mm: 0.61 ± 0.10 (-0.90; -0.32) and -1.92 ± 0.12 (-2.16; -1.68), respectively.

Within their limitations, the findings indicate that after a mean observation period of at least 5 years, the presence of keratinized mucosa may lead to less mucosal recession at dental implants.