Effects of Gingival Augmentation on Peri-implant Bone Loss

Objectives: Many studies have discussed the necessity of keratinized mucosa (KM) around dental implants. However, there is no consensus. This multicenter retrospective longitudinal study aimed to clarify the significance of KM for preventing the peri-implant bone loss and clinical efficacy of augmentation techniques used to increase the KM around dental implants.
Methods: Patients were enrolled from eight institutes. Clinical data and treatment histories were collected. Bone loss (BL) was calculated by comparing dental X-rays at baseline and follow-up (over 3 years from baseline). Based on keratinized mucosa width (KMW), implants were categorized as follows: received free gingival grafts or apically repositioned flap surgery (group A), KMW ≥ 2 mm (group B) and KMW < 2 mm (group C). A generalized linear regression analysis for comparing the BL among 3 groups was weighted by propensity score in order to reduce the following biases: age, gender, follow-up period, history of periodontitis, diabetes, smoking, plaque control record, number of teeth and clinician.
Results: 1634 implants (84 in group A, 987 in group B, 563 in group C) were placed in 543 patients with a mean age of 57.5 years. Mean follow-up period were 4.65 years in group A, 5.64 years in group B and 6.24 years in group C. Mean BL of group A, B and C were 0.08 mm, 0.18 mm and 0.43 mm, respectively. On the reference of group C, unstandardized regression coefficients (B) and P-values were estimated. The result of estimation showed that both group A (B = -0.35, P < 0.01) and B (B = -0.20, P < 0.01) had significantly lower BL than group C.
Conclusions: These results suggest that lack of KM around dental implants should be considered as a risk factor for bone resorption. Moreover, gingival augmentation around dental implants would produce a beneficial effect on reduction of bone loss.