Now that we’ve looked at the muscles of the cheek and lips, we’ll move on to look at the teeth.
These are the lower teeth of a young adult. In the full dentition there are sixteen teeth above and sixteen below, thirty two in all. In each quadrant there are two incisors, one canine, two premolars, and three molars. (This individual’s third molars have been removed.)
The incisor teeth are flat and chisel shaped. The canine teeth have a crown that’s cone shaped, and a massive root which forms a prominence in the gum. The premolar teeth are broad, and short from front to back. They have two projecting cusps.
The molars are longer from front to back than the premolars, and have from three to five cusps.
Each tooth consists of a crown, which projects above the gingiva, and a root or roots which are embedded in bone. The tip of the root is called the apex. The crown and the root meet at this slight narrowing, the neck. The crown is covered on the outside with enamel, which is extremely hard. The inner part of the crown, and the root, are made of dentin.
The tooth is fixed to the surrounding bone by a layer of specialized periosteum, the periodontal membrane or ligament. The space within the tooth is the pulp cavity. The pulp of the tooth contains blood vessels and nerves, which enter through the apical canal.
The incisors and canines have one root, the premolars have a single root that’s forked at the end. The molar teeth have multiple roots: the upper ones have three, the lower ones usually have two.