Micro-CT Analysis of Bone Healing in Rabbit Calvarial Critical-Sized Defects with Solid Bioactive Glass, Tricalcium Phosphate Granules or Autogenous Bone

Abstract

Objectives: The purpose of the present study was to evaluate bone healing in rabbit critical-sized calvarial defects using two different synthetic scaffold materials, solid biodegradable bioactive glass and tricalcium phosphate granules alongside solid and particulated autogenous bone grafts.

Material and methods: Bilateral full thickness critical-sized calvarial defects were created in 15 New Zealand white adult male rabbits. Ten defects were filled with solid scaffolds made of bioactive glass or with porous tricalcium phosphate granules. The healing of the biomaterial-filled defects was compared at the 6 week time point to the healing of autologous bone grafted defects filled with a solid cranial bone block in 5 defects and with particulated bone combined with fibrin glue in 10 defects. In 5 animals one defect was left unfilled as a negative control. Micro-computed tomography (micro-CT) was used to analyze healing of the defects.

Results: Micro-CT analysis revealed that defects filled with tricalcium phosphate granules showed new bone formation in the order of 3.89 (SD 1.17)% whereas defects treated with solid bioactive glass scaffolds showed 0.21 (SD 0.16)%, new bone formation. In the empty negative control defects there was an average new bone formation of 21.8 (SD 23.7)%.

Conclusions: According to findings in this study, tricalcium phosphate granules have osteogenic potential superior to bioactive glass, though both particulated bone with fibrin glue and solid bone block were superior defect filling materials.

Keywords: bone regeneration; bone substitutes; bone transplantation; skull.

Figure 1

A = Empty negative control defect showing a minimum of healing with uneven, centric ingrowth from the margins of the defect (arrows) and small bone islets in the center of the defect (arrowhead). Mature intact calvarial bone marked with asterisk. B = Defect filled with combination of particulated autogenous bone (yellow and orange granules inside of dotted circle) and fibrin glue (dark red areas pointed with arrowhead). Mature intact calvarial bone marked with asterisk. C = Defect with autologous bone block. The margins of the bone block have been partially resorbed (long arrow) and partial osseous continuity of the margin the bone block can be seen (inside of dotted circle). Mature intact calvarial bone marked with asterisk. D = Resorbable BAG scaffold in defect (dark red). Ingrowth of new bone from the defect margin can be seen as well as very small ossifying spots in the middle of scaffold material (yellow/orange spots inside of dotted circle). Mature intact calvarial bone marked with asterisk. E = TCP granules (blue spots pointed with arrowheads) filling a calvarial defect. Bone formation on the material surfaces can be seen (yellow and orange spots pointed with arrows). Mature intact calvarial bone marked with asterisk.