Fabrication and histological evaluation of bone-replacing calcium phosphate cement using NaHCOィイD23ィエD2

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Alternation of a composition of set apatite cement (AC) from carbonate-free apatite (CO3-free AP) to carbonate apatite (CO3-AP) may accelerate replacement of the set AC with bone since CO3-AP can be dissolved much faster than CO3-free AP in the weak acidic solution produced by osteoclast. In this investigation, NaHCO3 was added to the AC component and the effects of added NaHCO3 on cement setting behavior and on set mass were studied as an initial step for the fabrication of AC which can be replaced with bone faster than current AC. When NaHCO3 was added to AC, the resultant set mass contained CO3. Although not all CO3 was incorporated in the set AC, the amount of CO3 incorporated into the set AC increased with the amount of added NaHCO3. FT-IR measurement revealed the formation of B-type CO3-AP. The setting time was prolonged from 30 min to 45 min, indicating that NaHCO3 has an inhibitory effect on AP formation. The diametral tensile strength (DTS) of the set AC decreased significantly with the addition of NaHCO3. Scanning electron microscopic observation revealed that fine crystals were formed in the set AC when NaHCO3 was added to AC. As a result, the crystallinity indexes of the set AC measured using powder x-ray diffraction (XRD) and FT-IR decreased with an increase in the amount of added NaHCO3. The dissolution rate of set AC in weak acid, pH 5.5, increased with the amount of added NaHCO3. The number of resorption pits and the resorbed area by cultured osteoclasts increased according to added CO3 content. The resorbed area on 4% CO3 containing-AC was twice as much as carbonate-free AC. The results suggested that CO3-AP-formed AC would be easily resorbed by osteoclasts and have good potential value for its use in wider clinical applications in oral and maxillofacial, plastic and reconstructive surgery.