Mammalian teeth have to sustain repetitive and high chewing loads without failure. Key to this capability is the periodontal ligament (PDL), a connective tissue containing a collagenous fibre network which connects the tooth roots to the alveolar bone socket and which allows the teeth to move when loaded. It has been suggested that rodent molars under load experience a screw-like downward motion but it remains unclear whether this movement also occurs in primates. Here we use synchroton micro-computed tomography paired with an axial loading setup to investigate the form-function relationship between tooth movement and the morphology of the PDL space in a non-human primate, the mouse lemur (Microcebus murinus). The loading behavior of both mandibular and maxillary molars showed a three-dimensional movement with translational and rotational components, which pushes the tooth into the alveolar socket. Moreover, we found a non-uniform PDL thickness distribution and a gradual increase in volumetric proportion of the periodontal vasculature from cervical to apical. Our results suggest that the PDL morphology may optimize the three-dimensional tooth movement to avoid high stresses under loading.

哺乳动物的牙齿必须承受重复和高咀嚼负荷而不会失败。这种能力的关键是牙周韧带 (PDL)，这是一种包含胶原纤维网络的结缔组织，将牙根连接到牙槽骨窝，并允许牙齿在加载时移动。有人提出，啮齿动物的臼齿在负载下会经历螺旋状的向下运动，但尚不清楚这种运动是否也发生在灵长类动物中。在这里，我们使用同步光子显微计算机断层扫描与轴向载荷设置配对来研究牙齿运动与非人类灵长类动物，小鼠狐猴（Microcebus murinus）。下颌和上颌磨牙的加载行为显示出具有平移和旋转分量的三维运动，将牙齿推入牙槽窝。此外，我们发现不均匀的 PDL 厚度分布和牙周血管从颈部到根尖的体积比例逐渐增加。我们的结果表明，PDL 形态可以优化三维牙齿运动，以避免负载下的高应力。