Diet is the most significant factor in the development of caries. Carbohydrates and sugars are broken down over different time scales into acids by bacteria in the mouth. These acids demineralise the enamel of the tooth leading to decay. However, saliva contains biochemical complexes that buffer plaque acids and reduce demineralisation. Calcium and phosphate ions contained within the saliva reverse the process of caries formation by remineralising the tooth surface.
The balance of demineralisation and remineralisation processes determines the formation of dental caries. When the tooth is demineralised for prolonged periods then the remineralisation processes are unable to offset the damage caused, leading to the formation of caries. This is illustrated using a Stephan curve where the pH level of plaque is plotted against time (figure 2). When the pH level drops below 5.5 the remineralisation processes can no longer take place. These curves demonstrate how the number of carbohydrate intakes increases the likelihood of caries formation.
Figure 2: Stephan curves showing the pH response in plaque following carbohydrate intake. Left: pH response to a single intake of carbohydrates indicated by the blue arrow. Right: pH response to multiple intakes of carbohydrate indicated by the blue arrows. Note the prolonged period below the critical 5.5 threshold resulting from multiple carbohydrate intakes.