Electron microscope observations on apatite crystallites in human dentine and enamel
The hardness of mineralised tissues has hindered close study of their fine structure until recent observations by Fernández-Morán and Engström (1)on thin sections of bone cut with a diamond knife disclosed the hydroxyapatite crystallites in the form of rod-shaped particles preferentially oriented in the direction of the collagen fibrils. The dimensions of these crystallites (about 200 Å × 30–60 Å) agree with evidence from X-ray studies, suggesting an association with one-third the collagen macro-period of about 640 Å.
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