Epithelial differentiation at the edentulous alveolar ridge in man. A stereological study.

The epithelial lining of the mucosa of the edentulous, maxillary alveolar ridge was subjected to an ultrastructural and stereological analysis. Four biopsies collected from the non-inflamed crest, i.e., the center over former tooth sockets, in non-denture-wearing female patients 30 to 55 years of age were processed for light and electron microscopy. At the light-microscopic level, epithelial thickness was determined histometrically. Electron micrographs were sampled at two levels of magnification, from five strata in regions of epithelial ridges and from three strata over connective tissue papillae. Standardized stereological point-counting techniques were employed to analyze a total of 990 electron micrographs. Observations and data revealed that at the alveolar ridge the oral epithelium is truly keratinizing and comprises four strata including a 40 +/- 5 micron-thick stratum corneum, which displays the oral keratin pattern. The histo- and cytodifferentiation were peculiar: (1) Compared to the neighbouring gingival and hard palate epithelium, that of the alveolar crest was markedly thicker, with elongated rete ridges indicating acanthosis. (2) The cytoarchitecture was identical neither to the gingival nor to the hard palate epithelium but revealed a mixture of features typical for either of these two epithelia. Reasons for this are explained on the basis of factors, possible genetic, inherent in epithelial cells that are possibly derived from both the gingival and the palatal environment.