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Tissue response to a readily consolidating material prepared by mixing α-tricalcium phosphate (α-TCP) powder with a glycolic acid dextran solution and to this consolidating material combined with particulate hydroxylapatite (HA) was studied after implantation in the subperiosteal space of the mandible in rabbits. Active new bone formation comparable to that seen on HA implants was observed around the two compounds. The newly formed bone was in direct contact with the HA as well as the readily consolidated material and little adverse effect resulting from the glycolic acid and dextran was observed. Because the readily consolidating material was firm and could be countoured into any shape during the process of consolidation, it may be quite useful as a bone substitute and as an adherent for HA particles for reconstructive bone surgery, overcoming the disadvantages inherent to the particulate form of HA.

Tissue response to preformed tricalcium phosphate (TCP) blocks prepared from alpha-tricalcium phosphate (alpha-TCP) powder by hydration and hardening at 80 degrees C was studied by implanting them subperiosteally on the buccal aspect of the mandible in rabbits. X-ray diffraction of the alpha-TCP powder showed a typical pattern of TCP, whereas a mixed pattern of TCP and hydroxylapatite was obtained after hydration and hardening. The radiographic findings at 4 weeks showed a tendency to bony union of the TCP block with the underlying bone. Microscopically, new bone that was being formed extensively from the underlying bone surface and filling the space between the block and bone at 4 weeks gradually changed into lamellar bone. There was no evidence of resorption of the TCP block throughout the experiment. The tissue response was essentially consistent with that to hydroxylapatite particles studied under similar conditions in our laboratory. It was concluded that the hydration and hardening of alpha-TCP powder may provide an implant block with a desirable contour that does not interfere with bone formation.