The Current Situation of Carbonate Apatite as a Noble Bone Substitute and Its Future Development in the Oral Region

Abstract

Bone apatite is not hydroxyapatite, but carbonate apatite (CO₃Ap), which contains 6-9 wt% carbonate in its apatitic structure. Hydroxyapatite is not resorbed in the body but CO₃Ap can be resorbed and replaced with bone. Therefore, CO₃Ap has the potential to be an ideal artificial bone substitute. We have succeeded in fabricating chemically pure low crystalline CO₃Ap through a dissolution-precipitation reaction using precursors, such as calcium carbonate, dicalcium phosphate dihydrate, and calcium sulfate, without sintering. Some animal experiments revealed that the fabricated CO₃Ap was resorbed by osteoclasts and replaced with new bone similar to an autogenous bone graft, and it also exhibited high osteoconductivity.

In Japan, there was no artificial bone substitute allowed for use adjacent to dental implants. Based on clinical trials for sinus floor augmentation, granular-type CO₃Ap was approved as an artificial bone substitute that can be used in all dental fields, including those adjacent to dental implants, as Cytrans^® Granules (GC Corp., Tokyo, Japan).

This comprehensive review introduces clinical cases of sinus floor augmentation, reconstruction of bone defects after cystectomy of the jaw and alveolar ridge augmentation by using Cytrans^® and instructions and directions for its clinical use. Furthermore, we have succeeded in fabricating porous CO₃Ap. The porous CO₃Ap was useful for reconstructing a rabbit mandibular bone defect model and could also be an excellent candidate for a scaffold in bone regenerative medicine because it has higher osteoconductivity and is replaced with bone.