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Background and purpose: This study was designed to identify the cells involved in the healing of the parietal bone defects after implantation of octacalcium phosphate (OCP) combined with bone matrix gelatin (BMG).
Materials and Methods: Sixteen young male Sprague Dawley rats (5-6 weeks age) were used. A full thickness standardized trephine defects, 5mm in diameter, was made in the rat parietal bone and OCP combined with BMG (in ¼ ratio) was implanted into the defect. No OCP/BMG particles were implanted in control group that was otherwise treated identically. Cellular identification was carried out on days 7th and 14th after implantation, by light and transmission electron microscopy.
Results: Ultrastractural identification of cells involved in the healing of the defects in experimental group on day 7th after implantation, showed full secretory chondroblasts and also showed the integration of newly formed matrix with the defect margins. On day 14th after implantation the results revealed the typical osteoblasts that are active in the defect margins.
Conclusion: In experimental group, bone defects were healed through intramembranous ossification route.

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Background and purpose: Reconstruction of bone defects remains one of the most challenges encountered by orthopedic and reparative surgeons. The purpose of this study was to assess the osteogenic potential of octacalcium phosphate (OCP) and octacalcium phosphate/gelatin (OCP/G) composite in the tibia bone defects in rats.

Materials and methods: This experimental study was conducted in 72 male Sprague Dawley rats. The rats were divided into experimental (OCP/G and OCP) and control groups (n=24 per group). Full thickness critical size trephine defects were made in the rat's tibial bones and filled with 6 mg of OCP and OCP/G composite in experimental groups. The control group had no intervention. On days 7, 14, 21 and, 56 after implantation, the rats were decapitated and bone samples were collected. Then, 5µm thick sections were cut and stained with H&E. Finally, the amount of newly formed bone was measured using Dunnett T3 test.

Results: In experimental groups, the new bone formation was initiated at the defect margins in day 7 after implantation. During the remaining days, in addition to bone formation in deep parts of the defect, the newly formed bones were found to be more mature. In the control group, the newly formed bones were seen near to the defect margins. There were significant differences in the amount of newly formed bone between the experimental and control groups (P<0.001).

Conclusion: This biomaterial could be used in the repair of long bone defects in clinical situations.