Cementum formation around a titanium implant: a case report.

Animal studies have shown that a periodontal ligament may be produced around a titanium implant when it is in contact with fractured and retained roots. Formation of cementum and attachment connective tissue around titanium implants confirms that cementum progenitor cells are located in the periodontal ligament, since cementum and periodontal ligament are present at the implant-root interface, whereas the remainder of the implant, which is not in contact with the root, shows osseointegration. The aim was to evaluate histologically the characteristics of the tissue present between a titanium implant and a retained root, which were subsequently extracted as a result of peri-implantitis. The histologic examination revealed a continuous layer of cementum and numerous cementocytes on the implant surface. No blood vessel or collagen fibers were detected in the periodontal space. In contrast to experimental studies carried out on animals, the lack of connective tissue fibers and the presence of hypercementosis in this specimen could have been caused by the inflammatory process. Furthermore, the extrusive movement of the root might explain the presence of cementum hypertrophy. Further studies are required to establish whether the neoformation of cementum and collagen fibers on an implant in the presence of root residues occurs only in animal models or whether it may also occur in humans.