Epithelial differentiation at the mucogingival junction: a stereological comparison of the epithelia of the vestibular gingiva and alveolar mucosa.

The epithelial lining of normal human vestibular gingiva and the adjoining alveolar mucosa was subjected to a comparative stereological analysis. Five biopsies collected from 11 to 12 year-old males and females were selected from a total of 14 specimens and, under standardized conditions, processed for light- and electron microscopy. At two levels of magnification, electron micrographs were sampled from five strata in the oral-gingival, and from four strata in the alveolar-mucosal epithelium, mostly in regions of epithelial ridges. Standardized sterological point counting techniques were employed to analyze a total of 710 and 540 electron micrographs from the oral-gingival and the alveolar-mucosal epithelium, respectively. The two epithelia, although of similar thickness, show different differentiation patterns. The oral-gingival epithelium consists of four cytologically different strata, the major differentiation step occurring between the lower and upper stratum spinosum of epithelial ridges. Standardized stereological point counting techniques were alveolar-mucosal epithelium, consisting of two cytologically different cell compartments, displays a broad, superficial zone of differentiated flat cells, with 60% of the cytoplasm filled with a dense network of cytoplamic filaments. The major differentiation step occurs between basal and lower spinous layers. Differentiation phenomena in both epithelia are discussed and individual variations are interpreted in view of genetically determined factors.