BEST PROSTHODONTIST IN ANNA NAGAR! Streptococcus mutans, also known as S mutans, along with lactobacilli, consume sugars and excrete lactic acid. It’s the lactic acid that is the real culprit when it comes to tooth decay. S mutans and other bacteria reside on the dental biofilm (plaque) on tooth surfaces. The acid they produce from consuming sugar causes demineralisation, softening that area of the tooth, leading to a loss of calcium and phosphate from the enamel. As the enamel on a tooth surface loses minerals, the weakened enamel collapses to form a cavity and the tooth is progressively destroyed. The acid can also attack the roots of teeth should they become exposed from gum recession.