The etiology of osseous deformities of the head, face, jaws and teeth . oot, the greater the degree of rotation mustbe before the lateral finds a resting-place. If the diameterwere equal to the space left, and there were no impinging onthe root, there would be no displacements. But when thespace is not sufficient for the lateral and a pressure is broughtto bear on one side of either cutting-edge or root, there mustbe a partial rotation, which is proportioned to the diameter ofthe cutting-edge. The wedge-shaped character of the crownassists in rotation, as the rounded angle of the anterior cusp

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The etiology of osseous deformities of the head, face, jaws and teeth . oot, the greater the degree of rotation mustbe before the lateral finds a resting-place. If the diameterwere equal to the space left, and there were no impinging onthe root, there would be no displacements. But when thespace is not sufficient for the lateral and a pressure is broughtto bear on one side of either cutting-edge or root, there mustbe a partial rotation, which is proportioned to the diameter ofthe cutting-edge. The wedge-shaped character of the crownassists in rotation, as the rounded angle of the anterior cusp THE HEAD, FACE, JAWS AND TEETH 439 offers less resistance than a line or surface. This gives riseto the commonest form of irregularity (Nos. 1 and 2; Figs. 188and 184), in which the mesial surface of the lateral overlapsthe distal surface of the central, while the distal surface ofthe lateral is either in a line with the cuspid or just backof it. 3. In those cases where the lateral is in a line with thecuspid (Fig. 185), but its mesial surface is behind the central.. Fijr. 183.