Histomorphometric and mineral degradation study of Ossceram: a novel biphasic B-tricalcium phosphate, in critical size defects in rabbits

Objective: To carry out a histomorphometric analysis of a new highly porous (95%) biphasic calcium phosphate (hydroxyapatite 60%/B‐tricalcium phosphate 40%), used to fill critical size defects in rabbit tibiae, supplementing histomorphometric findings with radiographic thermal imaging, EDX analysis and Ca/P ratio mapping at different time stages. Materials and methods: Two critical size defects of 6 mm diameter were created in both tibiae of 21 New Zealand rabbits, test group (Ossceram^®) and control group. Histomorphometric, radiographic thermal imaging, EDX and element mapping analysis were performed at 15, 30 and 60 days after graft insertion. Results: Histomorphometric analysis at 30 days showed more new bone formation in defects filled with Ossceram^® 4.41 ± 0.23 mm than the test group 1.94 ± 0. 28 mm (P<0.05). Element analysis revealed higher percentages of Ca (42.33 ± 2.8%) and P (1.3 ± 0.8%) in the test group than in the control group (P<0.05). Element mapping showed that Ca and P were concentrated in medullar and cortical zones in the test group but were concentrated only in cortical zones in the control group. Test group histomorphometry at 60 days showed complete closure of the cortical defect 5.37 ± 0.32 mm more than the control group 2.3 ± 0.54 mm. There was no cortical defect closure or medullar bone formation in the control group (P<0.05). Element analysis revealed higher percentages of Ca (32.26 ± 21.7%) and P (1.5 ± 0.3%) in the test group than in the control group (P<0.05). Conclusion: Defects of a critical size in a rabbit tibia model can be sealed using a highly porous biphasic calcium phosphate; this supports new bone formation, creates a bridge between borders and facilitates bone ingrowth. Furthermore, this study observed partial dissolution of the mineral phase of the graft material and its incorporation into the surrounding bone. Radiographic thermal imaging may be used to supplement histological and chemical analyses.