Dear Dr. Ellie,
Can you talk a little about tooth bacteria? I know that the human mouth is full of it – but I have also heard that there is good bacteria in the mouth. What causes cavities and what is harmless?
Simon S, Pinellas Park, FL
First, there are small round bacteria that are harmless. These bacteria quickly attach even to newly cleaned teeth. After about 8 hours, small groups of these bubble-shaped bacteria form into clusters. From about 8-12 hours, more clusters form and join together. After 12 hours these become tubular in shape. And at around 15 hours the bacteria crowds the tooth surface. More of these tubular bacteria grow and line up perpendicular to the tooth surface and more bubble-shaped bacteria hang on the ends of the longer bacteria, (yuck!)
This builds up and the layers of bacteria covers each other. In the deeper layers, an oxygen shortage develops. Certain bacteria adapt to this oxygen shortage and become anaerobic. These are the cavity-forming bacteria that form the acids that damage teeth. (And that is where things get bad).
So these bad-bacteria begin to damage the teeth and make the whole mouth acidic–making more bad bacteria.
After about 24 hours, the bacteria crowd the tooth surface and begin to form layers of plaque. (Plaque is a blanket of acidic bacteria in a sticky mesh that attaches to the teeth).
So there is the quick lesson on mouth bacteria. I hope this helps explain things!