I tested the effectiveness of a particulate dentin and plaster of Paris mixture as a bone substitute. Histologic analysis indicated that all of the bone defects surrounding the implants treated with particulate dentin/plaster of Paris were filled with new bone 6 and 12 weeks after surgery. No significant differences were observed in the new bone forming activity in any species (human, bovine, pig, rabbit, and dog). No cytotoxicity was detected in cell cultures with added particulate dentin extract and no specific allergic reactions were seen in the hypersensitivity test. These results suggested that the combination of particulate dentin and plaster is suitable as an alternative bone substitute.