Deciduous teeth, otherwise known as milk teeth, baby teeth, temporary teeth, are the first set of teeth in the growth development of humans and many other 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.
Deciduous teeth start to form during the embryo phase of pregnancy. The development of deciduous teeth starts at the sixth week of development as the dental lamina. This process starts at the midline and then spreads back into the posterior region. By the time the embryo is eight weeks old, there are ten areas on the upper and lower arches that will eventually become the deciduous dentition. These teeth will continue to form until they erupt in the mouth. In the deciduous dentition there are a total of twenty teeth: five per quadrant and ten per arch. The eruption of these teeth begins at the age of six months and continues until twenty-five to thirty-three months of age. The first teeth seen in the mouth are the mandibular centrals and the last are the maxillary second molars.The deciduous dentition is made up of central incisors, lateral incisors, canines, first molars, and secondary molars; there is one in each quadrant, making a total of four of each tooth.
All of these are replaced with a permanent counterpart except for the first and second molars; they are replaced by premolars. The deciduous teeth will remain until the age of six. At that time, the permanent teeth start to appear in the mouth resulting in mixed dentition. The erupting permanent teeth causes root resorption, where the permanent teeth push down on the roots of the deciduous teeth causing the roots to be dissolved and become absorbed by the forming permanent teeth. The process of shedding deciduous teeth and the replacement by permanent teeth is called exfoliation. This may last from age six to age twelve. By age twelve there usually are only permanent teeth remaining.
Teething age of deciduous teeth (American Dental Assotiation):
Central incisors : 6-12 months
Lateral incisors : 9-16 months
Canine teeth : 16-23 months
First molars : 13-19 months
Second molars : 22-33 months