Clinical study on the association between keratinized mucosa and peri-implant health when external hexagon implants are installed in the posterior region of the maxilla and mandible: a cohort study

This study evaluated the association between keratinized mucosa (KM) and peri-implant health of external hexagon implants in the posterior region in 84 patients with 242 implants. Modified plaque index (MPI), modified sulcular bleeding index (MSBI), probing depth (PD), keratinized mucosa (KM) width, and peri-implant bone loss were evaluated. The implants were divided according to the KM: (1) absence of KM, (2) KM width >0 and <2 mm, and (3) KM width ≥2 mm. Of the 242 implants evaluated, 63 (26.0%) had no KM band, 56 (23.1%) had KM width <2 mm, and 123 (50.8%) had KM width ≥2 mm. One hundred and sixty-seven (69.0%) were used in multiple unit restorations and 75 (31.0%) in single tooth restorations; 66.9% were placed in the mandible and 33.1% in the maxilla. For single tooth and multiple unit implant restorations, MPI (P=0.069 and P=0.387, respectively), MSBI (P=0.695 and P=0.947, respectively), PD (P=0.270 and P=0.258, respectively), and mesial bone loss (P=0.121 and P=0.239, respectively) were not affected by the KM width. On the distal surface, bone loss was influenced by the absence of KM when single tooth implant restorations were used (P=0.032). No association was found between KM width and the peri-implant tissue health.