Once the first permanent tooth erupts into the mouth, the teeth are in the mixed (or transitional) dentition.

During primary dentition, the tooth buds of permanent teeth develop below the primary teeth, close to the palate or tongue.

Primary dentition starts on the arrival of the mandibular central incisors, usually at eight months, and lasts until the first permanent molars appear in the mouth, usually at six years.

Mixed dentition starts when the first permanent molar appears in the mouth, usually at six years, and lasts until the last primary tooth is lost, usually at eleven or twelve years.

Historically, for example, chopsticks according to one Japanese anthropologist who wrote a dissertation about it at the University of Michigan resulted in long term changes in the dentition, in the teeth, of the Japanese public.

The permanent dentition begins when the last primary tooth is lost, usually at 11 to 12 years, and lasts for the rest of a person's life or until all of the teeth are lost (edentulism).