Membranes are utilized in guided bone and tissue regeneration procedures. They act as mechanical and biological barriers against soft tissue and other cells not required for bone formation that can invade the surgical space. There are generally two types of membranes — non-resorbable and resorbable. A non-resorbable membrane cannot be absorbed by the body during healing, because it is created from a high-density and microporous dPTFE, also known as polytetrafluoroethylene. This material is considered biologically inert and does not react to chemicals, making it a good choice for the moist, bacteria-filled environment of the mouth. However, it does need to be surgically removed after a period of a few weeks after bone growth has occurred. In contrast, a membrane made from bioresorbable polyactide (PLA) can be used to help create blood clot formation that is conducive to healing and promotes healthy blood flow. Both types of membrane have had good clinical results.