The most generally accepted theory as to the cause of dental caries is that certain bacteria in the mouth, in the presence of fermentable sugars, cause the formation of acids which in turn decalcify teeth. Physicians may help reduce the incidence of caries by recommending elimination of refined sugars from the diet, or at least control of the amount consumed.Cleaning the teeth with a well designed tooth brush after each meal will to a certain extent mechanically remove the fermentable sugar and debris from the teeth. One step further in oral hygiene that may be beneficial is to use a dentifrice with 5 per cent dibasic ammonium phosphate and 3 per cent urea to reduce the formation of acid. Anything that will increase salivation will aid in buffering any acids that may be present.A 2 per cent solution of sodium fluoride applied to the thoroughly dried "intact" enamel surface may prevent caries. Sodium fluoride added to drinking water to a concentration of 1 part per million is utilized by the body in formation of an enamel that is particularly resistant to caries.