Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University , Chicago, IL , USA.
Connect Tissue Res. 2014 Jan-Feb;55(1):41-51. doi: 10.3109/03008207.2013.867338.
Sea urchins possess a set of five teeth which are self-sharpening and which continuously replace material lost through abrasion. The continuous replacement dictates that each tooth consists of the range of developmental states from discrete plates in the plumula, the least mineralized and least mature portion, to plates and needle-prisms separated by cellular syncytia at the beginning of the tooth shaft to a highly dense structure at the incisal end. The microstructures and their development are reviewed prior to a discussion of current understanding of the biomineralization processes operating during tooth formation. For example, the mature portions of each tooth consist of single crystal calcite but the early stages of mineral formation (e.g. solid amorphous calcium carbonate, ions in solution) continue to be investigated. The second stage mineral that cements the disparate plates and prisms together has a much higher Mg content than the first stage prisms and needles and allows the tooth to be self-sharpening. Mechanically, the urchin tooth's calcite performs better than inorganic calcite, and aspects of tooth functionality that are reviewed include the materials properties themselves and the role of the orientations of the plates and prisms relative to the axes of the applied loads. Although the properties and microarchitecture of sea urchin teeth or other mineralized tissues are often described as optimized, this view is inaccurate because these superb solutions to the problem of constructing functional structures are intermediaries not endpoints of evolution.
海胆有五套牙齿，这些牙齿可以自我磨砺，并且会不断替换因磨损而损失的材料。这种持续的替换过程决定了每颗牙齿都包含了从原始胚胎中离散的小板、最不矿化和最不成熟的部分，到在牙轴开始时由细胞合体分隔的小板和针状棱柱，再到切端的高度密集结构的一系列发育状态。在讨论牙齿形成过程中生物矿化作用的现有认识之前，先回顾一下这些微观结构及其发育过程。例如，每颗牙齿的成熟部分都由单晶方解石组成，但矿化过程的早期阶段（例如，固态无定形碳酸钙、溶液中的离子）仍在继续研究中。将不同的小板和针状棱柱固定在一起的第二阶段矿物的镁含量比第一阶段的棱柱和针状结构高得多，这使得牙齿能够自我磨砺。从力学角度来看，海胆牙齿的方解石性能优于无机方解石，我们回顾了牙齿功能的各个方面，包括材料特性本身以及小板和针状结构相对于施加的负载轴的取向的作用。尽管海胆牙齿或其他矿化组织的特性和微观结构通常被描述为优化，但这种观点并不准确，因为这些构建功能性结构的卓越解决方案是中间状态，而不是进化的终点。
