Dentition Meaning: Primary, Mixed and Permanent Dentition Explained

Dentition is the dentist's word for the whole set of teeth. It covers which teeth are present, what shape they are and how they are lined up in the upper and lower jaw. When a dentist writes about a child's "mixed dentition", they mean a mouth that holds both milk and permanent teeth at the same time.

Do not confuse it with denture, which is a removable replacement for missing teeth. Our guide to dentures meaning explains that one.

A child starts with primary dentition, which is complete at around 2 to 3 years with 20 teeth. From about 6 years, permanent teeth begin to arrive and the mouth enters mixed dentition, which lasts until roughly 12 or 13 years. Permanent dentition is the adult set of up to 32 teeth.

Exact ages vary a good deal between children, and a few months earlier or later is normal.

Deciduous teeth are the milk teeth, also called primary or baby teeth. Deciduous comes from a Latin word meaning to fall off, the same root as deciduous trees that shed their leaves. They are called that because every one of them is meant to fall out and be replaced.

There are 20: eight incisors, four canines and eight molars. Permanent premolars later take the place of the milk molars. Read more in our guides on primary teeth and types of teeth, and on the later teeth, premolar teeth and molar teeth.

Knowing which stage a child is in tells a dentist whether crowding is likely to sort itself out, whether a milk tooth is overdue to fall, and when to plan braces. Adults get the same value from the term: a dentist describes missing, crowded or worn teeth against the normal permanent dentition.

Milk teeth hold space for the permanent ones, so decay in them is worth treating. See our guide on cavities in milk teeth.