牙釉质纳米微晶龋溶解的高分辨电镜观察

目的 在晶格水平上探讨牙釉质磷灰石纳米微晶的龋溶解机制及其与釉质微晶中心暗线的关系。方法 应用高分辨透射电镜结合氩离子减薄制样技术，对初期釉质龋病变体部的晶体结构进行观察。结果 在初期釉质龋的病变体部，釉质纳米微晶主要以中心优先溶解的方式溶解，偶见晶体周边溶解现象。单个釉质微晶的初期溶解首先表现为沿微晶中心暗线的多个亮斑，其晶格条纹模糊、弯曲或断裂，邻近亮斑可相互融合形成大的亮区，进而形成微晶的中心穿孔。龋溶解微晶的中心穿孔与中心暗线的出现部位相符，并可见中心穿孔沿中心暗线延伸。结论 牙釉质纳米微晶的初期龋溶解与品格缺陷密切相关；微晶中心优先溶解现象可部分归因于晶体的中心暗线，中心暗线可能显示微晶对龋溶解较为敏感的区域。

High-resolution electron microscopy of carious dissolution of enamel nano-crystals

Objectives To investigate the carious dissolution mechanism of enamel apatite nano-crystals at lattice fringe level and the possible correlation between the carious dissolution and the appearance of central dark line (CDL) in enamel crystals. Methods The body of the lesion in incipient enamel caries was observed by high resolution transmission electron microscopy (HRTEM,JOEL-2010 operating at 200 kv), combined with selected-area argon-ion-beam thinning technique. Results In the body of the lesion, the preferential core dissolution was found in most of enamel nano-crystals, whereas the peripheral dissolution of individual crystal could be occasionally observed. The initial carious dissolution of individual enamel apatite crystal occurred as a number of small electron-lucent spots along the central dark line with blurry, bent or disconnected lattice fringes. These small electron-lucent spots fused with each other to form large electron-lucent areas. Finally the central perforation was frequently seen in the crystals. The CDL always appeared in the same place with central perforation in carious crystals, which could be seen to extend along the CDL. Conclusions The initial carious dissolution is directly related to the lattice defects in the enamel nano-crystals. The preferential core dissolution can be partly ascribed to the CDL, which is presumed to be particularly susceptible area to caries.