Abstract
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.
Original language | English (US) |
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Pages (from-to) | 41-51 |
Number of pages | 11 |
Journal | Connective tissue research |
Volume | 55 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2014 |
Funding
Support from NICDR grant DE001374 (to Prof. Arthur Veis) is gratefully acknowledged. The author thanks Dr. Xianghui Xiao for support during synchrotron microCT data acquisition at station 2-BM of APS. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Keywords
- Biomineralization
- Calcite
- Mechanical properties
ASJC Scopus subject areas
- Molecular Biology
- Biochemistry
- Rheumatology
- Cell Biology
- Orthopedics and Sports Medicine