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The primary dentition constitutes the first teeth to erupt in the pediatric patient. Comprised of 20 teeth, they are labeled based on an alphabetical system rather than the numbering system used for permanent teeth. The primary teeth are organized in two arches: the maxillary (upper) arch and the mandibular (lower) arch.[1] When divided on the mid-line sagittal plane, these teeth are organized into the right and left halves. Incisors and canines can be classified further as "anterior teeth" and molars and premolars as "posterior teeth." The primary teeth erupt during the first year and into the third years of life and are then exfoliated(shed) between the ages of 6 and 12. Since primary teeth are shed, as some trees shed their leaves, they are also referred to as deciduous teeth, which are eventually replaced by the adult permanent dentition.[2] Primary teeth are labeled in the following classification system and are designated in a clockwise direction: A: Right maxillary 2nd molar B: Right maxillary 1st molar C: Right maxillary canine D: Right maxillary lateral incisor E: Right maxillary central incisor F: Left maxillary central incisor G: Left maxillary lateral incisor H: Left maxillary canine I: Left maxillary 1st molar J: Left maxillary 2nd molar T: Right mandibular 2nd molar S: Right mandibular 1st molar R: Right mandibular canine Q: Right mandibular lateral incisor P: Right mandibular central incisor O: Left mandibular central incisor N: Left mandibular lateral incisor M: Left mandibular canine L: Left mandibular 1st molar K: Left mandibular 2nd molar Eruption(appearance) and exfoliation(shedding) of the primary dentition occur in the following order: The central incisors of the upper teeth (maxillary teeth) erupt at 8 to 12 months and exfoliate at 6 to 7 years. The lateral incisors of the upper teeth erupt at 9 to 13 months and exfoliate at 7 to 8 years. The canines of the upper teeth erupt at 16 to 22 months and exfoliate at 10 to 12 years. The first molar of the upper teeth erupts at 13 to 19 months and exfoliates at 9 to 11 years. The second molar of the upper teeth erupts at 25 to 33 months and exfoliates at 10 to 12 years. The central incisors of the lower teeth(mandibular teeth) erupt at 6 to 10 months and exfoliate at 6 to 7 years. The lateral incisors of the lower teeth erupt at 10 to 16 months and exfoliate at 7 to 8 years. The canines of the lower teeth erupt at 17 to 23 months and exfoliate at 10 to 12 years.

The second molar of the upper teeth erupts at 25 to 33 months and exfoliates at 10 to 12 years. The central incisors of the lower teeth(mandibular teeth) erupt at 6 to 10 months and exfoliate at 6 to 7 years. The lateral incisors of the lower teeth erupt at 10 to 16 months and exfoliate at 7 to 8 years. The canines of the lower teeth erupt at 17 to 23 months and exfoliate at 10 to 12 years. The first molar of the lower teeth erupts at 14 to 18 months and exfoliates at 9 to 11 years. The second molar of the lower teeth erupts at 23 to 31 months and exfoliates at 10 to 12 years. The primary dentition should not be confused with the permanent dentition, composed of 32 teeth with 16 teeth in each arch. Each of the primary molars is replaced by permanent, premolar teeth. There are three permanent molars in each quadrant that are not succeeded by primary teeth and may be referred to as non-succedaneous teeth. The arrival of these teeth, 12 in total, gives permanent dentition 32 teeth compared to the 20 teeth of primary dentition.