Modeling mucosal dimensions after implantation of a bio-absorbable membrane for surgical root coverage

The aim of this study was to model alterations of mucosal thickness after implantation of a bio-absorbable membrane for surgical root coverage employing guided tissue regeneration. Periodontal conditions around 31 recession sites in 14 patients were assessed for up to 12 months after surgery. Mucosal thickness was modeled in a multivariate, three-level (occasion, tooth, subject) time series model. The amount of root coverage was studied in a bivariate multilevel model of change and mean recession to avoid mathematic coupling. Predictions of gingival thickness were, at the outset, strongly related to baseline gingival width. At maxillary teeth, gingival thickness at all measurement locations peaked 3 months after surgery with negative relations to baseline gingival width. Thereafter, thickness gradually decreased but remained higher (0.3-0.5 mm, 95% confidence interval 0.05-0.9 mm) than before surgery, while positive correlations with baseline gingival width were re-established. At mandibular teeth, gingival thickness did not change so dramatically, while thickness of lining mucosa underwent similar changes as at maxillary teeth. In contrast to previous publications, modeling change of recession depth and mean recession did not yield better results in deeper sites when applying a bivariate multilevel model that avoids mathematic coupling.