The tooth located in the primary dentition of the mandible distal to the primary canine tooth. It is succeeded by the mandibular first premolar. It has a crown elongated and oval in a mesio-distal direction and has four cusps (mesio-buccal, disto-buccal, mesio-lingual, disto-lingual), the largest of which is the mesio-lingual. A mesio-distal groove (fissure) separates the buccal from the lingual cusps and terminates at the mesial and distal marginal ridges. The lingual half of the tooth is narrower than the buccal and the mesio-lingual angle of the crown is markedly obtuse. A transverse enamel ridge frequently connects the mesio-lingual and mesio-buccal cusps to create mesial and distal pits (fossae). The buccal surface of the crown is very bulbous towards the cervical margin where there may be a distinct tubercle in the mesio-cervical part. It has a mesial and a distal root which diverge markedly to make room for the tooth germ of the mandibular first premolar. The root apices may converge towards each other, further embracing the permanent tooth germ, which can result in its unintentional removal if extraction is attempted when the roots are fully formed. Calcification of the tooth begins at about 5 months of foetal life. The tooth erupts at about 12 months after birth and the calcification of the root is complete at about 2½ years.
Primary (deciduous) molars