A longitudinal radiographic study of the mineralization of 2nd premolars.

Odontogenesis of the 2nd premolar begins in the majority of cases at the age of 3-3 1/2 years, although this period can vary more widely than that for other permanent teeth. For this reason, aplasia of this group of teeth cannot be diagnosed as early and with the same degree of certainty. A group of 104 children aged 3-7 years in whom one or more tooth germs mesial to the 1st permanent molar were not visible in the various age groups was reexamined radiographically in the region where they apparently lacked the development of tooth germs. The second examination took place 16-24 months after the first, and a comparison was made of the two examinations. The study confirms that the 2nd premolar can be very late in developing and that the chance of this being so is greater in the maxilla than in the mandible.