Initial Calcification of the Human Permanent First Molar

¹ Department of Operative Dentistry, School of Dentistry, University of Washington, Seattle, Washington

The primary first and second molars and the permanent first molars were extracted from 73 human fetuses ranging in age from approximately 19 weeks intrauterine to 6 months after birth. The tooth buds were stained with alizarin red S to show the presence of calcified areas. A study of initial calcification as related to age was made.

Initial calcification was noted in every permanent first molar before birth. It occurred as early as 279 mm. C.R. length—or approximately 28 weeks intrauterine—or as late as 328 mm. C.R. length—or approximately 32 weeks intrauterine. Calcification may be present on as many as four cusp tips on each permanent molar before birth.

The relative time, location, and degree of initial calcification of the permanent first molars and the primary molars are quite consistent and have been described.