Understanding the pathways and mechanisms of human tooth decay is central to the development of both prophylaxes and treatments, but only limited information is presently available about the initiation of caries at the nanoscale. By combining atom probe tomography and high-resolution electron microscopy, we have found three distinct initial sites for human dental enamel dissolution: a) along the central dark line (CDL) within carbonated apatite nanocrystals, b) at organic-rich precipitates and c) along high-angle grain boundaries. 3D maps of the atoms within hydroxyapatite nanocrystallites in sound and naturally-decayed human dental enamel reveal a higher concentration of Mg and Na in the CDL. The CDL is therefore thought to provide a pathway for the exchange of ions during demineralization and remineralization. Mg and Na enrichment of the CDL also suggests that it is associated with the ribbon-like organic-rich precursor in amelogenesis. Organic-rich precipitates and high-angle grain boundaries were also shown to be more vulnerable to corrosion while low-angle grain boundaries remained intact. This is attributed to the lower crystallinity in these regions.

中文翻译：

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人类蛀牙的纳米级途径-中央平面缺陷，富含有机物的沉淀物和高角度晶界。

了解人类蛀牙的途径和机制对于预防和治疗的发展至关重要，但是目前只有有限的信息可用于纳米级龋齿的发生。通过将原子探针层析成像和高分辨率电子显微镜相结合，我们发现了人类牙釉质溶解的三个不同的初始位置：a）沿碳酸盐磷灰石纳米晶体内的中心暗线（CDL）； b）富含有机物的沉淀物； c）沿高角度晶界。健全和自然腐烂的人类牙釉质中羟基磷灰石纳米晶体中原子的3D图谱显示CDL中Mg和Na的浓度较高。因此，认为CDL为脱盐和再矿化过程中的离子交换提供了途径。CDL的Mg和Na富集还表明，它与成釉过程中的带状有机富集前体有关。还显示出富含有机物的沉淀物和高角度晶界更容易受到腐蚀，而低角度晶界保持完好。这归因于这些区域中较低的结晶度。