Caries: Dental cavities in the two outer layers of a tooth (the enamel and the dentin). Small caries may not cause pain, and may not be noticed by the patient. Larger caries can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins or by foods that are cold, hot, sour, or sweet causing a toothache. Caries are caused by the Streptococcus bacteria, which produces an enamel-dissolving acid as it devours carbohydrate deposits (plaque) on the teeth. To prevent caries, one should brush and floss the teeth daily, use a bacteriocidal mouthwash, and have regular dental cleanings by a professional. If caries do occur, the eroded area can be cleaned and filled by a dentist to prevent further damage.