ABC of oral health. Oral health and disease.

Teeth form mainly from neuroectoderm and comprise a crown of insensitive enamel surrounding sensitive dentine and a root that has no enamel covering. Teeth contain a vital pulp (nerve) and are supported by the periodontal ligament, through which roots are attached into sockets in the alveolar bone of the jaws (maxilla and mandible). The fibres of the periodontal ligament attach through cementum to the dentine surface. The alveolus is covered by the gingivae, or gums, which, when healthy, are pink, stippled, and tightly bound down and form a close fitting cuff with a small sulcus (gingival crevice) round the neck (cervical margin) of each tooth. The primary (deciduous or milk) dentition comprises four incisors, two canines, and four molars in each jaw (total of 20 teeth). The normal permanent (adult) dentition comprises four incisors, two canines, four premolars, and six molars in each jaw (32 teeth). Tooth development begins in the fetus, at about 28 days in utero. Indeed, all the primary and some of the permanent dentition start to develop in the fetus. Mineralisation of the primary dentition begins at about 14 weeks in utero, and all primary teeth are mineralising by birth. The permanent incisors and first molars begin to mineralise at or close to the time of birth, while the other permanent teeth start to mineralise later. Tooth eruption occurs after formation and mineralisation of the crown are largely complete but before the roots are fully formed. Neonatal teeth are uncommon and may be loose. They may damage the mother’s nipple during suckling, in which case they might need to be removed.