Numerical frequency of epithelial abnormalities, particularly microkeratocysts, in the developing human oral mucosa.

Clinically manifest gingival and median palatal cysts in the adult are relatively rare lesions. The present study using Epon-embedded material and serial paraffin sections of fifty-five human heads, approximately 8 to 22 weeks of fetal age, demonstrated that (1) dental lamina-derived microkeratocysts develop and increase in number from the twelfth to the twenty-second week, with a maximum of 190 cysts per fetus; (2) midpalatal microkeratocysts reach a peak number of below 20 per fetus at week 14 and do not become more numerous with time. In addition, morphologic findings offer evidence of fetal cyst development through differentiation phenomena and reconfirm the discharge mechanism responsible for cyst disappearance. It appears that cyst development through epithelial differentiation is an essential step if it is to be at all possible for discharge to occur. Most microcysts of the alveolar crest and the midpalatal region are apparently discharged shortly after birth, therefore, the respective cysts in the adult are rare.