CHEMISTRY in DENTAL SCIENCE DONALD A. WALLACE AND HAROLD L. HANSEN American Dental Association, Chicago, Illinois
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HE art of healing, in some form or other, has probably been practiced since the beginning of man's existence. Many of the steps leading to the development of the modern art, and particularly of certain of its branches or specialties, have been taken in comparatively recent times. It is these new accomplishments and trends in the development of the dental division of the healing art which form the basis of this paper. During a major portion of its recently completed century of existence as a separate profession, dentistry grew away from medicine. It became largely a mechanical art. But during this period of time, i t became increasingly apparent that the dividing line between medicine and dentistry is an artificial one; dental conditions are influenced by general physical conditions and vice versa. Therefore emphasis on the biological and biochemical aspects of dnentistty is increasing. Moreover, technical advances in other fields iduence dentistry, as is well shown by the use of the newer resins in the construction of dentures. To all of this must be added the increased need for dental service and especially for the development of an adequate system of preventive dentistry. While dental research receives pitifully inadequate fmancial support, some noteworthy contributions have been made in this field, particularly within the past decade. For the most part, the chemical contribntions have not been made by chemists working in isolation but by chemists warking in c!ose association or cooperation with bacteriologists, physiologists, pharmacologists, clinicians, and others. The complicated nature of oral diseases and the natural limitations of chemists and other scientists as well make such cooperative activities essential. Lack of space prevents an enumeration of the many published chemical studies bearing on dentistry and
dental problems. It should be understood that the following researches which are to be discussed briefly were not chosen as the "best of t h e lot" or as representing the only chemical researches in the dental field. They are, however, typical of what has been accomplished. With adequate support and interest, even more interesting and valuable findings may be anticipated. Hubbell and Bunting ( I ) , in a study of a group of children seven to sixteen years of age, found no definite relationship between the calcidm and phosphorus contents of the saliva and the occurrence of dental caries. More recently, Karshan (2) has reported a statistically significant diierence between caries-free and cariesactive groups in the percentage of calcium removed from the saliva as a result of treating the saliva with tribasic calcium phosphate. Recently these studies have been extended to Alaskan natives. An examination of the results indicates that immunity to caries in these people is associated with the type of diet used, for a change to the white man's diet is accompanied by the development of carious cavities in the teeth. The findings obtained appear to be-valid only for groups and not for single individuals. In other words, neither this test nor others have yet furnished an adequate solution to the problem of individual susceptibility to dental caries. Possibly several factors are involved. Other chemical tests for caries activity, including those based on differencesin rates of acid production in saliva (3) and on diierences in proteolytic power of the saliva ( 4 ) , have been described. Thus it may be seen that chemical methods are being utilized in an effort to combat and conquer one of the most prevalent and destructive diseases of civilized man. It is of more than passing interest and signiiicance to note that our own Chemical Abstracts is the best source of references and abstracts to publications of this nature.
