Hiroyasu Takeuchi

In vivo study of a calcium phosphate cement consisting of α-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide

Prehardened calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted in rabbit mandibles and back muscles, and studied histologically and microradiographically. In the mandibles, new bone formation occurred around the implants and increased in quantity the longer the implant period lasted. Histology, microradiography and scanning electron microscopy (SEM) demonstrated direct contact of bone and cement. Bone response to this cement was essentially the same as to hydroxyapatite (HA) ceramics, known as a biocompatible bone substitute. Material resorption was recognized, which increased with the implant period and was greater in the surface bound by soft tissue than the surface bound by bone tissue. In the back muscles, however, no calcified tissue formation occurred. Resorption proved to be faster than in the case of the mandible implants. It was concluded that the cement, in prehardened form, has good biocompatibility and is a promising material as a bone substitute.

Histological and microradiographic evaluation of hydrated and hardened α-tricalcium phosphate/calcium phosphate dibasic mixtures

Bone tissue response to pre-hardened alpha-tricalcium phosphate (alpha-TCP) and calcium phosphate dibasic (DCPD) mixture by hydration was studied histologically and microradiographically after implanting on the inferior aspect of the mandible in rabbits. In 1-month implants, new bone formation was observed along the surface of the material near the host bone, and connection of new and host bone through thin bone bridges was seen in some places. In 3-month implants, newly formed bone filled the greater part of the gap between material and host bone, and in 6-month implants, it surrounded almost all the surface of the material. New bone was in direct contact with the material in all implant periods. The bone response was essentially consistent with that to hydroxyapatite (HA). Resorption of the material was noticed in 3- and 6-month implants. It was concluded that pre-hardened alpha-TCP/DCPD mixture has good biocompatibility with bone tissue equal to HA and that it resorbs when implanted in rabbit. Further research should be performed to evaluate the material changes of resorption and formation of the white zone.