There are a variety of membrane materials on the market, both resorbable and non-resorbable. How do you choose which membrane material is best for each type of bone grafting procedure? When would you go with a resorbable over a non-resorbable? And for the resorbable collagen membranes, which resorption times are expected for specific procedures, i.e. would 6 to 9 months resorption work for the vast majority of cases? Thanks.