Topic 7.3 · Core · Paper 6
Human Teeth
Every tooth shape does one specific mechanical job, and every layer inside a tooth sits in a fixed order — enamel outside, dentine beneath it, pulp at the centre. Both of those facts are worth learning as exact, fixed relationships rather than a general impression of “teeth help you chew.”
The four tooth types and what each one does
| Tooth type | Shape | Function |
|---|---|---|
| Incisors | sharp, chisel-like cutting edge | cut and bite pieces off food |
| Canines | more pointed | grip and tear food |
| Premolars | broader surface | crush and grind |
| Molars | broadest chewing surface | crush and grind |
Each shape is suited to its action: a sharp edge concentrates force along a line to cut, a point concentrates force to grip and tear, and a broad flat surface crushes food between two faces. Together, the four types reduce food to smaller pieces, which is exactly the surface-area principle covered in physical digestion — teeth are one of the places that principle actually happens.
The most common error here is assigning the wrong action to the wrong shape: incisors do not grind, and molars do not cut. Canines specifically grip and tear rather than cut — cutting is the incisors’ job. Premolars and molars share the same function, so if a question asks for a function different from the molars, it is looking for the incisors or canines, not another broad-surfaced tooth.
Structure of a tooth
Cambridge requires a fixed set of named structures, in a fixed spatial order. Enamel is the hard, non-living outer covering of the crown — the outermost layer, and the one that takes the wear. Beneath it sits dentine, a softer layer that forms most of the bulk of the tooth. At the centre is the pulp, a living region containing nerves, which detect stimuli such as pain, and blood vessels, which supply the living tissue. Below the gum line, cement covers the root and helps anchor the tooth in place, and the whole tooth sits embedded in the bone of the jaw, surrounded by the gums.
Keep the order fixed in your head exactly as it is arranged in the tooth: enamel outside, dentine beneath it, pulp at the centre — never reversed. Enamel and cement are easy to mix up too, since both are protective outer layers, but they cover different regions: enamel covers the crown, cement covers the root.
Reading a tooth in an unfamiliar diagram
Because this unit also carries Paper 6, questions may ask you to identify these structures in a diagram or specimen image you have not seen before, rather than in one familiar, memorised drawing — so it is worth practising recognition of enamel, dentine, pulp, nerves, blood vessels and cement by their position and appearance, not only by a labelled picture from a textbook. Detailed root counts, exact cusp shapes, and the mechanisms of tooth decay all sit outside what this chapter requires — the structures above are the complete required list.
Teeth are only one part of physical digestion; the stomach’s own muscular contribution, and how the two compare, is covered in physical digestion.