Periodontal tissue regeneration on the surface of synthetic hydroxyapatite implanted into root surface

Several studies have demonstrated that periodontal ligament (PDL)-derived cells can form a new connective tissue attachment (NCTA) not only on denuded dentin but also on nondental inorganic materials. Although the cellular response to these materials may be different than that to denuded dentin, the process of NCTA formation on the surface of non-dental inorganic materials is still undetermined. In the present study, we compared the process of NCTA formation on the surface of an inorganic material with that on a denuded root surface by implanting a block of synthetic hydroxyapatite (HA) into a root cavity prepared on the first molar of a rat. We then observed tissue regeneration under conditions where the PDL-derived cells could populate the HA surface using an occlusive membrane. After fibrinous exudation at 3 days postoperatively, granulation tissue from the PDL filled the space between the HA block and the membrane at 1 week. Four weeks after the operation, although the granulation tissue increased in density at the interface to the HA block, no obvious deposition of cementum-like tissue was seen on the HA block. Six weeks after the operation, the deposition of cementum was observed on the surface of the HA block. The deposition of cementum became more extensive and insertion of collagen fibers into the cementum layer became more obvious 8 weeks postoperatively. Twelve weeks after the operation, the cementum covered almost the entire surface of the HA block. On the surface of the denuded dentin in control teeth, cementum deposition was seen at 4 weeks after the operation and increased in thickness from 6 weeks on.(ABSTRACT TRUNCATED AT 250 WORDS)