OSTEOGENIC POTENTIAL OF DBP AND HYDROXYLAPATITE

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Particulate hydroxylapatite (HA) has been used to augment mandibular and maxillary atrophic ridges for over 12,000 patients in the U.S. since April, 1982. In these onlay situations the mass of HA particles is held in place by the development of dense fibrous tissue. However, significant bony ingrowth into the HA ridge is seen only when the HA is combined with autogenous cancellous bone. The ingrowth of bone into the HA ridge is thought to increase ridge stability and mandibular strength. Unfortunately, harvesting an autograft increases pain, mobidity, and hospital expense. Demineralized bone powder (DBP) induces osteogenesis. This study will evaluate the degree of induced osteogenesis throughout the HA-augmented ridge when DBP is combined with HA. DBP produced from cadaver dog long bones will be used in this study. An in vivo assay in the subcutaneous tissues in the dog's neck will confirm osteogenic induction ability for each batch of the synthesized DBP. HA and DBP in a 1:1 volume ratio will be placed in a subperiosteal tunnel on the mandibular ridge of the dogs and maintained in position by using prefabricated splints. Control materials will include HA combined with autogenous bone, and DBP alone. Sacrifice periods will provide data for 4, 12, 16, and 52 week post-augmentation comparisions. Vertical height stability will be followed by radiographic measurements using standard processing conditions. Bone formation will be identified by oxytetracycline fluorescence and histological examination will examine cellular detail. Ash content will quantitate the amount of mineralization for each specimen.