Multivariate analysis of the effect of keratinized mucosa on peri-implant tissues with platform switching: A retrospective study

Background: In recent years, platform switching implant treatment has been increasing, which is believed to minimize bone loss around the implant after placement. However, there have been no reports on the relationship between keratinized mucosa width (KMW) and bone loss and soft tissue recession in platform switching implants. Objective: We evaluated the effect of the KMW on the amount of bone loss and soft tissue recession around a platform switching implant retrospectively using multivariate analysis. Materials and Methods: This one-year retrospective study included 91 implants in 48 patients. Age, sex, a history of periodontitis, implant location, oral hygiene status, and the KMW were included as explanatory variables to evaluate bone loss (BL) and buccal gingival height (GH). Generalized estimating equations (GEEs) were used to evaluate the effect of the KMW on platform switching peri-implant tissues. Results: The mean bone loss on the mesial (Delta BLm), distal (Delta BLd), and buccal (Delta BLb) sides of the implant were 0.16 +/- 0.27 mm, 0.19 +/- 0.34 mm, and 0.24 +/- 0.50 mm, respectively, at 1 year after superstructure placement. The mean amount of change of GH (Delta GH) on the buccal side was 0.30 +/- 0.47 mm. After correcting for confounders using GEEs, the results suggested that KMW <1.5 mm was a significant factor (P < 0.001) for bone loss over time in Delta BLm, Delta BLd, and Delta BLb. In addition, for soft tissues on the buccal side, KMW <1.5 mm was a significant factor for Delta GH reduction over time (P < 0.001). Conclusions: Keratinized mucosa width >= 1.5 mm was associated with a higher probability less hard and soft tissue recession around the platform switching implant after 1 year from superstructure placement.