Cusp Size Variability of the Maxillary Molariform Teeth

Abstract

The morphological differences of tooth crown components among the maxillary molariform teeth were investigated by means of an odontometric method. The second deciduous molar (dm2), and the first and second permanent molars (M1 and M2) were measured on 159 dental casts taken from Japanese males. Measurements taken on the tooth crown included the mesiodistal and buccolingual crown diameters, and the diameters of the four main cusps, the paracone, protocone, metacone and hypocone. In terms of overall crown sizes, dm2 was the smallest of the three teeth. The mesial cusps, the paracone and protocone, were significantly larger in the permanent molars (M1 and M2) than in the dm2 (P < 0.01). The distal cusps, the metacone and hypocone, were significantly larger in the M1 than in the dm2 and M2 (P < 0.01), and were similar in size in the dm2 and M2. The paracone was the most stable of the four main cusps in size. As for relative cusp size, the protocone increased distally from dm2 to M2, but no significant difference was found in the paracone. It is concluded that paracone size is proportionally stable regardless of overall tooth size.