Abstract: BACKGROUND: Autogenous dentin particles are increasingly used in various bone augmentation surgeries. Moderate demineralization may expose collagen and growth factors on the dentin surface and promote bone regeneration, but the degree of demineralization has not been clearly reported.
OBJECTIVE: To evaluate the efficacy of autogenous dentin particles demineralized with different degrees as bone graft materials on promoting bone regeneration in alveolar bone site preservation.
METHODS: Six beagles were selected and the second, third and fourth premolars of bilateral mandible were extracted. After grinding, crushing, sifting, pickling, disinfection and cleaning, dentin particles with a diameter of 0.5-1.0 mm were prepared. According to the time of pickling in 2% nitric acid, the samples received undemineralized (0 minute), demineralized for 1 minute (mild), demineralized for 10 minutes (moderate) and demineralized for 40 minutes (severe). The prepared dentin particles were filled into the tooth socket respectively, and the extraction socket without implanted dentin particles was a blank control. At 6 months after surgery, the bone graft area was observed by gross inspection, radiographic examination, and histological observation.
RESULTS AND CONCLUSION: (1) Gross observation: The crests of alveolar ridge in the dentin particle groups were full and discontinuous crest with depressions was found in blank control group. (2) Cone beam CT showed that continuous alveolar ridge was formed in the dentin particle groups, discontinuous alveolar ridge and low density in the center of alveolar bone in the blank control group, and uneven density in alveolar socket in the undemineralized and mild demineralized groups with scattered high density image. Uniform and higher density was displayed in alveolar sockets of the moderate demineralized group and the alveolar sockets in the severe demineralized group were empty with low density images. (3) Histological observation: A large amount of dentin particles and insect phagocytic defects in the particles of the undemineralized group were found to be surrounded by scattered new bone tissue. In the mild demineralized group, a small amount of particles remained and were surrounded by new bone. In the moderate demineralized group, there were some residual dentin particles and bone cells arranged in regular order. In the severe demineralized group, there was no residual dentin granule and bone cells were mature and arranged regularly. In the blank control group, the trabeculae in alveolar socket were arranged disorderly and bone marrow cavity was filled with abundant fibrous connective tissue. (4) It is concluded that autogenous dentin particles with different degrees of demineralization possess the potential to guide new bone formation in alveolar bone preservation. The dentin particles that are demineralized for 10 minutes demonstrated the best effects on promoting bone regeneration. 

Key words: bone, implant site preservation, dentin particle, bone graft, bone regeneration, animal experiment