We are always told to brush daily. We believe that night brushing is not so important. In fact night brushing is more important.

We will know what is the role of night brushing. 

Saliva plays important role in preventing caries because of two things. Flow of saliva and its antibacterial property. 

During sleep, there is less secretion of saliva. So, whatever food particles are there in the mouth stay adhered to teeth without being washed out by saliva. This creates favourable environment for bacteria to produce caries 

Hence brushing before going to bed removes all the food particles from teeth, thus preventing caries