Soft tissue attachment to implanted surfaces

The soft tissue attachment to natural teeth is composed of a specialized type of epithelium termed junctional epithelium together with a fibrous connective tissue attachment. Such an attachment is desirable at dental and percutaneous implants, but a true junctional epithelium has not been characterized at these sites. This study was undertaken to examine factors affecting soft tissue attachment to implanted surfaces. The hypotheses were that a connective tissue attachment is necessary to produce a stable epithelial attachment and prevent epithelial downgrowth, which may lead to exfoliation, but that such an epithelium may not have a phenotype identical to that of junctional epithelium. The present study utilized a model system in which Millipore filters with various surface modifications were implanted into the backskin of pigs or rats, subsequently removed and the nature of the soft tissue attachment examined.; When the effect of surface porosity of the filters was examined, it was found (Chapter IV) that a pore size of at least 3.0 micrometers was necessary for connective tissue attachment which inhibited the epithelial downgrowth that would otherwise result in exfoliation of the implant. This effect was evident as early as 10 days after implantation (Chapter V). Ingrowth of connective tissue into the porous implant stabilized the epithelium but did not promote an epithelium with the morphological characteristics of junctional epithelium. Treatment of the implant surface with cell attachment factors (Chapter VI) had a negligible effect on soft tissue attachment, although a titanium coating enhanced tissue adhesion. A biphasic implant (Chapter VII) was developed to provide a smooth surface for epithelial attachment and a porous surface for connective tissue attachment. Despite the formation of a stable tissue attachment, the epithelium differed from a "junctional" epithelium in not forming a basal lamina or hemidesmosomes. To examine the inductive influence of connective tissue, periodontal ligament fibroblasts were cultured on filters, which were then implanted (Chapter VIII). The resulting epithelium generally resembled junctional epithelium in morphology but lacked specialized attachment. This research offers basic information on the conditions necessary to promote a stable soft tissue attachment at the surface of dental or percutaneous implants.