The sequence of eruption is an important aide memoire; the first permanent molars erupt first at 6 years of age. The other teeth appear at approximately yearly intervals corresponding to their sequence of eruption. If the sequence and dates of eruption are remembered, the timing of other events may be calculated by simple addition or subtraction. Birth to Two Years The permanent incisors and canines first develop lingual to the deciduous tooth germs at the level of their occlusal surfaces and in the same bony crypt. As their deciduous predecessors erupt, they move to a more apical position and occupy their own bony crypts. First teeth to erupt are the mandibular central incisors. The usual eruption sequence in the primary dentition is as follows. First the central incisors, followed in order by the lateral incisors, first molars, canines and second molars. Mandibular teeth usually precede the maxillary teeth. This sequence is not always followed. Time of eruption is usually stated as 6 months of age for the maxillary primary centrals, 7-8 months for the mandibular primary laterals and 8 or 9 months for the maxillary primary laterals. At about 1 year, the first primary molars erupt. At around 16 months, the primary cuspids appear. Two years is usually given as the age for the second primary molars to appear. Two Years to Six Years By two and a half years of age, the deciduous dentition is usually complete and in full function. By three years of age, the roots of all deciduous teeth are complete. First permanent molar crowns are fully developed and the roots are starting to form. The crypts of the developing permanent second
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