Tooth decay causes enamel and dentine to gradually weaken. It begins when acids are formed by bacteria acting on sugars that soften or demineralize the enamel. Bacteria in the mouth create acids after eating through the oxidation of sugar and food particles in the mouth. Tooth decay starts when the mouth’s pH is below 5.5.
In addition to food particles, masses of bacterial cells bind to the teeth to form dental plaque. Since plaque coats the teeth, saliva can not reach the tooth layer to neutralize the acid. Upon eating brushing the teeth removes the plaque before acids are formed by the bacteria.
The primary focus should be on decreasing the bacterial load in the mouth if you want to prevent tooth decay. Brushing and flossing remove on the teeth (plaque) the sticky bacteria accumulation. When used with brushing and flossing, an antimicrobial mouth rinse (such as Listerine or Scope) is effective at reducing bacteria in the mouth.