Dynamics of mucosal dimensions after root coverage with a bioresorbable membrane

Background: So far, the clinical effects of the placement of a resorbable m embrane for guided tissue regeneration have not been studied in humans in g reat detail. The dynamics of the resorptive processes, in particular, appea r to be rather speculative. In the present longitudinal study, specific alt erations of the dimensions of the dentogingival mucosa were explored after surgical root coverage by using a bioresorbable membrane and a coronally-re positioned flap. Methods: The study population consisted of 14 patients with a total of 31 p redominantly shallow, Miller class I, II or III recessions. The thickness o f the masticatory and lining mucosa before and after surgical intervention was measured with an ultrasonic device. Results: Mean (+/-sd) recession depth and width were 2.85+/-1.29 and 4.46+/ -1.14 mm, respectively. After 12 months, 51+/-29% of the recession depth (p < 0.001) and 13+/-35% of its width (n.s.) were covered. Root coverage seem s to be rather defect-type sensitive with best results obtained at canines with relatively shallow recessions. Mucosal thickness was considerably incr eased after surgery with a gradual decrease during the following 9 months. Thus, thickness of the marginal tissue rose from 0.82+/-0.27 mm to 1.49+/-0 .54 mm 3 months after placement of the membrane (p < 0.001). After 12 month s, a mean thickness of 1.03+/-0.40 mm was observed (p < 0.001). Even more p ronounced alterations were noted for the alveolar lining mucosa with a thre efold increase of thickness 3 months after surgery and a gradual decrease t o about 1 mm after 12 months. Conclusions: The present results point to the considerable space making cap acity of the bioresorbable membrane which probably allows for the ingrowth of a granulation tissue derived from the underlying structures. The gradual decline in mucosal thickness between months 6 and 9 after surgery may be p aralleled by the maturation of the granulation tissue while complete resorp tion of the membrane had been accomplished.