25 Days of Skeletal Facts: Day 20 – The Teeth

As you are probably well aware, the function of your teeth is to mechanically break down food for digestion preparation. While your teeth are often included in the skeletal system, they are not actually made of bone. Dentine, a hard bonelike material, covers the pulp cavity, which is capped by enamel, a highly mineralized material (see image to the left). Like many other mammals, humans are diphyodont, meaning we develop two sets of teeth, our deciduous (baby) teeth and then our permanent (adult) dentition. Some animals, like bony fish and crocodiles, are polyphyodont with multiple sets of teeth, while others are monophyodont with only one set of teeth for life. Primates, including humans, have what is called ‘generalized dentition’, meaning we have different types of teeth so that our diet can be varied – the front teeth are used for cutting and the back teeth for grinding.

Permanent dentition of the maxilla (left) and mandible (right). Source: ResearchGate

Human dentition consists of 20 deciduous teeth that are replaced in adolescence and early adulthood by 32 permanent teeth. Each tooth sits in its own alveolar process within your mandible (see Day 18), the lower jaw, or your maxilla, the upper jaw. The dental formula for an adult human, referring to the number of incisors, canines, premolars, and molars respectively in one quadrant of the mouth, is 2 incisors, 1 canine, 2 premolars, and 3 molars (see above image). Since enamel is already 96% mineral, teeth survive very well in the fossil record, and usually hominins are represented by many dental elements. Tooth size and enamel thickness have been used to help determine the diet of our ancestors.

Paranthropus boisei (specimen OH 5). Source: Smithsonian

Due to its large cheek teeth and their extremely thick enamel, researchers hypothesize that Paranthropus boisei, a species that roamed Africa between 2.3 million year ago (mya) to 1mya, specialized in eating harder foods. This specimen specifically, seen on the right, was nicknamed the “Nutcracker Man“. Over evolutionary time our jaws have decreased in size, becoming more gracile. So much so that many people do not have room for their 3rd molars anymore. If you have had your wisdom teeth removed, you now have only 28 permanent teeth with 2 molars in each quadrant.

That’s all for your teeth, tomorrow we will explore the many sinuses of your skull.


Child and Adult Dentition. TeachMe Anatomy Series. 2020

Early development of the human dentition revisited. Hovorakova et al. Journal of Anatomy. 2018

The Human Bone Manual. White & Folkens. 2005

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