Deciduous teeth important for the development of the child's speech, for the child's smile and play a role in chewing of food, although children who have had their primary teeth removed (usually as a result of Dental caries) can still eat and chew to a certain extent. In almost all European languages the primary teeth are called "baby teeth" or "milk teeth". In the United States and Canada, the term "baby teeth" is common. In some Asian countries they are referred to as "fall teeth" since they will eventually fall out. Various cultures have customs relating to the loss of deciduous teeth.
Dentition animals with two successions of teeth (deciduous, permanent) is referred to as "diphyodont", while the dentition of animals with only one set of teeth throughout life is "monophyodont". The dentition of animals in which the teeth are continuously discarded and replaced throughout life is termed "polyphyodont". The evolutionary origin of the vertebrate dentition remains contentious. Current theories suggest either an "outside-in" or "inside-out" evolutionary origin to teeth, with the dentition arising from odontodes on the skin surface moving into the mouth, or vice versa. Despite this debate, it is accepted that vertebrate teeth are homologous to the dermal denticles found