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Primary vs Permanent Dentition

Author: Shirley Chen

What are the similarities and differences between primary (baby) teeth and permanent (adult) teeth? Read on to find out!

In both primary and permanent dentition, there are three basic tooth forms: incisiform, caniniform, and molariform. Incisiforms include incisors, which have thin, blade-like edges that are used for cutting. Caniniforms are canines and have one pointed cusp for piercing and tearing. Molariforms include premolars and molars, each with multiple cusps primarily used for grinding. Premolars are only present in secondary dentition, and they replace the primary molars.1

The primary dentition consists of a total of twenty teeth, with 8 incisors, 4 canines, and 8 molars. The permanent dentition has thirty-two teeth, including 8 incisors, 4 canines, 8 premolars, and 12 molars. On average, the primary dentition is completely erupted by the age of three years. The first tooth of the permanent dentition erupts around the age of six years while primary teeth begin to exfoliate. The complete set of permanent teeth are present around the age of eighteen years.1

Primary teeth are smaller than their corresponding permanent successors, with the exception of the primary molars, which are larger than their permanent successors, the premolars. Enamel, the outer protective layer of every tooth, is thinner and softer in primary teeth when compared to permanent teeth.1 Consequently, primary teeth are more susceptible to decay than permanent teeth.2 With regards to the roots, permanent teeth have longer, more robust, and less divergent roots than primary teeth. Furthermore, pulp chambers in primary teeth take up more space relative to the crown than those of permanent teeth.1

As secondary teeth begin to erupt and primary teeth exfoliate, one might notice a difference in colour, specifically that the secondary teeth are more yellow than their predecessors. This difference is due to the fact that secondary teeth have more dentin, the layer beneath enamel, that is naturally more yellow in colour than enamel. Since enamel is naturally translucent, the colour of the dentin shows through.3

These are some basic similarities and differences between primary and permanent teeth. If you could choose one set of dentition, which one would be your primary choice?


[1] Ohshima, H. (2014). Dental and Oral Biology, Anatomy. Reference Module in Biomedical Sciences.

[2] What Every Parent Needs to Know About Baby Teeth. University of Illinois at Chicago (UIC) College of Dentistry. (2017, December 21).

[3] Why are my child's adult teeth coming in yellow? Growing Healthy Smiles Pediatric Dentistry. (2021, May 26).

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