The resistance of macroporous calcium phosphate ceramics to compressive strength generally is low and depends on, among other factors, porosity percentage and pore size. A compromise always is adopted between high porosity, required for a good integration, and mechanical strength, which increases with material density. We improved the strength of macroporous calcium phosphate ceramics of interconnected porosity by filling the pores with a highly soluble, self-setting calcium phosphate cement made of TCP and DCPD. Cylinders of the resulting material were implanted in sheep condyles and subjected to histological analysis after 20, 60, and 120 days. Microradiographs were made of the histological sections. The control material consisted of ceramic that had not been loaded with cement. Progressive ingrowth of bone into the ceramic pores occurred as the cement was degraded during the first implantation period. Marked degradation of the cement was apparent after 2 months, with fragmentation of the cement in most of the pores and the presence of bone tissue between the fragments. All the cement had been replaced by bone after 4 months. Some fragments of cement still were embedded in the newly formed bone. There was no significant difference between the integration of loaded and nonloaded ceramics. Filling the macroporous ceramic pores with a calcium phosphate cement significantly improved the mechanical strength of these ceramics without modifying their integration in the healing bone.

Calcium phosphate cements are able to set in situ when injected into bone tissue. We evaluated the tissue reaction occurring when a DCPD-based calcium phosphate cement was either set within the bone or implanted when already set. The samples were implanted in rabbit condyles and examined histologically after 8 and 16 weeks. The relative bone surface, the fibrous capsule around the implants and the implant section surface were measured. Solid material seemed to be better tolerated than paste implants. More bone was found at the solid implant contact whatever the implantation time and the solid material degraded much less rapidly. In conclusion, the physico-chemical modification of the biological environment occurring during setting increases the foreign body reaction against the material.

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