DEPROTEINIZED BOVINE BONE GRAFT REMODELING PATTERN IN ALVEOLAR SOCKET. HISTOLOGIC AND IMMUNOHISTOLOGICAL EXPRESSION EVALUATION.

Deproteinized bovine bone (DBB) is a bone graft highly used in dentistry in bone regeneration and alveolar socket preservation techniques. Although there is a scientific consensus on the clinical benefit of this biomaterial, and several in vitro studies described its biologic effect on osteoblasts, in vivo analyses investigating its effect on bone dynamics on human are lacking. For this purpose 20 patients needing tooth extraction and implant placement were selected and randomized in test (alveolar socket preservation with DBB) and control (spontaneous healing). Bone specimens were collected during tooth extraction (T0) and, at 5 months, during implant placement (T1). The collected samples were processed for histologic and immunohistological analyses to reveal the presence of positive (BMP-2, BMP-7, ALP) and negative (Il-6, TNF-α) markers of bone remodeling. The sections were then micro-photographed, quantification was done and statistical analyses were performed to compare T0 and T1 in both groups and T1 test group versus T1 control group. The obtained results showed higher expression of BMP-2, BMP-7 and IL-6 at T1 in both groups (p<0.05), lower expression of ALP in both (p<0.05) at T1 and higher expression of TNF-α only in test group (p<0.05) while in control group it remained stable during time. When comparing T1 markers expression in control and test groups, a higher expression of BMP-2 (p<0.05) and lower expression of TNF-α (p<0.05) were found in the first one. These results are in concordance with the previous in vitro studies and show that DBB is able to maintain bone remodeling in active phases. As a matter of fact at 5 months a higher expression of the positive markers (BMP-2, BMP-7) was noticed compared to T0, but the presence of DBB resulted in lower expression of BMP-2 and higher expression of inflammatory factor (TNF-α) when comparing to spontaneous healing at the time of the implant placement. 
For these reasons the use of DBB is suggested when clinical needs lead to a precise indication of alveolar socket preservation with biomaterial, while, if not clinically necessary, spontaneous healing is indicated because it shows more biological positive effects.