Prenatal development of the alveolar bone of human deciduous incisors and canines

The formation of the human alveolar process around the incisors and canines is a hitherto unreported aspect of fetal oral development. The question is how, where, and when the alveolar process is formed. The purpose of this s tudy was to elucidate the questions where and when and hence to analyze the pattern of formation of the alveolar bone around developing human deciduou s canine and incisor teeth. The study was conducted with material selected from a sample of 61 normal human fetuses, legally or spontaneously aborted. Fertilization ages ranged from 9 to 22 weeks, crown-rump Length from 25 to 205 mm, and foot length from 4 to 34 mm. From this material, 7 maxillae an d 10 mandibles were selected for the study according to developmental stage s of the canines and incisors and according to the orientation of the histo logical sections. The skeletal investigation consisted of macroscopic and m icroscopic analysis of the mandibles and maxillae. The investigations revea led the absence of bone between the central and lateral incisors in the man dibles and maxillae of fetuses below the ages of 21 and 22 weeks, respectiv ely. Ln three specimens, alveolar bone between the central and lateral inci sors was recorded (21, 21, and 22 weeks of fertilization). Absence of bone labial to the canine was recorded in all fetuses investigated. In all other regions, alveolar bone occurred as a regular finding. The present study ha s shown that alveolar bone formation is strictly coordinated with tooth for mation. Alveolar bone occurs later in the area labial to the canine and in the region between the central and lateral incisors than it does in other a reas associated with the incisor/canine regions. Knowledge of this pattern in the formation of the alveolar process seems to be of importance for a fu ture elucidation of how the alveolar process is initially formed.