PURPOSE: To compare the mechanical strength of surgically created and healed rat calvarial defects having been filled with three different osteopromotive substances: hydroxyapatite, intramembraneous demineralised bone matrix (DBM), and autogenous bone chips. MATERIAL: Sixty adult male Wistar rats were divided into three groups of 20 animals, each group representing healing times of one, three, or six months. METHODS: Identical 5mm bilateral critical size defects were trephined into the parietal bones and hydroxyapatite, DBM, or autogenous bone chips were implanted into the defects, or left as unfilled controls. The repaired defects were evaluated biomechanically using a modified punch out test 1, 3, or 6 months postoperatively. RESULTS: The maximum load carried in the DBM group was significantly higher than in the bone chips, hydroxyapatite, and control groups after one month of healing. The mean bone strength did not increase significantly after the first month of healing in any of the groups. The DBM group showed a significantly higher load to failure than the other groups at all three observation periods. The mean maximum load to failure of the bone chips and hydroxyapatite groups was slightly higher than in the control group; however the difference was not statistically significant. None of the control experimental bone defects demonstrated any bone formation. CONCLUSION: Defects filled with hydroxyapatite and bone chips were not significantly stronger than unfilled controls, whereas defects filled with DBM were significantly stronger than all other defects after 1, 3, and 6 months of healing.
PURPOSE: To compare the mechanical strength of surgically created and healed rat calvarial defects having been filled with three different osteopromotive substances: hydroxyapatite, intramembraneous demineralised bone matrix (DBM), and autogenous bone chips. MATERIAL: Sixty adult male Wistar rats were divided into three groups of 20 animals, each group representing healing times of one, three, or six months. METHODS: Identical 5mm bilateral critical size defects were trephined into the parietal bones and hydroxyapatite, DBM, or autogenous bone chips were implanted into the defects, or left as unfilled controls. The repaired defects were evaluated biomechanically using a modified punch out test 1, 3, or 6 months postoperatively. RESULTS: The maximum load carried in the DBM group was significantly higher than in the bone chips, hydroxyapatite, and control groups after one month of healing. The mean bone strength did not increase significantly after the first month of healing in any of the groups. The DBM group showed a significantly higher load to failure than the other groups at all three observation periods. The mean maximum load to failure of the bone chips and hydroxyapatite groups was slightly higher than in the control group; however the difference was not statistically significant. None of the control experimental bone defects demonstrated any bone formation. CONCLUSION: Defects filled with hydroxyapatite and bone chips were not significantly stronger than unfilled controls, whereas defects filled with DBM were significantly stronger than all other defects after 1, 3, and 6 months of healing.