Wakasa Masanobu, Eshita Yoshiyuki, Nakanishi Kuniyuki, Isobe Tsutomu, Manago Kenji, Okamoto Masayuki, Isshiki Toshiyuki
Analytical Science Research, Kao Corporation, Wakayama, Wakayama Prefecture, 640-8580, Japan.
Personal Health Care Products Research, Kao Corporation, Sumida-ku, Tokyo, 131-8501, Japan.
Microsc Res Tech. 2017 May;80(5):511-524. doi: 10.1002/jemt.22825. Epub 2017 Jan 25.
The aim of this study was to clarify the fine structure of accumulated deposits on the surface of teeth that are considered to affect the gloss of teeth. The study was carried out using, as specimens, human incisor teeth having gloss, which were extracted from teenage donors and those incapable of showing gloss even by brushing which were extracted from donors in their 50s. Thin longitudinal sections of tooth enamel with accumulated deposits on the surface were prepared by focused ion beam (FIB) milling, and the fine structure was analyzed using a scanning transmission electron microscope (STEM) and a high resolution transmission electron microscope (HRTEM). By FIB, thin longitudinal sections could be prepared from tooth enamel together with organic and inorganic substances accumulated on the surface without artifacts. The accumulated deposits on the surface of teeth having gloss were composed of organic substances. However, it was first revealed by STEM observation that the accumulated solid deposits on the surface of teeth having no gloss had a complicated structure wherein inorganic and organic substances coexisted. It is suggested that the organic substances contain proteins derived from saliva. The inorganic substances were spherical and needle-like hydroxyapatites (HAs). It is considered that amino acids constituting the proteins affected the nucleus formation and the crystal formation of HA. It is considered that the unevenness of the accumulated deposits existing on the surface of tooth enamel having no gloss causes the decrease in gloss of teeth due to diffuse reflection of light.
本研究的目的是阐明牙齿表面累积沉积物的精细结构，这些沉积物被认为会影响牙齿的光泽。该研究以从青少年捐赠者处提取的有光泽的人类门牙以及从50多岁捐赠者处提取的即使刷牙也无光泽的牙齿作为标本进行。通过聚焦离子束（FIB）铣削制备了表面有累积沉积物的牙釉质纵向薄片，并使用扫描透射电子显微镜（STEM）和高分辨率透射电子显微镜（HRTEM）分析其精细结构。通过FIB，可以从牙釉质以及表面累积的有机和无机物质制备纵向薄片，且无伪影。有光泽牙齿表面的累积沉积物由有机物质组成。然而，通过STEM观察首次发现，无光泽牙齿表面的累积固体沉积物具有无机和有机物质共存的复杂结构。提示有机物质含有来自唾液的蛋白质。无机物质为球形和针状羟基磷灰石（HAs）。认为构成蛋白质的氨基酸影响了HA的成核和晶体形成。认为无光泽牙釉质表面存在的累积沉积物的不均匀性由于光的漫反射导致牙齿光泽度降低。
