Studies on dentin grafts to bone defects in rabbit tibia and mandible; development of an experimental model

Dentin contains bone morphogenic protein which is important in bone induction and dentin can act as a slow releasing carrier. This property may possibly be used as an alternative or supplement to bone grafting to defective areas after trauma prior to treatment with osseointegrated implants. Hence, the objective of this study was to investigate if dentin can be used as a graft in bone defects in an experimental rabbit model.

Eight New Zealand White Rabbits were used to prepare bone cavities either in the angle of the mandible or tibia. Six of the eight tibial and six of the eight mandibular bone defects were filled with dentin blocks from human premolars which were extracted for orthodontic treatment. Two mandibular and two tibial bone cavities were used as controls and all the rabbits were sacrificed after 3 months. Radiographic and histological examinations were performed.

There was a difference in healing pattern between the mandibular and tibial defects. In the mandible, the dentin blocks were resorbed to a larger extent and more often surrounded by fibrous tissue, probably due to the fact that the dentin blocks were mobile because of the thin mandibles and muscular activity in that area. Only some dentin blocks were ankylosed with the mandibular bone. In the tibia however, all dentin blocks were fused to bone over a large area. Osseous replacement resorption was seen. In control cavities, bone formation was seen but was never complete. No signs of inflammatory changes were seen in any fused grafts.

Dentin grafts have a potential to be incorporated in bone without inflammation and can be used as bone inducer and later replaced by bone. Thus, rabbit tibia served as a better model for further studies of this phenomenon when compared to the mandible.