patient： Nurse ， would you like to tell me something about caries？

　　Nurse： Of course . What do you want to know？

　　P： What causes dental caries？

　　N： It's mainly caused by certain organisms of the oral flora . It is an irreversible ， slowly progressive decay of the hard tissues . It leads to a disintegration of tooth structures and cavitation.

　　P： I wonder if the lesions occus predominantly in particular regions of the tooth（teeth）？

　　N： That's right . It's also connected with the defect of the structure of the tooth（teeth）。

　　P： What is the defect of the structure of the tooth（teeth）？

　　N： It means the dyspasia of the dentine or the uneven squeezingly positioned teeth and the physically defect with sulci and fossae on the teeth.

　　P： How can we prevent this disease？

　　N： The first . it's very important that you pay more attention to the dental hygiene . You should brush your teeth twice a day . once in the morning ， and once in the evening . The upper row of the teeth should be brushed first ， then the lower row . All the crevices must be cleared of remnant food . Besides that . you should rinse your mouth after meals . The second ， take less sweet food ， especially for children . Don't take fermented food before you go to bed or wake up at night ， such as candy or biscuit . The third ， come here for periodical checkups once or twice a year . Caries may progress microscopically a considerable period of time before the lesion can be observed clinically in the tooth strucure . Generally if the cavity is not deep ， you'll have no symptom， so you should have the permanent filling in case that the cavity may get bigger . The fourth ， the methods in using immunization ， laser and coating material to prevent caries are still being carried out in tests . The fifth ， to build up your health is very important.

　　P： It's very kind of you to answer my questions.

　　病人：护士，您能给我讲讲龋齿吗？

　　护士：当然可以，您想了解什么？

　　龋齿是由什么引起的？

　　护士：龋齿是由口腔菌丛中的某些细菌所引起的。它是在牙齿硬组织中发生的一种不可逆的缓慢进行腐蚀过程，导致牙齿组织崩解及腔洞形成。

　　病人：该病变是否主要发生在牙齿的一些特殊部位？

　　护士：晃的，它知牙齿的结构有缺陷有关。

　　病人：什么是牙齿结构上的缺陷呢？

　　护士：那是指牙齿的硬组织发育不良或牙位拥挤，排列不齐，以及牙齿站的沟窝等生理缺陷。

　　病人：如何预防龋齿病呢？

　　护士：第一，注意口腔卫生非常重要。每日应刷牙两次，早晚各一次。先刷上牙，后刷下牙。要把牙缝里的残余食物都刷干净。除此之外，饭后要漱口。第二，少吃甜食，特别是儿童。不要在睡前或半夜醒来时吃可发酵的食物，如糖果、饼干等。第三，定期来这里检查，一年1-2次。在临床上能够观察到牙齿结构病变之前，显微镜下龋齿病的进展可能已持续了相当长的时期。一般龋洞不深时，无任何症状，所以应该早期填充以免龋洞扩大。第四，关于免疫防龋，激光防龋，使用防龋涂料等，现仍在试验阶段。第五，重要的是增进身体健康。

　　病人：非常感谢您给我解答了这么多问题。