Institute of Evolutionary Medicine, University of Zurich, 8057 Zurich, Switzerland.
Department of Evolutionary Anthropology, University of Vienna, 1090 Vienna, Austria.
Am J Phys Anthropol. 2019 Aug;169(4):646-663. doi: 10.1002/ajpa.23858. Epub 2019 May 17.
This study explores the outer and inner crown of lower third and fourth premolars (P , P ) by analyzing the morphological variation among diverse modern human groups.
We studied three-dimensional models of the outer enamel surface and the enamel-dentine junction (EDJ) from μCT datasets of 77 recent humans using both an assessment of seven nonmetric traits and a standard geometric morphometric (GM) analysis. For the latter, the dental crown was represented by four landmarks (dentine horns and fossae), 20 semilandmarks along the EDJ marginal ridge, and pseudolandmarks along the crown and cervical outlines.
Certain discrete traits showed significantly different regional frequencies and sexual dimorphism. The GM analyses of both P s and P s showed extensive overlap in shape variation of the various populations (classification accuracy 15-69%). The first principal components explained about 40% of shape variance with a correlation between 0.59 and 0.87 of the features of P s and P s. Shape covariation between P s and P s expressed concordance of high and narrow or low and broad crowns.
Due to marked intragroup and intergroup variation in GM analyses of lower premolars, discrete traits such as the number of lingual cusps and mesiolingual groove expression provide better geographic separation of modern human populations. The greater variability of the lingual region suggests a dominance of functional constraints over geographic provenience or sex. Additional information about functionally relevant aspects of the crown surface and odontogenetic data are needed to unravel the factors underlying dental morphology in modern humans.
本研究通过分析不同现代人群体之间的形态变异，探讨下颌第三和第四前磨牙（P₃、P₄）的外冠和内冠。
我们使用μCT 数据集，对 77 名现代人类的外釉质表面和牙本质-釉质交界（EDJ）的三维模型进行了研究，既评估了七个非度量特征，也进行了标准的几何形态测量（GM）分析。对于后者，用四个标志点（牙本质角和窝）、沿 EDJ 边缘脊的 20 个半标志点以及沿牙冠和牙颈部轮廓的虚拟标志点来表示牙冠。
某些离散特征显示出明显不同的区域频率和性别二态性。对 P₃和 P₄的 GM 分析均显示，不同人群的形状变化存在广泛的重叠（分类准确率为 15%-69%）。第一主成分解释了约 40%的形状变异，P₃和 P₄的特征相关性在 0.59 到 0.87 之间。P₃和 P₄之间的形状协变表达了高而窄或低而宽的牙冠的一致性。
由于下颌前磨牙 GM 分析中存在明显的组内和组间变异，离散特征，如舌侧尖的数量和近中舌侧沟的表达，能更好地对现代人类群体进行地理分离。舌侧区域的更大变异性表明，功能约束对地理起源或性别具有支配作用。需要更多关于牙冠表面的功能相关方面和牙发生数据的信息，以揭示现代人类牙齿形态背后的因素。
