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Since bone apatite is a carbonate apatite containing carbonate in an apatitic structure, carbonate content may be one of the factors governing the osteoconductivity of apatitic bone substitutes. The aim of this study was to evaluate the effects of carbonate content on the osteoconductivity of apatitic bone substitutes using three commercially available bone substitutes for the reconstruction of alveolar bone defects of a beagle mandible with simultaneous dental implant installation. NEOBONE, Bio-Oss, and Cytrans that contain 0.1, 5.5, and 12.0 mass% of carbonate, respectively, were used in this study. The amount of newly formed bone in the upper portion of the alveolar bone defect of the beagle's mandible was 0.7, 6.6, and 39.4% at 4 weeks after surgery and 4.7, 39.5, and 75.2% at 12 weeks after surgery for NEOBONE, Bio-Oss, and Cytrans, respectively. The results indicate that bone-to-implant contact ratio was the largest for Cytrans. Additionally, the continuity of the alveolar ridge was restored in the case of Cytrans, whereas the continuity of the alveolar ridge was not sufficient when using NEOBONE and Bio-Oss. Both Cytrans and Bio-Oss that have a relatively larger carbonate content in their apatitic structure was resorbed with time. We concluded that carbonate content is one of important factors governing the osteoconductivity of apatitic bone substitutes., (© 2019 Wiley Periodicals, Inc.)

Carbonate apatite (CO 3 Ap) granules are known to show good osteoconductivity and replaced to new bone. On the other hand, it is well known that a porous structure allows bone tissue to penetrate its pores, and the optimal pore size for bone ingrowth is dependent on the composition and structure of the scaffold material. Therefore, the aim of this study was to fabricate various porous CO 3 Ap granules through a two-step dissolution-precipitation reaction using CaSO 4 as a precursor and 30-, 50-, 120-, and 205-μm diameter microfibers as porogen and to find the optimal pore size of CO 3 Ap. Porous CO 3 Ap granules were successfully fabricated with pore size 8.2-18.7% smaller than the size of the original fiber porogen. Two weeks after the reconstruction of rabbit calvarial bone defects using porous CO 3 Ap granules, the largest amount of mature bone was seen to be formed inside the pores of CO 3 Ap (120) [porous CO 3 Ap granules made using 120-μm microfiber] followed by CO 3 Ap (50) and CO 3 Ap (30). At 4 and 8 weeks, no statistically significant difference was observed based on the pore size, even though largest amount of mature bone was formed in case of CO 3 Ap (120). It is concluded, therefore, that the optimal pore size of the CO 3 Ap is that of CO 3 Ap (120), which is 85 μm., (© 2019 Wiley Periodicals, Inc.)

Carbonate apatite (CO 3 Ap) is an inorganic component of bone. This study aimed to compare the composition and tissue response to of CO 3 Ap (CO 3 Ap-DP) fabricated by the dissolution-precipitation reaction using calcite as a precursor and Bio-Oss®, which is widely used in orthopedic and dental fields as a synthetic bone substitute. X-ray diffraction and Fourier transform infrared results showed that CO 3 Ap-DP and Bio-Oss® were both B-type carbonate apatite with low crystallinity. The average sizes of CO 3 Ap-DP and Bio-Oss® granules were 450 ± 58 and 667 ± 168μ m, respectively, and their carbonate contents were 12.1 ± 0.6 and 5.6 ± 0.1 wt%, respectively. CO 3 Ap-DP had a larger amount of CO 3 than Bio-Oss® but higher crystallinity than Bio-Oss®. When a bone defect made at the femur of rabbits was reconstructed with CO 3 Ap-DP and Bio-Oss®, CO 3 Ap-DP granules were partially replaced with bone, whereas Bio-Oss® remained at 8 weeks after implantation. CO 3 Ap-DP granules elicited a significantly larger amount of new bone formation at the cortical bone portion than Bio-Oss® at 4 weeks after the implantation. The results obtained in the present study demonstrated that CO 3 Ap-DP and Bio-Oss® showed different behavior even though they were both classified as CO 3 Ap. The CO 3 content in CO 3 Ap played a more important role than the crystallinity of CO 3 Ap for replacement to bone and high osteoconductivity.