An animal study on the bone behaviour of Ca-P-coated implants: influence of implant location.

Four different implant materials were installed into the mandibular corner of goats to investigate the trabecular bone response in a mainly unloaded model. The implants were installed using a standardized technique and were left in situ for 12 weeks. One goat had to be sacrificed after surgery because of a broken rib; the other animals healed uneventfully. After sacrifice of the animals, the bone response to the uncoated and the three different Ca-P implants was evaluated histologically and histomorphometrically. Four sections of each implant were evaluated; two were located in the cortical and two in the trabecular bone. Of the 44 retrieved implants, 20 implants appeared to be installed partially in the mandibular canal, as clearly visible on the X-rays. These implants were not used in the histomorphometrical measurements. Histological evaluation showed that the trabecular and cortical bone reactions were similar; there was no significant difference in the percentage of bone contact nor in the amount of bone in contact with the implants. In conclusion this study showed that the mandibular corner is an unsatisfactory model for the installation of implants because of anatomical restrictions. Also, the experiment remained inconclusive about the influence of loading conditions on bone behaviour. Nevertheless, the histological results confirmed the bioactive properties of Ca-P coatings.