The purpose of this study was to evaluate the new bone formation and biodegradability of various bone fillers placed underneath a nonresorbable membrane (expanded polytetrafluoroethylene [e-PTFE]) in standardized defects in a beagle dog model. Mandibular premolars and first molars were extracted bilaterally in six adult female beagle dogs. Three months after the extractions, six rectangular defects (4 mm apicocoronally, 7 mm mesiodistally, and the entire width of the ridge buccolingually) were surgically created in the alveolar processes. All defects were covered with an e-PTFE membrane and stabilized buccally with stainless steel fixation screws. Five different bone fillers were placed under the membranes in a random configuration in each dog: autogenous bone, demineralized freeze-dried bone, anorganic bovine bone, tricalcium phosphate granules, and collagen sponge. One site in each animal was treated with the e-PTFE membrane alone. Following an 8-month healing period, a bone core was harvested from each grafted site using a trephine drill. Samples from each of the grafted sites were evaluated histologically and histometrically for their bone regenerative potential. The result of this study demonstrated a positive effect of bone fillers on bone regeneration when combined with a nonresorbable membrane; however, no significant differences were found between the various bone fillers in terms of their regenerative potential.