Mineralization of basement membrane mediates dentogingival adhesion in mammalian and nonmammalian vertebrates.

In order to elucidate the mechanism of adhesion between the gingiva and the tooth, detailed comparative ultrastructural studies of the dentogingival border were done in the monkey and shark. The tissues were prepared with or without demineralization for the ultrastructural observations. At the border, the internal basement membrane, which is firmly bound to the junctional epithelium through hemidesmosomes, was specialized differently in these species. In the monkey, the lamina densa was closely associated at its enamel side with an additional layer which had characteristics of the lamina densa and was referred to as the supplementary lamina densa. In the shark, the lamina densa showed a unique, hemidesmosome-related specialization in the form of the intermittent occurrence of bulges along its surface facing the epithelium. In nondemineralized tissues a part of the basement membrane, that is, the supplementary lamina densa (monkey) and the main lamina densa but not bulges (shark), was preferentially mineralized. The mineral deposit was continuous with that in the enamel and enameloid/dentine, thus constituting an advancing edge of mineralization. The network arrangement of the mineral crystals in the monkey basement membrane resembled the pattern of the cord network of the basement membrane, suggesting the presence of a delicate mutual basement membrane-mineral interaction. Thus, the organic phase and the mineral phase are allowed to make contact at this mineralized area of the basement membrane and firmly bind to one another. Therefore, strong gingiva-tooth adhesion is established by partial mineralization of the internal basement membrane, in a way similar to that found in the previously reported association of maturation stage ameloblasts with the enamel.

Detection of selenium in generalized and localized argyria: report of four cases with X-ray microanalysis.

Electron microscopic and X-ray microanalytic studies were performed on four cases of argyria; one generalized and three localized. Deposition of electron dense granules was predominantly found on elastic fibers and around basal laminas of secretory portions of eccrine glands, although the amount of deposition was much less in the case of generalized argyria. In all four cases, X-ray microanalysis revealed that the depositions consisted mainly of silver, selenium, and sulfur. The importance of selenium in the detoxification of heavy metals was discussed.

Ultrastructure of the peri-implant junctional epithelium on single-crystal sapphire endosseous dental implant loaded with functional stress.

To elucidate the ultrastructure of peri-implant junctional epithelium (IJE) on single-crystal sapphire dental implants connected to the adjacent teeth by a metal superstructure, the peri-implant gingivae of ten monkeys were examined using a transmission electron microscope (TEM) at 3, 6 and 12 months after implant insertion. At the time of examination, the ultrastructural features of the IJE were almost identical to those of junctional epithelium (JE) attached to natural teeth, i.e. developed Golgi complexes, rough-surfaced endoplasmic reticulum, numerous free ribosomes and mitochondria. The innermost cells of IJE were attached to the implant surface by means of basal lamina-like structures (500-1000 A in thickness) and hemidesmosomes, but lacked a dental cuticle as seen on teeth. Such epithelial attachment of the IJE was often indistinct or absent at the apical portion of the IJE which terminated at the level of alveolar crest. A continuous basal lamina-like structure was also present along basal cells at the interface between the IJE and gingival connective tissue except at its apical portion.

[Gingival hyperpigmentation caused by dental restorations: the mechanism of detoxification using selenium]. / Hyperpigmentations gingivales issues de reconstitutions dentaires: mécanisme de détoxication par le sélénium.

X-ray microanalysis and electron diffraction made on granular metallic deposits of the gingival lamina propria, inducing partial periodontal tattoos, demonstrated that these deposits consisted of crystalline particles combining silver, sulphur and selenium. The role of selenium precipitating of silver and other metals as well as its role in detoxication are discussed.