Regional Veterinary Surgery

STRUCTURE OF TEETH

• The crown is the part of the tooth projecting above the gums and the root is the part contained within the bony tooth cavity or alveolus. The crown and root meet at the neck, which is covered by the gum.
• The hard portions of the tooth consist of the enamel, cementum and dentine. The dense, pearly white, outer layer of the crown is the enamel which is the hardest substance in the body. At the neck, enamel is continuous with the cementum which is a thin layer that covers the root except for the apical foramen. The cementum is bone like tissue and is difficult to distinguish from the dentine which it covers. The bulk of the tooth is formed by dentine which surrounds the pulp cavity. It is thickest in the crown and tapers to a point at the root. Its outer surface is covered by enamel in the region of crown and by the cementum in the region of the root.
• The soft portion of the tooth is the pulp which is composed of sensory nerves, arteries, veins and lymphatics and primitive connective tissues which hold them together. The small apical foramen at the end of the root enables the passage of vessels and nerves in and out of the tooth.
• The roots of the teeth are fairly constant. The incisor and canine teeth of both jaws have single root each. In the upper jaw, the first cheek tooth has one root, next two cheek teeth have two each and the last three cheek teeth have three roots each. In the lower jaw, the cheek teeth have two roots each, except the first and last which have one. The most important tooth clinically is the upper 4^th premolar (carnassial tooth) which has two anterior roots in a transverse plane and a single large posterior root.
• The outer surface of the incisor teeth is the labial surface and that of the cheek teeth, the buccal surface. The inner surface of the teeth is called as the lingual surface. The inner surface of the teeth which face the opposite dental arch is known as the occlusal or masticating surface.
• The teeth are held in sockets called alveoli. The periodontal membranes serve as periosteum to the alveolar bone and provide a firm attachment between the root of the tooth and the bone. It consists of thick collagen bundles and differs from the usual periosteum in that there are no elastic fibres.
• The gums (gingivae) cover the hard palate and the alveolar processes of the upper and lower jaws and surround the necks of the teeth. The gums are dense fibrous tissue and are covered with mucous membrane and are continuous with other soft tissues of the mouth.