Ridge Preservation in Molar Sites Comparing Xenograft Versus Mineralized Freeze-dried Bone Allograft

Inclusion Criteria: * Adult patients, over 18 years old. * In need of removal of a maxillary or mandibular molar first or second molar. * The molars to be extracted had to be bordered by at least one tooth. * The molars had to have a presence of \> 2 mm of keratinized gingiva and three intact bony walls. * A dehiscence on the fourth wall, if any, had to be equal or less than 2 mm in height. * Only one extraction per patient was accepted. Exclusion Criteria: * Acute periodontal or periapical infection. * Pregnancy or lactancy. * Smokers of more than 10 cigarettes per day. * Previous adverse reactions to the biomaterials used in the study. * Metabolic diseases affecting the mechanism of bone remodelling. * Medications or treatments taken in the last twelve months and known to affect bone "turnover". * Patients with poor plaque control -more than 20% (O'Leary, Drake, Naylor, 1972). * Patients with absence of periodontal health maintenance or postoperative recommendations compliance.