Histological study of the unsintered carbonate containing apatite porous body in beagle dog dorsal muscle

Bone apatite is not composed of pure hydroxyapatite (HAp), but contains calcium, phosphoric acid, hydroxyl groups and is substituted with many ions. The difference between bone apatite and HAp is the absence of carbonate ions in HAp. Recently, synthetic carbonated apatite (sCA) has been proposed as a substitute bone material, showing both excellent biocompatibility and bioabsorbability. Recently, we have newly developed and reported unsintered carbonate-containing apatite (usCA), which is synthesized from dibasic calcium phosphate dihydrate (DCPD). In this study, we investigated the histological changes in usCA containing tissue following implantation in the dorsal muscle of beagle dogs in comparison with sCA and β-tricalcium phosphate (TCP). Eighteen male beagle dogs received an incision in three vertical positions, and the experimental materials were embedded in an envelope formed in the dorsal muscle. Each sample was photographed using a micro computed tomography (μCT) analyzer. Following removal of the samples, tissue sections were stained with hematoxylin and eosin, alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP). Analysis with μCT showed that the usCA group showed a significantly higher absorption rate than the sCA and β-TCP groups at 3 and 6 months. usCA showed superior tissue compatibility, ectopic bone formation and absorbability. Thus, this material appears to be suited for clinical applications