Progressive resorption of the alveolar ridge after tooth extraction results in diminished retention and stability of a denture. Preprosthetic augumentation of the alveolar ridge is therefore required to provide a firm base for a denture and reconstruct the functional occlusion in the field of oral and maxillofacial surgery.
Octacalcium phosphate (OCP), the putative precursor of biological hydroxyapatite, was implanted into the subperiosteal pocket adjacent to the mandibular alveolar ridge in 7-week-old male Wistar rats. Soft radiographic and the histological examinations were performed to investigate the biological response to the OCP implant and assess possibilities for the clinical application.
OCP was prepared using the method of LeGeros; granules between 32 and 48 mesh were used for implantation. Four rats were used in each experimental group. The animals were perfused with 4% paraformaldehyde in 0.1 M phosphate buffer at pH 7.4. After soft radiographic examination, the specimens were decalcified in a mixed solution of sodium citrate and formic acid, embedded in paraffin, sliced into thin sections, and stained with hematoxylin and eosin.
In the experimental group, signs of radiopacity were not obvious at the implantation site at one week. At two weeks, increased signs of radiopacity were noted at the implantation site. The radiopacity increased markedly by four weeks after implantation and seemed to be relatively homogeneous, well amalgamated to the contiguous bone. Bone resorption was not obvious at the implantation site after eight weeks.
Histologically, the implanted-OCP (i-OCP) was stained by hematoxylin at one week. The ridge was augumented at the region corresponding to the implantation site. Numerous connective tissue cells and inflammatory cells were surrounding i-OCP. Additional bone formation increased with time. I-OCP tended to aggregate and be resorbed. Two weeks after implantation, inflammatory cells decreased. After four weeks, i-OCP was surrounded by new bone. The newly formed bone was observed to mature with time and was not resorbed after eight weeks. The present study suggested that OCP is a useful material to augument the atrophic alveolar ridge in preprosthetic surgery.