Henry Gray (18251861). Anatomy of the Human Body. 1918.
The crown is directed vertically, and is chisel-shaped, being bevelled at the expense of its lingual surface, so as to present a sharp horizontal cutting edge, which, before being subjected to attrition, presents three small prominent points separated by two slight notches. It is convex, smooth, and highly polished on its labial surface; concave on its lingual surface, where, in the teeth of the upper arch, it is frequently marked by an inverted V-shaped eminence, situated near the gum. This is known as the basal ridge or cingulum. The neck is constricted. The root is long, single, conical, transversely flattened, thicker in front than behind, and slightly grooved on either side in the longitudinal direction.
FIG. 1001 Front view of the skull shown in Fig. 1000. Note the relation of the permanent incisors and cuspids to each other and the roots of the temporary teeth. (Noyes.) (See enlarged image)
The upper incisors are larger and stronger than the lower, and are directed obliquely downward and forward. The central ones are larger than the lateral, and their roots are more rounded.
The lower incisors are smaller than the upper: the central ones are smaller than the lateral, and are the smallest of all the incisors. They are placed vertically and are somewhat bevelled in front, where they have been worn down by contact with the overlapping edge of the upper teeth. The cingulum is absent.
The Canine Teeth (dentes canini) are four in number, two in the upper, and two in the lower arch, one being placed laterally to each lateral incisor. They are larger and stronger than the incisors, and their roots sink deeply into the bones, and cause well-marked prominences upon the surface.