Keratinized mucosa, not vestibule depth, protects peri-implant tissue

Adequate keratinized mucosa width (KMW) around implants is widely accepted as protective, but whether vestibule depth (VD) — a related but distinct anatomical measure — independently contributes to peri-implant soft tissue health has been less clear. This cross-sectional study examined 129 patients with a single posterior mandibular implant, recording plaque index, probing depth, clinical attachment level, gingival bleeding time index (GBTI), VD, KMW, mucosal thickness, mucosal recession (MR), soft tissue phenotype, and peri-implant soft tissue dehiscence (PISTD) classification.

Implants with adequate KMW (≥2 mm) showed greater VD and mucosal thickness, less recession, and a thicker phenotype than those with inadequate KMW — an expected anatomical correlation. But in multiple regression analysis designed to separate the two variables, only KMW remained significantly associated with GBTI, mucosal recession, and PISTD type; VD showed no independent association with any of these outcomes once KMW was accounted for.

The cross-sectional design cannot establish whether inadequate KMW causes worse outcomes or simply co-occurs with other risk factors, and the study is limited to single implants in the posterior mandible. Still, by statistically isolating KMW from VD — two measures that are often assessed together and sometimes conflated in surgical planning — the findings sharpen the clinical target: when planning soft tissue augmentation around implants, keratinized mucosa width appears to be the parameter worth prioritizing, while vestibule depth, though anatomically related, does not independently predict inflammation or tissue stability in this cohort. This does not mean vestibule depth is irrelevant to prosthetic or hygiene access, but it does suggest that grafting decisions aimed specifically at inflammation control and tissue stability should be guided by KMW measurements rather than VD alone.