Andrews A H
Res Vet Sci. 1975 Nov;19(3):322-6.
Radiographs were taken of both the right and left sets of maxillary teeth in 23 Friesian cattle of known age. The stage of development of each permanent tooth was ascertained and the degree of root resorption in the deciduous premolars was noted. All stages in individuals were later than for those of the mandibular cheek teeth except in the case of the first permanent premolar. As with mandibular cheek tooth development stages of formation occurred within certain age limits.
对23头已知年龄的弗里斯兰奶牛的左右上颌牙齿进行了X光检查。确定了每颗恒牙的发育阶段，并记录了乳前磨牙的牙根吸收程度。除第一恒前磨牙外，个体的所有阶段均晚于下颌颊齿。与下颌颊齿发育一样，形成阶段发生在特定的年龄范围内。
