Flap thickness as a predictor of root coverage: A systematic review

Background: Thick gingival tissue eases manipulation, maintains vascularity, and promotes wound healing during and after surgery. A few recent case reports correlate greater flap thickness to mean and complete root coverage after mucogingival therapy for recession defects. The aim of this systematic review is to appraise the current literature on this subject and to combine existing data to verify the presence of any association between gingival thickness and root coverage outcomes. Methods: Human studies that reported the number and class of recessions, measured flap thickness at a well-defined location, described the method of root coverage used, followed results for at least 3 months, and detailed mean root coverage underwent review and statistical analysis. Investigations were scored from I to 5 based on methodological quality. Weighted gingival thickness and weighted mean root coverage was calculated based on standard error. Statistical analysis used the Mann-Whitney test, analysis of variance (ANOVA), and linear regression to determine any correlation between a number of factors (i.e., thickness, treatment type, and follow-up time) and mean and complete root coverage. A significant P value was set at < 0.05. Results: Fifteen investigations met the inclusion criteria. All of these reported at least 0.7 mm of flap thickness, although measurement locations varied. Treatment modalities included coronally advanced flap, connective tissue graft, and guided tissue regeneration with and without adjuncts. A significant moderate correlation occurred between weighted flap thickness and weighted mean root coverage and weighted complete root coverage (r = 0.646 and 0.454, respectively). According to Mann-Whitney analysis, a critical threshold thickness > 1.1 mm existed for weighted mean and complete root coverage (P < 0.02). The type of treatment rendered also influenced root coverage. Further simple linear regression revealed a high correlation between weighted thickness and weighted mean root coverage in connective tissue grafting and guided tissue regeneration (r = 0.909 and 0.714, respectively) but not coronally advanced flap therapy. Study score and follow-up time did not affect the percentage of root coverage. Conclusion: Within the limits of this review, a positive association exists between weighted flap thickness and mean and complete root coverage.