While prevention of dental caries on a large scale has not yet been accomplished, chemical and other scientific findings are of considerable value in this connection. On the basis of these findings, it may be confidently stated that a decrease in the incidence of caries can be brought about by dietary means. Material reduction of highly refined carbohydrates in the diet has been shown to result in a decrease in the rate and extent of the carious process. According to one group of investigators, this may be attributed to the fact that a diet low in these sweet substances does not furnish the required material for acid production by oral microorganisms. Other investigators are of the opinion that the major emphasis should be placed upon the relatively higher proportion of so-called protective vitamins and minerals in such diets. There are indications that both groups may be right. Other means for the prevention of caries have been presented from time to time. Results obtained by the use of strong chemicals and drugs under various conditions have not been encouraging. In a sense there is one exception to this statement; clinical results indicate that ammoniacal silver nitrate (5) is of definite value in arresting incipient dental decay. Under the conditions of professional use, the deposition of silver and silver proteinate from this agent upon enamel or dentin affected by the acids of decay serves to arrest the carious process. Numerous studies on salivary amylase have been reported in the literature. Mayer (6) found that infants, both normal and premature, can digest starch from birth. Meyers and Dellenbaugh (7) devised an improved method for studying the amylolytic activity of the saliva. Some of the individuals studied had low amylase activity during periods of gastric distress. In other cases, there was no apparent relationship between the amylolytic activity of the saliva and various pathological states. Studies relating to chronic endemic fluorosis (mottled enamel) are among the most i n t e r ~ t i n gand striking contributions of chemistry to dentistry. As early as 1913, Gautier (8) demonstrated the presence of fluorides in volcanic rocks and water in Italy where mottled enamel was common. The findings were not, however, related to the incidence of mottled enamel. On the basis of many investigations in this country, McKay (9) postulated that the etiologic factor in mottled enamel was some rare element present in the water supply. In 1925, he persuaded the community of Oakley, Idaho, where the incidence of mottled enamel was 100 per cent, to change its water supply. Eight years later a survey showed that children born after the change in water supply had been made were free of mottled enamel. Subsequent chemical analysis indicated that the old water supply contained six parts per million of fluoride and the new only 0.5 part per million. The relationship between mottled enamel and fluorides in the water supply has been definitely established by a large number of investigations, both chemical and biological.
Research work is never finished. After it had appeared that the investigation of fluorides in relation to dentistry was satisfactorily completed, field studies (10) bearing on the incidence of dental caries in the "mottled enamel" areas were undertaken. The findings indicated that the incidence of dental caries in these areas is lower than in other areas near by where mottled enamel is unknown. Experiments on rats, including biochemical studies, and analytical findings on enamel from sound and from carious teeth also tend to show that fluorides in the diet may be of value in reducing the ravages of dental decay, but not in prrventing it absolutely. Research work in this field is now in progress. No practical applications of the iindings can be made at present. The workers in the field are acutely conscious of the extremely high toxicity of fluorides. To this sketchy outline of chemical researches in the dental field, we must add brief remarks concerning two other items of importance. The newer chemical technics are used in dental research. Chemical discoveries which may appear to be totally unrelated to dentistry are nevertheless of significance and importance. The &st item is well illustrated by two recent publications. In the first of these, Manly and Deakins (11) used microchemical methods to determine the volume, water, organic and inorganic constituents of normal dentin and certain parts of carious dentin lesions. In the second publication, Grossman (12) used the glass electrode to show that aqueous extracts of sound dentin and of carious dentin differ with respect to pH (the mean values obtained were, respectively, 8.16 and 6.51). The second item referred to above is of greater significance than the space devoted to it might indicate. Possibly it can be illustrated, in part, by simply noting as an example that the brilliant researches of Williams and others culminating in the synthesis of vitamin B1 (thiamin hydrochloride) are of ;&erest and importance in dentistry. Vitamin deficiency diseases often have oral manifestations. The dentist often sees these manifestations of deficiency diseases before the patient is aware of them. LITERATURE CITED
(I) HUBBELL AND BUNTING, J . Nzttrition, 5,599 (1932). ( 2 ) KARsnAN, J . Dental Research, 18, 395 (1939). (3) FOSDICK, HANSEN,AND EPPLE,J. Am. Dental Assoc., 24,
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(4) WEINMAN, J. Dental Research, 15,360 (1936). (5) "Accepted dental remedies. 1939." American Dental Association, Chicago, Illinois, p. 198. (6) MAYER,Bulletin of Johns H e k i n s Hospital, 44,246 (1929). (7) MEYERS AND DELLENBAUGH. PVOC. SOC.Ex@tl. Biol. Md., 16, 18 (1918). (8) GAUTIER, C m p t . rend., 157,820 (1913). (9) MCKAY,"Dental wience and dental art" (Chronic Endemic Dental Fluorosis [Mottled Enamel]), Lea & Febiger, Philadelphia. Pa., 1938. (10) "Endemic fluorosis and its relation to dental caries." Public Health Repts.. 53, No. 33 (1938). (11) MANLY AND DEAKINS, J. Dental Rescorch, 19, 165 (1940). ibid.. 19,171 (1940). (12) GROSSMAN,
