Guided bone regeneration in standardized calvarial defects using beta-tricalcium phosphate and collagen membrane: a real-time in vivo micro-computed tomographic experiment in rats

Guided bone regeneration (GBR) procedures using graft materials have been used for reconstruction of osseous defects. The aim of the present in vivo micro-computed tomographic (A mu CT) and histologic study was to assess in real time the bone regeneration at GBR sites in standardized experimental calvarial defects (diameter 3.3 mm) using beta-tricalcium phosphate (beta-TCP) with and without collagen membrane (CM). A single full-thickness calvarial defect was created on the left parietal bone in young female Wistar albino rats (n = 30) weighing approximately 300 g and aged about 6 weeks. The animals were randomly divided into three groups for treatment, based on calvarial defect filling material: (1) control group (n = 10); (2) beta-TCP + CM group (n = 10); (3) beta-TCP group (n = 10). Real-time in vivo A mu CT analyses were performed immediately after surgery and at 2, 4, 6 and 10 weeks to determine the volume and mineral density of the newly formed bone (BVNFB, MDNFB) and remaining beta-TCP particles (VRBP, MDRBP). The animals were killed at 10 weeks and calvarial specimens were evaluated histologically. In the control group, MDNFB increased significantly at 6 weeks (0.32 +/- A 0.002 g/mm(3), P < 0.01) compared to that at baseline. In beta-TCP + CM group, BVNFB (1.10 +/- A 0.12 mm(3), P < 0.01) and MDNFB (0.13 +/- A 0.02 g/mm(3), P < 0.01) significantly increased at the 4th week than baseline. In the beta-TCP group, BVNFB (1.13 +/- A 0.12 mm(3), P < 0.01) and MDNFB (0.14 +/- A 0.01 g/mm(3), P < 0.01) significantly increased at 6 weeks compared to that at baseline. Significant reduction in VRBP was neither seen in the beta-TCP + CM group nor in the beta-TCP group. While in the beta-TCP + CM group MDRBP was reduced significantly at 6 weeks (0.44 +/- A 0.9 g/mm(3), P < 0.01) from baseline (0.98 +/- A 0.03 g/mm(3)), similar significant reduction in MDRBP from baseline (0.92 +/- A 0.07 g/mm(3)) was seen only at 10 weeks (0.45 +/- A 0.06 g/mm(3), P < 0.05) in the beta-TCP group. Histologic findings at 10 weeks revealed greater amount of NFB with osteocytes in the matrix, in the beta-TCP + CM group than in the beta-TCP group. Biomechanical assessment of NFB for hardness (H) and elastic modulus (E) revealed significantly higher values for the beta-TCP + CM group (H = 612.6 +/- A 4.28 Mpa; E = 13.57 +/- A 0.07 Gpa) when compared to those of the control (H = 192.1 +/- A 4.93 Mpa; E = 6.76 +/- A 0.04 Gpa) and the beta-TCP groups (H = 241.9 +/- A 6.29 Mpa; E = 4.34 +/- A 0.06 Gpa). In conclusion, based on real-time assessment, NFB is formed in calvarial defects as early as 4 weeks following GBR with beta-TCP + CM as compared to 6 weeks when beta-TCP alone was used.