Analysis of Destruction Mechanisms of Dental Biofilm by Laser and Its Clinical Application

牙菌斑是两大牙科疾病--龋病和牙周病的最主要病原。它由细菌细胞及其胞外产物组成，形成了附着在牙齿表面的微生物生物膜。根据牙菌斑到牙周边缘的位置，将牙菌斑分为两部分，即龈上菌斑和龈下菌斑。牙周上菌斑除位于牙间区外，容易去除，牙刷可控制。龈下菌斑位于牙周袋内，如果没有肉眼观察，很难完全清除。在临床上，牙结石也是从牙齿表面清除的主要目标，因为它们的粗糙表面可能是大量牙菌斑的固位体。为了彻底破坏和清除牙齿表面的生物膜和牙石，我们分析了牙科生物膜的微生物活性对化学试剂和生理应激的生理抗性。建立牙科生物被膜模型的评价方法，分析各种清创方法的杀菌效果。其次，分析了利用牙体硬组织的自体荧光特性检测龈下结石的方法。我们发现牙石和牙本质龋在激光刺激下表现出特征性的自发荧光，而健康牙本质和牙釉质则没有。这种方法为我们提供了一种新的非直接可视化的病根表面诊断装置。了解牙菌斑和牙石的生理特性，建立简便、安全、有效的清洁牙齿方法，预防口腔疾病，特别是需要照顾日常生活的老年人。

Dental plaque is the most important etiologic agent of two major dental diseases, dental caries and periodontal diseases. This consists of bacterial cells and their extracellular products and forms the microbial biofilm which adheres sticky to the tooth surfaces. Dental plaque is divided to two parts according to the location to the gingival margin, supragingival plaque and subgingival plaque. Supragingival plaque is easy to remove and to control by toothbrushes expect which is located in interdental area. Subgingival plaque is located inside the periodontal pockets and is difficult to remove completely without visual observation. In the clinics, dental calculus is also major target to eliminate from the tooth surfaces because their rough surfaces are possible retainers of a significant amount of dental plaque. To destroy and to remove dental biofilm and calculus from tooth surfaces completely, we analyzed the physiological resistance of microbial viability of the dental biofilm against the chemical reagents and physiological stresses. We established the assessment method of dental biofilm model to analyze the bactericidal efficiency of various debridement methods. Next, we analyzed the detection method of subgingival calculus by using autofluorescence properties of dental hard tissues. We found subgingival calculus and dentine caries showed characteristic autofluorescence excited by laser irritation, but sound dentine and enamel did not. This method provides us the new diagnosis device for diseased root surfaces without direct visualization. Understanding the physiological properties of dental plaque and calculus, we would established the easy, safe and effective method for tooth cleaning and debridement, to prevent the oral diseases, especially for elderly people who need to care for daily life.