Osteopromotive Property of Allogenic Demineralized Dentin Matrix

The objective of this study was to evaluate the osteopromotive property of allogenic demineralized dentin matrix (allogenic DDM) using a rabbit model of surgical bone defect. Alveolar bone deficiency is a major problem in the treatment of traumatic injuries, periodontal diseases, tumor resections, and also in some cosmetic/constructive surgeries. Orthopedics and dentistry are the major fields of medicine dealing with bone deficiency and bone grafts. There are different kinds of grafts and biomaterials being used for bone regeneration that are neither cost effective nor free of complications. Therefore, introducing an improved and feasible bone regenerative material is of great importance. Although DDM as an autograft has been shown to accelerate bone regeneration, it may not be practical in certain cases. In order to obtain the autogenous DDM, one needs to sacrifice his/her own healthy tooth to rebuild bone, and obviously this is not possible in edentulous patients. To overcome this concern, it is best to utilize teeth that are extracted from other individuals (due to orthodontic treatments or wisdom teeth extractions, which are routinely discarded) to make an appropriate bone regenerative material, allogenic DDM. Based on our preliminary observations of the bone regenerative abilities of allogenic DDM, we hypothesized that allogenic DDM has bone regenerative properties. To test our hypothesis, in the present study we used rabbit model for evaluating the extent to which allogenic DDM increases bone formation and improves the quality of the newly-formed bone. We also examined if implementation of allogenic DDM causes inflammatory reaction and/or infection. The allogenic DDM specimens were prepared using the mandibular incisors of rabbits. Surgical bone defects were created on the skull of 30 New Zealand White rabbits (two defects in each rabbit). Experimental defects in 24 rabbits were filled with allogenic DDM applying the guided bone regeneration technique with the use of collagen absorbable membrane. In the control defects, both inner and outer surfaces were covered by membrane with no material in between. However, in the remaining six rabbits, both defects were left empty and these rabbits served as control for blood biomarkers. The 24 experimental rabbits were divided into four groups and sacrificed after 15, 30, 60, and 90 days (n=6 at each time-point). The thickness of bone samples was measured at the center of the specimens before utilizing for micro-computed tomography ('CT) in order to assess their microstructural properties. Blood samples were collected from all rabbits at the baseline, 48 hours postsurgery and at each time-point for measuring catabolic and anabolic factors critical in bone regeneration. Bone thickness was significantly higher in experimental group at all time-points. Moreover, microstructural properties showed superior bone quality in experimental group. At all time-points except for 48 hours postsurgery, white blood cell count was numerically higher in control rabbits compared to experimental rabbits ruling out any inflammation or infection due to allogenic DDM. Bone specific alkaline phosphatase (BAP) activities were lower in both experimental and control groups at all time-points in comparison to baseline values for which we cannot offer an explanation. The lower BAP activity is usually indicative of either lower rate of bone formation or bone turnover. The results of the present study indicate that allogenic DDM significantly improves both bone quantity and quality through its osteoinductive and osteoconductive properties.