SEM part 1.

Radiation-induced caries is a common side effect of radiotherapy for head and neck cancer caused by pulpal hypovascularization and dentin collagen degradation by the direct action of ionizing radiation. A thorough understanding of radiation-induced changes in dental structure can lead to more effective and durable restorative treatments. The objective of this study was to analyze the microstructure and chemical composition of radiation-induced carious dentin (CD) compared with irradiated (ID) and sound dentin (SD) by using analytical techniques, including scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Specimens of CD and ID were obtained from patients who had undergone radiotherapy. SD that had not been irradiated was used as a control group. The specimens were sectioned, fixated, and dehydrated according to each type of analysis and equipment. The SEM analysis revealed varying degrees of microstructural degradation in both CD and ID groups. The EDS analysis showed higher levels of carbon in both ID and CD (p放射性龋（radiation-induced caries）是头颈部癌放疗常见的不良反应，其致病机制为牙髓血管减少（pulpal hypovascularization）以及电离辐射直接作用引发的牙本质胶原降解。充分掌握牙本质的辐射诱导变化，可助力开发更高效且持久的修复治疗方案。本研究旨在借助扫描电子显微镜（SEM）、能量色散X射线光谱（EDS）、X射线衍射（XRD）及傅里叶变换红外光谱（FTIR）等分析技术，对比分析放射性龋坏牙本质（radiation-induced carious dentin, CD）、照射后牙本质（irradiated dentin, ID）与健康牙本质（sound dentin, SD）的微观结构与化学成分。研究标本取自接受过放疗的患者，分别获取CD与ID样本，以未接受辐射的健康牙本质（SD）作为对照组。根据各类分析方法与设备的要求，对标本进行切片、固定及脱水处理。扫描电子显微镜分析结果显示，CD组与ID组均存在不同程度的微观结构降解。能量色散X射线光谱分析显示，ID组与CD组的碳元素水平均更高（p