Materials and Methods: Fifteen adult rabbits were allocated to the study. Four holes were created in the calvarial bone. Holes 1-4 were filled as described below: hole 1 was right unfilled and kept as control; hole 2 was filled with nano bone; hole 3 was filled using an autogenous bone; and hole 4 was filled with a mixture of nano-capsules containing risedronate. At 4, 8 and 12 weeks after surgery, blood samples were obtained and red blood cell, white blood cell, hemoglobin, hematocrit, mean cell volume, mean cell HGB and platelet counts were determined. Then animals were scarified and bone density was determined using radiography images.

Results: Bone formation in nano risedronate + autograft and autograft were 0.31 ± 0.03 and 0.25 ± 0.02, respectively, while in nano risedronate and control groups were 0.11 ± 0.01 and 0.08 ± 0.02, respectively (P < 0.05). Significant differences were observed in bone density in nano risedronate + autograft as 0.37 ± 0.01, while the density in the autograft, nano risedronate, and control groups were as 0.32 ± 0.01, 0.14 ± 0.01, and 0.09 ± 0.02, respectively (P < 0.05). Bone density after 12 weeks were 0.51 ± 0.01, 0.36 ± 0.02, 0.21±0.01, and 0.19 ± 0.02 in nano risedronate + autograft, nano risedronate, autograft, and control groups, respectively (P < 0.05). In all stages of the study, the nano risedronate + autograft group had better bone formation in comparison to the other groups (P < 0.05). Different filling materials of defects had no effect on blood hematology indexes (P > 0.05).

Conclusion: These results suggest nano risedronate + autograft has positive effects on calvarial bone defects healing in rabbit.