Incisor tooth. Coloured scanning electron micrograph (SEM) of a section through an incisor. Incisors are located near the front of the mouth and are used for cutting through tough foods, particularly meat. At the centre of the tooth (dark oval) is the pulp cavity, containing specialised connective tissue and sensory nerve fibres (dental pulp). The bulk of the tooth is dentine (purple at tip, green at root), a mineralised tissue similar to bone. Surrounding the dentine is enamel (thin white layer at top), the hardest substance in the body. The tooth is embedded in the periodontal membrane (dark green) and alveolar bone (yellow). At the surface of the gum is the gingiva (white), the soft tissue that covers the alveolar bone.