The effect of membrane exposure on the outcome of regenerative procedures in humans: A meta-analysis

Background: The significance of early membrane exposure on the regenerative outcome in guided tissue regeneration (GTR) and guided bone regeneration ( GBR) procedures is somewhat controversial, Several clinical trials have sho wn better response when the membranes remained submerged (S) compared to th ose that have become exposed (E) during healing. Other studies have failed to show any such difference. Small sample size and/or large standard deviat ion of the changes might account for these discrepancies. The purpose of th is meta-analysis is to critically combine the existing data in order to pro vide meaningful information based on a large database. Methods: Studies of GTR in Class II furcation and intrabony defects (IBD), together with GBR around dental implants, where the membrane became exposed during the postoperative period, were combined to form 3 separate database s. A meta-analysis was employed to compare the 2 subgroups (E versus S) in each of the databases. First, weighted mean changes and weighted standard e rrors were calculated for each subgroup. Next, an individual study P value was calculated (1-tailed Student t test); finally a combined Fisher's P sta tistic (with 5% significance level) was calculated from the individual P va lues. Results: Five studies with a total of 101 sites were included in the furcat ion database; 43 of these sites became exposed. Mean horizontal attachment level (AL) gain for the S sites (3.72 +/- 0.15 mm) was slightly greater tha n that of the E sites (3.06 +/- 0.15 mm; P = 0.030257). For the intrabony g roup, there were 309 sites in 5 studies: of these, 142 sites became exposed . Mean gain in vertical AL was 4.22 +/- 0.15 mm and 4.69 +/- 0.13 mm for th e E and S group, respectively (P = 0.011415). The GBR group included 60 sit es in 2 studies: new bone formation in the 24 S sites (3.01 +/- 0.38 mm) wa s 6-fold greater compared with the 36 E sites (0.56 +/- 0.45 mm). These dif ferences were also statistically significant (P = 0.001875). Conclusions: Membrane exposure during healing had a major negative effect o n GBR around dental implants but only a minimal effect on GTR around natura l teeth.