Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, 303 E. Chicago Ave, Chicago, IL 60611-3008, USA.
Department of Cell and Molecular Biology, Northwestern University, 303 E. Chicago Ave, Chicago, IL 60611-3008, USA.
Acta Biomater. 2014 Sep;10(9):3969-77. doi: 10.1016/j.actbio.2014.05.027. Epub 2014 Jun 6.
Dentin contains 1-2μm diameter tubules extending from the pulp cavity to near the junction with enamel. Peritubular dentin (PTD) borders the tubule lumens and is surrounded by intertubular dentin (ITD). Differences in PTD and ITD composition and microstructure remain poorly understood. Here, a (∼200nm)(2), 10.1keV synchrotron X-ray beam maps X-ray fluorescence and X-ray diffraction simultaneously around tubules in 15-30μm thick bovine and equine specimens. Increased Ca fluorescence surrounding tubule lumens confirms that PTD is present, and the relative intensities in PTD and ITD correspond to carbonated apatite (cAp) volume fraction of ∼0.8 in PTD vs. 0.65 assumed for ITD. In the PTD near the lumen edges, Zn intensity is strongly peaked, corresponding to a Zn content of ∼0.9mgg(-1) for an assumed concentration of ∼0.4mgg(-1) for ITD. In the equine specimen, the Zn K-edge position indicates that Zn(2+) is present, similar to bovine dentin (Deymier-Black et al., 2013), and the above edge structure is consistent with spectra from macromolecules related to biomineralization. Transmission X-ray diffraction shows only cAp, and the 00.2 diffraction peak (Miller-Bravais indices) width is constant from ITD to the lumen edge. The cAp 00.2 average preferred orientation is axisymmetric (about the tubule axis) in both bovine and equine dentin, and the axisymmetric preferred orientation continues from ITD through the PTD to the tubule lumen. These data indicate that cAp structure does not vary from PTD to ITD.
牙本质包含从牙髓腔延伸到接近釉质交界处的 1-2μm 直径的小管。管周牙本质（PTD）毗邻管腔，被管间牙本质（ITD）包围。PTD 和 ITD 的组成和微观结构差异仍知之甚少。在这里，使用（∼200nm）(2)、10.1keV 的同步加速器 X 射线束在 15-30μm 厚的牛和马标本中围绕小管同时映射 X 射线荧光和 X 射线衍射。围绕管腔的 Ca 荧光增加证实了 PTD 的存在，并且 PTD 和 ITD 的相对强度对应于 PTD 中假定的碳酸磷灰石（cAp）体积分数约为 0.8，而 ITD 为 0.65。在靠近管腔边缘的 PTD 中，Zn 强度强烈峰值，对应于假定的浓度为 0.4mgg(-1)的 Zn 含量约为 0.9mgg(-1)。在马标本中，Zn K 边位置表明存在 Zn(2+)，类似于牛牙本质（Deymier-Black 等人，2013），并且上述边缘结构与与生物矿化相关的大分子的光谱一致。透射 X 射线衍射仅显示 cAp，并且 00.2 衍射峰（米勒-布拉维指数）宽度从 ITD 到管腔边缘保持不变。cAp 00.2 平均优先取向在牛和马牙本质中都是轴对称的（关于小管轴），并且轴对称优先取向从 ITD 通过 PTD 延续到管腔。这些数据表明，cAp 结构从 PTD 到 ITD 没有变化。
