The morphology and the dental formula (see Table: Dental Formulas of Various Animal Species Dental Formulas of Various Animal Species The morphology and the dental formula (see Table: Dental Formulas of Various Animal Species) of mammalian teeth are variable and closely related to the animal’s alimentation. Each tooth has... read more ) of mammalian teeth are variable and closely related to the animal’s alimentation.
Each tooth has a crown above the gum line and one to several roots below the gum line. Dental pulp, which contains nerves, blood and lymphatic vessels, connective tissue, and odontoblasts, occupies the central portion of the tooth (pulp cavity). The pulp cavity is surrounded by dentin, a hard but porous material. Enamel, a hard, mineralized formed by ameloblasts prior to tooth eruption, coats the coronal portion of the tooth. Cementum, bone-like mineralized connective tissue formed by cementoblasts, is over the root. Gingiva covers the root and the base of the crown. The major connective tissue attachment of the tooth, the periodontal ligament, anchors the roots to the alveolar bone and holds the tooth in its alveolus (socket).
Most mammals are diphyodont (ie, having two generations of teeth: an initial deciduous set of teeth succeeded by a permanent set of teeth). Elephants, kangaroos, and manatees are polyphyodont, having successive generations of teeth that are continually replaced throughout life.
Teeth can be specifically identified using anatomic nomenclature by their set (deciduous or permanent), side (left or right), arch (maxillary or mandibular), class (incisor, canine, premolar, and molar), and normal anatomic position in the mouth from mesial to distal (first, second, third, or fourth). A complete description allows specific identification of and communication about a particular tooth, as in deciduous left maxillary third premolar (notationally abbreviated dLMaxP3) or permanent right mandibular canine (notationally abbreviated RMandC). Variations do occur, with extra teeth designated as supernumerary, as in supernumerary right maxillary second premolar (notationally abbreviated sRMaxP2).
A common dental notation system popular in clinical practice is the modified Triadan system, which assigns a 3-digit number to a specific tooth. The hundreds place digit denotes the quadrant, and the subsequent digits identify the specific tooth number. In a clockwise direction (looking onto the animal), the right maxillary quadrant is labeled “100,” the left maxillary quadrant “200,” the left mandibular quadrant “300,” and the right mandibular quadrant “400.” When referring to the deciduous dentition, these respective quadrants are numbered 500–800. Each tooth is given a 2-digit number according to its position from midline, with the central incisor being 01, the canine tooth 04, and the first molar 09. For example, in horses, the left lower second premolar is tooth 306, and the last molar on the right mandible is tooth 411. Missing teeth are skipped in the numbering sequence. For example, in cats, the tooth distal to the maxillary canine is—phylogenetically, developmentally, and anatomically speaking—the second premolar (106 or 206), whereas the first premolar has been lost during evolutionary history (ie, there is no 105 or 205).