Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
J Anat. 2011 Jan;218(1):87-95. doi: 10.1111/j.1469-7580.2010.01234.x.
Teeth adopt a variety of different morphologies, each of which is presumably optimized for performing specific functions during feeding. It is generally agreed that the enamel cap is a crucial element in controlling the mechanical behavior of mammalian teeth under load. Incisors are particularly interesting in terms of structure-function relations, as their role in feeding is that of the 'first bite'. However, little is known how incisor cap morphology is related to tooth deformation. In the present paper we examine the mechanical behavior of mandibular central incisors in the cercopithecine primate Macaca mulatta under loads similar to those encountered during ingestion. We map three-dimensional displacements on the labial surface of the crown as it is compressed, using electronic speckle pattern interferometry (ESPI), an optical metrology method. In addition, micro-computed tomography is used to obtain data regarding the morphology of the enamel cap, which in the M. mulatta lower incisors exhibits missing or very little enamel on the lingual face. The results showed that although compressed along a longitudinal axis, deformation in the incisors mostly occurred in the lingual direction and orthogonal to the direction of the applied load. Both isolated, embedded teeth and teeth in the mandible showed considerable lingual deformation. Incisor deformation in the mandible was generally greater, reflecting the additional freedom of movement enabled by the supporting structures. We show that the association with adjacent teeth in the arch is significant for the behavior of the tooth under load. Finally, loading two teeth simultaneously in the mandible showed that they work as one functional unit. We suggest that these results demonstrate the importance of enamel cap morphology in directing deformation behavior; an ability stemming from the stiffness of the enamel cap overlying the more pliable dentin.
牙齿呈现出多种不同的形态，每种形态都可能是为了在进食过程中执行特定功能而优化的。人们普遍认为，牙釉质帽是控制哺乳动物牙齿在受力下机械行为的关键元素。在结构-功能关系方面，切牙尤其有趣，因为它们在进食中的作用是“第一口”。然而，对于切牙帽形态与牙齿变形之间的关系，人们知之甚少。在本文中，我们研究了在类似于进食过程中遇到的载荷下，食虫猴科灵长类猕猴下颌中切牙的机械行为。我们使用电子散斑干涉测量法（ESPI）在牙冠的唇面测量三维位移，这是一种光学计量方法。此外，还使用微计算机断层扫描（micro-CT）获取牙釉质帽形态的数据，猕猴的下切牙在舌侧没有或只有很少的牙釉质。结果表明，尽管沿着纵轴压缩，切牙的变形主要发生在舌侧方向，与施加的载荷方向正交。无论是孤立的、嵌入的牙齿还是下颌中的牙齿，都表现出相当大的舌侧变形。下颌中的切牙变形通常更大，这反映了支撑结构提供的额外自由度。我们表明，与弓上相邻牙齿的关联对牙齿在载荷下的行为很重要。最后，同时在下颌中加载两颗牙齿表明它们作为一个功能单元工作。我们认为，这些结果表明牙釉质帽形态在引导变形行为方面的重要性；这种能力源于覆盖在更柔韧的牙本质上的牙釉质帽的刚度。
