Published online by Cambridge University Press: 04 August 2010
Before processes of ingestion, mastication and swallowing can be considered, the structure of teeth and their general arrangement in the face have to be sketched. Function creeps in, but only so that the sense in certain structural arrangements is clarified.
WHAT ARE TEETH?
The teeth of a mammal are stones, anchored in tight-fitting holes in the bones of the upper and lower jaws and projecting through the lining tissue of the jaw into the mouth (Fig. 2.1). The part of the tooth that projects into the mouth is called the tooth crown while that part set into the jaw is called its root. The working surface of the crown is described by its most prominent features: pointed elevations are called cusps if they are large, tubercles if they are small. Roughly circular depressions are called fossae (singular, fossa). Raised folds can be called ridges or crests (sometimes written as cristae; singular, crista), but I will sometimes refer to these features later as blades. The creases that run between the bases of cusps are called fissures. Figure 2.2 shows some of these features diagrammatically on a typical mammalian molar and gives compass bearings needed to identify them unequivocally in a skull. Many features, such as fissures (one is indicated on Fig. 2.1), are depicted best in photographs and reflect the fact that the cusps of most molars rise like mountains alongside V-shaped valleys. Fissures are like the rivers running at the base of those valleys.