primary dentition, the set of 20 teeth that appears normally during infancy, consisting of four incisors, two canines, and four molars in each jaw. The teeth start developing at about the sixth week of fetal life as a thickening of the epithelium along the line of the future jaw. During the seventh week the epithelium splits longitudinally into labial and lingual strands. The former becomes the labiodental lamina, and the latter forms the dental lamina, which develops 10 enlargements in each jaw. The enlargements appear at about the ninth week and correspond to the future teeth. In most individuals, the first tooth erupts through the gum about 6 months after birth. Thereafter one or more teeth erupt about every month until all 20 have appeared. The primary teeth are usually shed between the ages of 6 and 13 years, although the timing varies greatly from person to person. Also called deciduous dentition, first dentition, primary teeth. Compare secondary dentition. See also predeciduous dentition, teething, tooth.
