Of all the tissues of the body, the dense, glistening enamel which coats the crowns of the teeth is the hardest and most impenetrable. No bone tissue approaches enamel in density. Yet, as most of us know to our sorrow, even the dental enamel is subject to decay; and, what is worse, decay which nature makes not the slightest effort to repair. When any other tissue of the body is destroyed by violence or disease, a more or less successful and wholly spontaneous process of repair sets in, but not so with destroyed enamel. Hence the profession of dentistry.
But what is the cause of caries, or decay? This query introduces one of the puzzles of pathology. At one time caries was attributed to chemical action of acids eructated from the stomach and to acids occurring in the oral cavity. But this notion has been abandoned.
Miller of Germany has probably given the causation of dental caries more study than any one else. And he is probably correct in his belief that the tooth destruction is due to the activities’ bacteria. But his view of the particular way in which the germs affect the teeth is not accepted by other recent investigators. He holds that the bacteria liberate lactic acid and that this acid attacks the enamel and underlying tooth substance.
But a prominent investigator of Harvard University has isolated and studied the behavior of about fifty varieties of bacteria commonly found in decayed teeth, and he reports that only about one-fifth of them produce lactic acid, and that even they do not produce it stronger than one-half of 1 percent – a solution far too weak to affect the teeth. It is curious to note in passing that while Miller in Germany is attributing the decay of one part of the body to lactic acid, Metchnikoff, in France, is attributing the long life of the whole organism to this same acid.
All agree, however, that the accumulations of food particles between and around the teeth favor the development of bacteria and consequent decay. Consequently, whatever the modus operandi of the germs may be, all we have to do — all we can do, rather — is to keep food from between the teeth by the use of floss silk and tooth brush and to restrain bacteria by the aid of mild antiseptic mouth washes.
It has been observed that those teeth least used are more prone to decay. Accordingly the spread of the breakfast cereal may make more work for the dentist. The teeth need exercise to keep healthy.