There are several factors that all contribute to tooth decay. One the formation of visible biofilm on the teeth called plaque. The bacteria in plaque breakdown sugar from the patient's diet by fermentation to an acid called lactate or lactic acid. The acid lowers the pH at the surface of the tooth where plaque is attached to the tooth. The low pH (5.5 or less) causes the enamel to demineralize. If the pH is at 5.5 or lower for long periods of time damage to the enamel results in dental caries.