龋病是发病率最高的口腔疾病，也是全世界最流行的疾病之一。太赫兹光谱成像技术因具有宽频带光谱分析能力强、空间分辨率高、电离辐射低等优势，有望成为龋病诊断的新技术手段。本文以含牙本质龋的牙齿切片为研究对象，进行反射式太赫兹光谱扫描，以频域幅值为参数对样品的光谱数据做二维重构成像，获得多幅不同频率下的龋齿太赫兹光谱图像。为了解决单一参数所得的龋齿太赫兹图像动态范围小、对比度低，边缘和细节位置模糊不清的问题，采用小波梯度域重建的融合方法，将多幅图像中梯度幅值较大的部分集中于一幅图像上，得到了一幅细节特征更加清晰完整的新图像。实验结果表明，融合后的图像相较于融合前的图像在信息熵、平均梯度以及对比度上均有所提高，不同组织之间的区分效果更加显著。

为实现早期龋齿的无损检测，研究了一种基于自体荧光效应的龋齿检测方法。从光谱学角度对不同龋齿的特征光谱进行实验研究，利用荧光光谱仪采集各样品的激发、荧光光谱，采用Savitzky-Golay平滑法对光谱进行预处理。健康牙齿与龋齿的激发峰值波长位于405 nm附近，牙齿硬组织的荧光峰值位于480 nm附近；另外在623 nm、685 nm处龋损组织出现较强的荧光峰值，与牙菌斑代谢物质卟啉类化合物的峰位值一致；在405 nm光源激发下牙齿荧光光谱存在明显差异，健康牙齿的荧光图像呈绿色，而龋齿的荧光图像随着牙菌斑含量的增高产生红移。结果表明，通过分析荧光图像颜色差别实现对早期龋齿的检测是可行的。

The main objective of this study is to evaluate the antibacterial effect of antibacterial photodynamic therapy (aPDT) on Streptococcus mutans (S. mutans) biofilm model in vitro. The selection of photosensitizers is the key step for the efficacy of photodynamic therapy (PDT). However, no studies have been conducted in the oral field to compare the functional characteristics and application effects of PDT mediated by various photosensitizers. In this research, the antibacterial effect of Methylene blue (MB)/650 nm laser and Hematoporphyrin monomethyl ether (HMME)/532 nm laser on S. mutans biofilm was compared under different energy densities to provide experimental reference for the clinical application of the two PDT. The yield of lactic acid was analyzed by Colony forming unit (CFU) and spectrophotometry, and the complete biofilm activity was measured by Confocal Laser Scanning Microscopy (CLSM) to evaluate the bactericidal effect on each group. Based on the results of CFU, the bacterial colonies formed by 30.4 J/cm² 532 nm MB-aPDT group and 30.4 J/cm² 532 nm HMME-aPDT group were significantly less than those in other groups, and the bacterial colonies in HMME-aPDT group were less than those in HMME-aPDT group. Lactic acid production in all treatment groups except the photosensitizer group was statistically lower than that in the normal saline control group. The activity of bacterial plaque biofilm was significantly decreased in the two groups treated with 30.4 J/cm² aPDT. Therefore, aPDT suitable for energy measurement can kill S. mutans plaque biofilm, and MB-aPDT is better than HMME-aPDT.

Contrary to the conventional detection method like radiography, the near infrared light source has been demonstrated to be suitable for dental imaging due to different reflectivity among enamel, dentin, and caries lesion. In this paper, three light sources with different bandwidths based on a transillumination method are compared. The contrast among enamel, dentin, and caries lesion is calculated in different situations. The experimental results show that the random fiber laser has the best comprehensive quality in dental imaging due to its high spectral density, low coherence, and deep penetration. This work provides a guidance for light source selection in dental imaging.

Prevention is the most effective way to reduce dental caries. In order to provide a simple way to achieve oral healthcare direction in daily life, dual Channel, portable dental Imaging system that combine white light with autofluorescence techniques was established, and then, a group of volunteers were recruited, 7200 tooth pictures of different dental caries stage and dental plaque were taken and collected. In this work, a customized Convolutional Neural Networks (CNNs) have been designed to classify dental image with early stage caries and dental plaque. Eighty percentage (n=6000) of the pictures taken were used to supervised training of the CNNs based on the experienced dentists' advice and the rest 20% (n = 1200) were used to a test dataset to test the trained CNNs. The accuracy, sensitivity and specificity were calculated to evaluate performance of the CNNs. The accuracy for the early stage caries and dental plaque were 95.3% and 95.9%, respectively. These results shown that the designed image system combined the customized CNNs that could automatically and e±ciently find early caries and dental plaque on occlusal, lingual and buccal surfaces. Therefore, this will provide a novel approach to dental caries prevention for everyone in daily life.

目的：探讨以甲苯胺蓝O(toluidine blue O, TBO)为光敏剂的光动力疗法(photodynamic therapy, PDT)抑制大鼠混合菌生物膜内主要致龋菌作用的影响。方法：以变形链球菌、血链球菌、嗜酸性乳杆菌和粘性放线菌为实验菌株, 建立牙菌斑生物膜模型。实验分为5组, 将40只大鼠随机分配, 8只大鼠为一组:A组用生理盐水处理, 作为阴性对照; B组用洗必泰处理, 作为阳性对照组; C组单纯激光组, 选择波长为630 nm, 应用输出强度为105 mW/cm2, 照射时间为9 min。D组单纯光敏剂组, 光敏剂浓度100 mg/L避光孵育5 min。E组TBO-PDT组, 光敏剂浓度为100 mg/L然后避光孵育5 min后, 应用波长为630 nm, 输出强度为105 mW/cm2进行激光照射。每只大鼠口腔分为4个区, 均选择每区内最后2个磨牙, 每只大鼠共计8个样本牙。平板菌落计数观察牙菌斑生物膜活性, 组织病理切片观察PDT对实验动物口腔软组织的影响。扫描电镜观察PDT作用前后牙齿表面形态的变化。结果: 与生理盐水处理组, 洗必泰处理组相比, TBO-PDT处理组牙菌斑内致龋菌存活的数量( CFU/mL)明显减少(P<0.05),其抑菌率为89.07%; 而C组与D组无明显抑菌效果。扫描电镜显示TBO-PDT组的磨牙表面比较光滑, 脱矿孔表浅。病理切片示TBO-PDT组牙周组织无明显损伤。结论：实验表明光动力疗法有明显的防龋效果, 且对牙体硬组织及牙周组织无明显损伤。