Regions of the Head 8. Oral Cavity & Pharynx Table 8.2 Morphology of the maxillary permanent teeth Tooth Crown Surfaces Root(s) Root canal(s) Central incisors (8, 9) Lateral incisors (7, 10) Canines (6, 11) 1st premolar (5, 12) 2nd premolar (4, 13) 1st molar (3, 14) 2nd molar (2, 15) Roughly trapezoidal in the labial view; contains an incisal edge with 3 tubercles (mamelons) Labial: convex Palatal: concavoconvex 1 rounded root Usually 1 Roughly trapezoidal with 1 labial cusp Labial: convex Palatal: concavoconvex 1 root; the longest of the teeth Usually 1 2 cusps (1 buccal, 1 palatal), separated by a central fissure 4 cusps (1 at each corner of its occlusal surface); a ridge connects the mesiopalatal and distobuccal cusps 4 cusps (though the distopalatal is often small or absent Buccal, distal, palatal, and mesial: all convex, slightly flattened. The mesial surface often bears a small pit that is difficult to clean and vulnerable to caries Occlusal: more oval than the mandibular premolars Buccal, distal, palatal, and mesial: all convex, slightly flattened Occlusal: rhomboid 2 roots (1 buccal, 1 palatal) 1 root divided by a longitudinal groove and containing 2 root canals Usually 2, one per root 1 or 2 3 roots (2 buccal, 1 palatal) 3 or 4 (mesial root may have 2 canals) 3 roots (2 buccal, 1 palatal), occasionally fused 3 roots (2 buccal, 1 palatal), often fused 3 or 4 (mesial root may have 2 canals) Complex canal system 3rd molar (1, 16) 3 cusps (no distopalatal) The maxillary teeth are supplied by the posterior superior alveolar a. (molars), middle superior alveolar a. (premolars), and the anterior superior alveolar a. (incisors and canines); venous drainage is via the alveolar vv. that drain to the pterygoid plexus. Innervation is via the posterior, middle, and anterior superior alveolar nn. (same distribution as the arteries). Lymph from the maxillary teeth drain to the submandibular nodes. Buccal Marginal ridge Transverse fissure A Palatal Mesial fossa Mesiobuccal cusp Central fossa Distobuccal cusp Cusp tip Fossae Marginal ridge Longitudinal fissure Cusp tip Mesiopalatine cusp Cusp of Carabelli Distopalatal cusp B Distal fossa Fig. 8.17 Maxillary first premolar and first molar Occlusal view. Fig. 8.18 Cusp-and-fissure occlusion With the mouth closed (occlusal position), the maxillary teeth are op- posed to their mandibular counterparts. They are offset relative to one another such that the cusps of one tooth fit into the fissures of the two opposing teeth (cusp-and-fissure occulsion). Because of this arrange- ment, every tooth comes into contact with two opposing teeth. This offset results from the slightly greater width of the maxillary incisors. A class I occlusion is a “normal” occlusion where the lower anterior teeth occlude with the cingulum of the upper anterior teeth. A class II occlu- sion is when the lower teeth occlude behind the cingulum of the upper anterior teeth. A class III occlusion is when the lower anterior teeth oc- clude in front of the cingulum of the upper anterior teeth. Crossbites are when the teeth are not in the usual buccal-lingual relationship. 209