Answer: The bacteria uses the oxygen present in the mouth.
Explanation:
The plaque that is formed in the teeth is a highly anaerobic bacteria but it can sustain in the environment rich in oxygen. The oxygen is used by the bacteria and there is a absence of oxygen in the teeth.
It is formed in between the teeth which needs oxygen to survive and if remains for tooth for a longer period of time then it began to grow without oxygen. 
It basically uses the oxygen available in the mouth and makes the condition anaerobic.
 
        
             
        
        
        
<span>Is the study of humankind in all times and places. 
-the study of all humans throughout time and space.                                                                  Hope it helped!</span>
        
             
        
        
        
Parents have many responsibilities to their children, these responsibility must be taken seriously in order to keep the children in the right path. The parental responsibility that I will personally found very interesting is teaching my children how to do different stuffs. Like teaching them cook different dishes and cookies or teaching them to play different games or teaching them funny tricks in mathematics.