Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, Prague, 2, Czech Republic.
Institute of Geology of the CAS, v.v.i., Rozvojová 269, Prague, 6, Czech Republic.
Sci Rep. 2018 Apr 3;8(1):5544. doi: 10.1038/s41598-018-23826-0.
The monophyodont molar teeth, prismatic enamel and the complexity of enamel microarchitecture are regarded as essential dental apomorphies of mammals. As prominent background factors of feeding efficiency and individual longevity these characters are crucial components of mammalian adaptive dynamics. Little is known, however, to which degree these adaptations are influenced by the crystallographic properties of elementary hydroxyapatite crystallites, the only inorganic component of enamel. In a miniature pig where individual molars differ significantly in duration of their development and in enamel resistance to attrition stress, we found highly significant differences between the molars in the size of crystallites, amount of microstrain, crystallinity and in enamel stiffness and elasticity, all clearly scaled with the duration of tooth calcification. The same pattern was found also in red deer bearing different molar type. The results suggest that the prolongation of tooth development is associated with an increase of crystallinity, i.e. the atomic order of enamel hydroxyapatite, an obvious component of micromechanical property of mature enamel. This relation could contribute to prolongation of dental development, characteristic of mammals in general. The aspects of enamel crystallinity, omitted in previous studies on mammalian and vertebrate dental evolution, are to be taken in account in these topics.
单锥体臼齿、棱柱形釉质和釉质微观结构的复杂性被认为是哺乳动物的主要牙齿特征。作为影响进食效率和个体寿命的重要背景因素，这些特征是哺乳动物适应动态的关键组成部分。然而，人们对这些适应性在多大程度上受到釉质中唯一无机成分——基本羟磷灰石微晶的结晶特性影响知之甚少。在微型猪中，个体牙齿的发育时间和对磨损压力的釉质抵抗力存在显著差异，我们发现，在微晶的大小、微应变的数量、结晶度以及釉质的硬度和弹性方面，牙齿之间存在着高度显著的差异，所有这些都与牙齿钙化的持续时间明显相关。在具有不同臼齿类型的赤鹿中也发现了同样的模式。结果表明，牙齿发育的延长与结晶度的增加有关，即釉质羟磷灰石的原子有序性，这是成熟釉质的微观力学性能的一个明显组成部分。这种关系可能有助于延长一般哺乳动物的牙齿发育。在以前关于哺乳动物和脊椎动物牙齿进化的研究中忽略了釉质结晶度的问题，在这些研究中应该考虑到这一点。
