Deciduous teeth Deciduous teeth Deciduous teeth, commonly known as milk teeth, baby teeth and temporary teeth, are the first set of teeth in the growth development of humans and other diphyodont mammals. They develop during the embryonic stage of development and erupt—that is, they become visible in the mouth—during infancy. They are usually lost and replaced by permanent teeth, but in the absence of permanent replacements, they can remain functional for many years. Primary teeth start to form during the embryo phase of human life. The development of primary teeth starts at the sixth week of tooth development as the dental lamina.
Dentition for example, the formula 2.1.2.3 for upper teeth indicates 2 incisors, 1 canine, 2 premolars, and 3 molars on one side of the upper mouth. The deciduous dental formula is notated in lowercase lettering preceded by the letter d: for example: di:dc:dp. An animal's dentition for either deciduous or permanent teeth can thus be expressed as a dental formula, written in the form of a fraction, which can be written as , or I.C.P.M / I.C.P.M. For example, the following formulae show the deciduous and usual permanent dentition of all catarrhine primates, including humans: The greatest number of teeth in