Influence of the Presence of Alveolar Mucosa at Implants: A Histological Study in Humans

Objective: To evaluate the influence of the presence or absence of keratinized mucosa on hard and soft tissues around implants. Material and Methods: Sixteen volunteers with edentulous regions in the distal aspect of the mandible participated in the study. In each patient, 2 solid titanium screw-shaped devices, 3.5 mm in diameter and 5 mm long, were installed. The incision of the mucosa was performed in such a way to allow that, after the suture of the flaps, only the alveolar mucosa surround the test sites and the keratinized mucosa surround the control implants. After 3 months of healing, biopsies were retrieved and ground sections were prepared for histological analysis. Results: Eighteen biopsies from 9 patients were collected for analysis. Both buccal bone resorption and most coronal level of osseointegration were higher at the test sites compared with the control sites, the difference between the 2 sites being 0.2 and 0.5 mm, respectively. The difference in the coronal level of osseointegration between the test and control sites was statistically significant. Mineralized bone-toimplant contact was 70.6% +/- 10.9% at the test sites and 71.5% +/- 9.2% at the control sites. Conclusions: The presence of alveolar mucosa at implants resulted in a more apical position of the coronal level of osseointegration in respect of the implant margin compared with the presence of keratinized mucosa.