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.