Summary
There is a range of experimental evidence consistent with the existence of planar defects in the apatite crystals which constitute dental enamel. The evidence includes the appearance of crystals in the electron microscope both before and after attack by caries or caries-simulating etchants, the cross-sectional shape of the crystals and their long lath-like morphology. It is suggested here that the defects are twin planes in the apatite structure and it is further shown that such twin faults can form with only minor disturbance to the structure.
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Rachinger, W.A., Phakey, P.P., Palamara, J. et al. Planar faults in dental hydroxy-apatite. Calcif Tissue Int 34, 209–210 (1982). https://doi.org/10.1007/BF02411235
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DOI: https://doi.org/10.1007/BF02411235