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 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.
Dental Formulas of Various Animal Species
Species | Deciduous Teeth | Permanent Teeth |
|---|---|---|
Horse | ||
Cowc Sheep Goat | ||
Pig | ||
Dog | ||
Cat | d | |
a Canine teeth usually appear only in male horses; the canine teeth are usually regressed or absent in mares. | ||
b Small premolars (wolf teeth) are often present, especially in the upper jaw but may be present in the mandible and may be unilateral or bilateral. | ||
c The canine tooth of domestic ruminants has commonly been counted as a fourth incisor. d The maxillary second premolar and maxillary and first molar can be absent in some cats. Dc = Deciduous canine. Di = Deciduous incisor. Dp = Deciduous premolar. C = Canine. I = Incisor. M = Molar. P = premolar. | ||
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).
Photograph of a dog skull with the left maxillary and mandibular permanent teeth numbered according to the modified Triadan system. Dogs have 42 permanent teeth (12 incisors, 4 canines, 16 premolars, and 10 molars). The incisors (101–103, 201–203, 301–303, 401–403) and canine teeth (104, 204, 304, 404) are single rooted. In the maxillary arch, the first premolars (105, 205) have 1 root, the second and third premolars (106, 107, 206, 207) have 2 roots, and the fourth premolars (108, 208) and first and second molars (109, 110, 209, 210) have 3 roots. In the mandibular arch, the first premolars (305, 405) have 1 root; the second, third, and fourth premolars (306–308, 406–408) and the first and second molars (309, 310, 409, 410) have 2 roots; and the third molars (311, 411) have 1 root.
Courtesy of Dr. Maria Soltero-Rivera
Schematic of the dentition of a horse (Equus caballus). Illustrated are the anatomical features of particular teeth, as well as the variations observed on the occlusal surfaces of the different types of teeth and as a function of age.
Illustration by Dr. Gheorghe Constantinescu.
Photographs of a donkey skull with the maxillary and mandibular permanent teeth numbered according to the modified Triadan system.
Courtesy of the Archaeozoological Reference Collection of the Institute of Topographic Anatomy, University of Veterinary Medicine, Vienna.
Schematic of the dentition of a small ruminant. Illustrated are the anatomic features of particular teeth, as well as the variations observed on the occlusal surfaces of the different types of teeth and as a function of age.
Illustration by Dr. Gheorghe Constantinescu.
Schematic of the dentition of a pig (Sus scrofa domesticus), including the anatomic features of particular teeth.
Illustration by Dr. Gheorghe Constantinescu.
Photograph of a dog skull with the left maxillary and mandibular permanent teeth numbered according to the modified Triadan system. Dogs have 42 permanent teeth (12 incisors, 4 canines, 16 premolars, and 10 molars). The incisors (101–103, 201–203, 301–303, 401–403) and canine teeth (104, 204, 304, 404) are single rooted. In the maxillary arch, the first premolars (105, 205) have 1 root, the second and third premolars (106, 107, 206, 207) have 2 roots, and the fourth premolars (108, 208) and first and second molars (109, 110, 209, 210) have 3 roots. In the mandibular arch, the first premolars (305, 405) have 1 root; the second, third, and fourth premolars (306–308, 406–408) and the first and second molars (309, 310, 409, 410) have 2 roots; and the third molars (311, 411) have 1 root.
Courtesy of Dr. Maria Soltero-Rivera
Schematic of the dentition of a horse (Equus caballus). Illustrated are the anatomical features of particular teeth, as well as the variations observed on the occlusal surfaces of the different types of teeth and as a function of age.
Illustration by Dr. Gheorghe Constantinescu.
Photographs of a donkey skull with the maxillary and mandibular permanent teeth numbered according to the modified Triadan system.
Courtesy of the Archaeozoological Reference Collection of the Institute of Topographic Anatomy, University of Veterinary Medicine, Vienna.
Schematic of the dentition of a small ruminant. Illustrated are the anatomic features of particular teeth, as well as the variations observed on the occlusal surfaces of the different types of teeth and as a function of age.
Illustration by Dr. Gheorghe Constantinescu.
Schematic of the dentition of a pig (Sus scrofa domesticus), including the anatomic features of particular teeth.
Illustration by Dr. Gheorghe Constantinescu.
For More Information
Verstraete FJM, Terpak CH. Anatomical Variations in the Dentition of the Domestic Cat. J Vet Dent. 1997; 14(4):137-140.
