MECHANISM OF ADHESION BETWEEN GINGIVAL JUNCTIONAL EPITHELIUM AND TOOTH ENAMEL

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1) In this study the detailed ultrastructure of the dental cuticle at the dentogingival border in monkeys was observed. The results suggest that the dental cuticle, is formed at the dentogingival border by an accumulation of basement membrane components and a dark amorphous material of uncertain biochemical nature at the enamel side of the lamina densa of the basement membrane of the junctional epithelium. While the dark amorphous material may be derived, as has been suggested, from serum proteins in gingival exudates or hemoglobin from degraded red blood cells, further studies are still needed to demonstrate the origin of this dark material.2) In nonmammalian species, characterization of the tooth basement membranes is still to be advanced. In this study, detailed ultrastructural observations of the basement membranes of the tooth of the shark were made in its various developmental stages. The results indicate that basement membranes of the developing shark tooth, as those in the mammalian tooth, play various roles, including anchoring, firm binding, and possible mediation of the transport of substances that are known to be vital for the development of the tooth.3) In order to elucidate the mechanism of adhesion between the gingiva and the tooth, detailed ultrastructural studies of the dentogingival border were done in the monkey. At the border, the internal basement membrane is firmly bounded to the junctional epithelium through hemidesmosomes. The lamina densa was closely associated at its enamel side with an additional layer (supplementary lamina densa), which had characteristics of the lamina densa. In nondemineralized tissues a part of the basement membrane, that is, the supplementary lamina densa was preferentially mineralized. The mineral deposit was continuous with that in the enamel, thus constituting an advancing edge of mineralization. Therefore, strong gingiva-tooth adhesion is established by partial mineralization of the internal basement membrane.