The interface of the crevicular gingiva with the surface of a dental implant is a critical zone representing the potential biological seal which protects the underlying bone and soft tissue-supporting mechanisms from destructive extraneous substances. Ultrastructural examination of regenerated junctional epithelial cells interfacing surgically placed endosteal dental implants, comprised of alpha-alumina oxide ceramic in single crystalline form, exhibited an external basal lamina and linear body located between the external surface epithelial cell and the implant. In addition, hemidesmosomes were located at intervals along the outer junctional epithelial plasma membrane. The component substructures of the basal lamina and the hemidesmosomes were similar to those seen interfacing natural teeth. The linear body was an electron-dense structure between the lamina densa and the inert biomaterial. This study provides ultrastructural evidence for the presence of an attachment complex between gingiva and aluminum oxide implants which is analogous to that seen around natural teeth. These data support concept that a viable biological seal can develop around endosteal dental implants and provide support for satisfactory clinical service.

The ultrastructural and histological characteristics of the filiform papillae of the cow tongue are described. These large, conical papillae display a fully keratinized external projection, which demonstrates a dominant hard keratin core partially ensheathed by soft keratin. This biostructure differentiates from a dominant posterior cell line, leading to the hard keratin core, and a thinner anterior cell line which, with contributions from an inter-papillary cell line, appears responsible for an attenuating sheath of soft keratin around the hard keratin core. The hard keratin cell line differentiates from cells devoid of keratohyalin granules (KHG), which are rich in thick bundles of tonofilaments. The soft keratin cell line differentiates from cells containing both eosinophil and basophil KHG and dispersed tonofilaments. The bovine filiform papilla also appears similiar in biostructure to the mammalian hair shaft and the ‘filiform hairs’ of the rat penis.

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The fabrication, characterization, and clinical results of porous rooted alumina dental implants in animals are presented. Failures of all implants occurred in less than six months and were attributed to the presence of microporosity on the crown and cervical portion of the implant which prevented the establishment of an effective biological seal between the oral cavity and the alveolus.

The purpose of this report is to describe ultrastructural observations of the bone and associated tissues supporting 24 unloaded endosteal dental implants placed in mongrel dogs (canis familiaris). The following 3 specific areas of the supporting tissues were targeted: 1) the osteocyte populations; 2) the mineralized collagen fiber matrix of the bone; and 3) an electron dense interfacial deposit. To investigate these areas, transmission electron microscopy and high voltage electron microscopic (HVEM) protocols were emphasized. HVEM permitted stereologic observations. Further, all observations were obtained from undecalcified tissues obtained from animals with commercially available implants placed into the mandible. From the study we observed a mineralization pattern of the implant supporting bone that was similar to those events occurring naturally within the mandibular bone. Osteocyte morphology was similar whether the osteocytes were found well below the implant interface or close to the interface. Osteocytes within lacunae were routinely found close to the implant interface, often extending cellular processes through canaliculi to the bone-implant interface. At the interface, an electron dense deposit approximately 50 nm in thickness was often observed. In interfacial regions, densely mineralized collagen fibers were observed running primarily parallel to the implant surface. This dense mineralized tissue was separated from the interface by a mineralized, but finely fibrillar matrix of approximately 200 nm in thickness.