Experimental Study of Implanted Porous Hydroxyapatite Particles in Fresh Extracted Sockets for Maintaining Pontic/tissue Relationships in Dogs

In this study, porous hydroxyapatite particles (HAP) were implanted in the fresh extracted sockets in order to demonstrate whether an adequate pontic/tissue relationships for fixed partial denture could be achieved. Right and left maxillary second incisors were extracted separately in 6 mongrel dogs. HAP were inserted in the right postextracted sockets. The other site was left to heal without HAP insertion and served as the control. Three months later a three-unit fixed partial denture was placed individually on both sites. The 4th and the 6th months after operation, both sites were examined by macroscope, radiography and histopathology methods. The results were as follows: 1. In all of the dogs after 3 months, ridge of the implanted site presented a rounded contour whereas the contralateral ridge atrophied into a knife-edge shape characteristically. 2. Healthy ridge and proper relationship of pontic/tissue were obtained in the implanted site after fixed partial denture was setted. On the other hand, plaque accumulation and marginal gingivitis increased gradually in the unimplanted site due to poor pontic/tissue relationship. 3. In the implanted site, new bone formation was observed around and between HAP, it increased still further and consisted with matured structure of lamellar bones. 4. In the unimplanted site, the newly formed bone became thinner and shorter gradually because of the reconstruction of bone tissue.