When a membrane becomes exposed to the oral environment there is a risk of infection producing untoward effects to the regenerating environment. This scenerio is unpredictable and whether or not healing is progresseing beneath an exposed membrane is usually a guess. The greater length of time for the exposure, the more risk of degeneration and infection. There have been studies which demonstrate that membranes which have been exposed show diminished levels of regenerative tissue groth.
Bacterial penetration following exposure is believe to occur around week four.