Van Nievelt A F, Smith K K
Department of Biological Anthropology and Anatomy, Duke University Medical Center, Durham, NC 27710, USA.
Arch Oral Biol. 1997 Aug;42(8):587-91. doi: 10.1016/s0003-9969(97)00048-4.
Rotation of a tooth around an axis perpendicular to the occlusal plane through angles approaching 180 degrees is a rare anomaly found in the mammalian dentition. A specimen of Monodelphis domestica was found to show such extreme rotation of both lower last molars, with consequent disruption of normal occlusion and wear. A review of the literature discovered 41 other reported cases of extreme rotation, from four different orders of mammals. The distribution of extreme rotation within the dentition can be summarized as follows. It is found only in isolated teeth or in contralateral pairs of teeth. Bilateral rotation is far more common than would be expected based on the chance of the independent occurrence of two rotations. Extreme rotation has a significantly higher frequency in upper rather than lower teeth, in premolars rather than other teeth, and on the left- rather than the right--hand side. The incidence of extreme rotation across mammals was estimated to be approx. 1 in 5850.
牙齿围绕垂直于咬合平面的轴旋转接近180度是在哺乳动物牙列中发现的一种罕见异常。发现一只家短尾鼩的标本显示两颗右下最后磨牙出现了这种极端旋转，从而导致正常咬合和磨损受到破坏。对文献的回顾发现了另外41例极端旋转的报告病例，来自四个不同目哺乳动物。牙列中极端旋转的分布情况可总结如下。它仅见于孤立牙齿或对侧牙齿对。双侧旋转远比基于两次旋转独立发生的概率所预期的更为常见。极端旋转在上颌牙齿而非下颌牙齿、前磨牙而非其他牙齿以及左侧而非右侧出现的频率显著更高。据估计，整个哺乳动物中极端旋转的发生率约为5850分之一。
