In every corner of the world , no space is left where YOU cannot find bacteria in open atmosphere. In our mouth there are many types of bacteria types found but they did not harm us due to the environmental condition of our mouth, some survived, but some cannot. Some survived in acidic condition and some in alkaline , during day time saliva continuously coming and we swallow it again and again and the bacteria present in our mouth goes to our stomach and this helps to prevent tooth from harmful effects of bacteria that is caries, because as we swallow the saliva, the bacteria also swallowed and this process continuously occur ,but during night there is no secretion of saliva and when we eat food, the food get stuck in between teeth and many person, I think almost 90% of the population has not habit of doing brush at night,
so all the problems starts from here, it all helps bacteria to grow because first we give them food and not having habit of brushing, so the bacteria enjoy food and release acids and multiply which demineralised your teeth and this we called as caries and in local language (kida).
only one thing you have to do to keep away yourself from caries and that is only brushing before go to bed at night.
oral health 