DENTAL CARIES CONTROL WITH DENTIFRICES AND MOUTH WASHES 285 cation of the sugar (10). The dental plaques in caries immune cases do not rapidly ferment sugars (11, 12). THE CONTROL OF DENTAI. CARIES On the basis of the above, it is obvious that if the acid decalcification is the cause of dental caries, one should be able to control dental caries by simply preventing the formation of acid or by making the tooth more re- sistant to the effects of acid. Today, every method of caries control that has been effective has utilized one of the above methods. The restriction of dietary sugars prevents dental caries very nicely (13, 14). This method prevents the formation of acid by eliminating all substances from the mouth that may form acids. A similar process has been very effective in animals. Concentrated sugar diets when fed to animals in the normal manner will produce rampant caries (15). When this same diet is given by stomach tube, no dental caries results (16). The use of enzyme inhibitors which will prevent acid formation has also been found effective in the control of both animal and human caries (17, 18). Certain antibiotics that destroy the microbial flora have also been successful in the prevention of dental caries (19-21). The ingestion of fluoride in drinking water or the topical application of fluorides render the tooth more resistant to acids. Both of these methods have been found effective in control of dental caries (22, 23). SOME FACTORS CONTRARY TO THEORY Even though it has been definitely shown that the prevention of acid formation in the plaque and the decrease in solubility in enamel will defi- nitely decrease caries activity in humans and animals, there are a number of factors that have been observed which do not conform to the theory. It has been demonstrated that when refined sugar is made available to a population, dental caries increases materially. On this basis it is thought that natural sugars are not particularly cariogenic while refined sugars are. It is known that fruits and fruit juices generally contain around 10 per cent sugar. The sugar is generally sucrose, the same sugar that is most widely ingested in the refined form. Fruits and fruit juices are not ordinarily considered cariogenic even though they do contain considerable quantities of fermentable sugar. If fermentable sugar is the cause of dental caries, why then does the simple act of refining it make it cariogenic? It is not changed chemically. Furthermore, in most fruits and fruit juices certain vitamins and minerals which act essentially as co-enzymes or activators for the glycolytic enzymes are present, thus making fruit juices more sus- ceptible to fermentation, than pure sugar solutions. On this basis fruit juices should be much more cariogenic than refined sugars, for without the activators, no fermentation occurs. There must be some explanation for this paradox.

286 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Another factor that is rather coniCsing is that most fruit and fruit juices particularly those of the citrus variety, have acid potentials that vary fkom pH 2.0 to 5.0. If acids are the cause of dental caries, then these acid solu- tions when taken into the mouth should cause decalcification regardless of the sugar content. It has been demonstrated many times that most citrus fruit juices will readily decalcify teeth, yet it has been shown many times that citrus and other fruits are not cariogenic. Under some circumstances, the teeth have been known to erode when acid fruits are held in contact with them for long periods of time, but no cariou's lesions are produced. Before the present-day theory of dental caries can be fully established, this paradox must also be explained. It has been demonstrated many times that the inorganic portion of the tooth is rather constant within narrow limits. The inorganic portion of the deciduous tooth is essentially the same as tha.t of the permanent tooth. It has been shown repeatedly that a deciduous tooth will decay more rapidly than a permanent tooth. It has also been shown that a young permanent tooth is much more susceptible to dental caries than an old permanent tooth. It is generally believed that if dental caries can be prevented until a person is t•venty-five years of age, few cavities will normally form after this age. If the composition of the tooth is essentially the same, whether the tooth is deciduous, new, old or young, unless there is a marked change in environ- ment, there should be little difference in the rate of decay. If the inorganic portion of the tooth is the first portion that is dissolved in the initiation of a carious lesion, then in so far as the inorganic portion does not change, ease of solution should remain constant. This is not the case. The experiments of Kite (16) adequately demonstrated that when the sugars of a cariogenic diet are fed to rats via stomach tube no carious lesions developed. However, in all of the experiments in which substances that would prevent fermentation were incorporated into the cariogenic diets, even though caries activity was reduced, some lesions always developed. In most cases the sugar inhibitor mixtures would not ferment in vitro. Hence we must assume that either the sugar per se had some effect or under the conditions that prevail in the mouth, some fermentation did take place and some acid did form. The fact that dental caries does develop with non- fermentable sugar mixtures requires some explanation. On the basis of recent investigations logical explanations for the above discrepancies have been made available. These new data may also explain why control measures to date have been only partially successful and may furnish clues for new approaches to the entire problem of caries control. PERMEABILITY OF THE TOOTH The enamel shell appears to be nonvital, it does not regenerate when it