Association of vestibule depth with peri-implant inflammation and soft tissue stability independent of keratinized mucosa width: A cross-sectional study

Purpose: This study evaluated whether vestibule depth (VD) affects peri-implant inflammation and mucosal margin stability in the posterior mandible independently of keratinized mucosa width (KMW). Methods: A total of 129 patients, each with a single implant in the mandibular premolar or molar region, were included. Clinical variables, including gingival index, plaque index (PI), peri-implant probing depth, clinical attachment level (CAL), gingival bleeding time index (GBTI), VD, KMW, mucosal thickness (MT), mucosal recession (MR), peri-implant soft tissue phenotype, and peri-implant soft tissue dehiscence (PISTD), were assessed. Multiple linear regression analysis was performed to determine the associations of GBTI, MR, and PISTD type with the independent variables PI, KMW, age, implant diameter, sex, function time, implant location, CAL, MT, VD, and phenotype classification. Results: Implants with adequate KMW (≥2 mm) displayed greater VD and MT, less MR, and a thicker phenotype than implants with inadequate KMW (<2 mm) (P<0.001 for all). PISTD class II defects were observed more frequently in the group with adequate KMW, whereas class III defects were more common among the patients with inadequate KMW (P=0.001). Implants with sufficient VD (≥6 mm) showed greater KMW and MT and less MR than implants with insufficient VD (<6 mm) (P=0.026 for MR; P<0.001 for all other comparisons). Based on the multiple regression analysis, KMW was significantly associated with GBTI, MR, and PISTD types and subtypes (P<0.05 for all), whereas VD was not significantly associated with any of these variables. Conclusions: VD was not significantly associated with peri-implant inflammation or soft tissue stability, whereas KMW showed a stronger association with these parameters. These findings suggest that KMW, independent of VD, plays an important role in peri-implant soft tissue health in the posterior mandible.