J.R. Blayney

The microbic flora of the dental plaque in relation to the beginning of caries.

The bacterial flora of the oral cavity is one of the most complex to be found in or on the human body. This may be attributed in part, at least, to the variety of environments which may be found in the mouth and to the constant inflow of microorganisms from the air and food. This rich field of investigation has intrigued many workers since the early work of W. D. Miller (1) and a very diverse literature has accumulated. Numerous contributions have dealt with the microorganisms indigenous to the mouth and with changes in the flora related to specific diseased conditions. Most of the reports have been restricted to some part of the flora, usually to a single genus or species. Among those studies having a less specialized viewpoint and making notable contributions to knowledge in this field should be included the work of Kligler on the relationship of bacteria to dental caries (2), of Bloomfield (3) and of Brailovsky-Lounkevitch (4) on the evolution of the oral flora in infants, of Howitt and Fleming on changes in the flora associated with different diets (5) and of Bibby (6) and of Brooke (7) on smears from different areas in the mouth. Little attention has been given by workers in either dental or bacteriological fields to the microbic flora of the dental plaque, in spite of the frequently repeated observation, first made by G. V. Black, that in the earlier stages of the carious process the lesion is always found beneath a plaque composed of bacteria and other microorganisms. These masses are most often found on tooth surfaces which are protected from the normal cleansing mechanisms of the oral cavity and in areas difficult to reach with ordinary dental instruments. The paucity of information in this field of dental research is also partly attributable to the numerous technical difficulties of sampling and cultivation of the small amounts of material available. It seems apparent, however, that a search for the bacterial agent or agents which may be responsible for the earliest stages of the carious process must be made among those microorganisms in and under the plaque. If decay is initiated by local bacterial action the responsible microorganism should be found in plaques covering carious enamel and, conversely, if the relationship is a direct one, should be absent when the surface is found to be caries inactive. Indirect evidence of differences in bacterial flora between caries active and caries free tooth surfaces is found in the work of Stephan (8). He has shown that the pH

Studies on the Different Pathways of Exchange of Minerals in Teeth with the Aid of Radioactive Phosphorus

Walter G. Zoller Memorial Dental Clinic and Department of Anatomy, University of Chicago, Chicago, Ill. The method of tracing a chemical element in tissues of animals by using a mixture of inactive (normal) and radioactive isotopes of this element was introduced by Hevesy in 1935. In the investigation with the new method, Chievitz and Hevesy (1) studied the phosphorus metabolism in bones and teeth. This study and the following by Hevesy, Holst and Krogh (2), Manly, Le Fevre and Bale (3), Hevesy and Armstrong (4) brought about a series of important results concerning the differences in phosphorus metabolism between growing and adult teeth, between their different parts and different tissues. Teeth of rats, cats and human beings were used in these experiments. In our investigation we used the above method in combination with establishing certain abnormal metabolic conditions in teeth. By this procedure we investigated the different possible pathways into and within the tooth. As the conditions established in our experiments are partly identical with conditions occurring either spontaneously in pathological altered teeth or by surgical procedure, the results will help us to understand the changes which occur in tooth metabolism as a result of certain pathological processes. It is clear that there are 3 possible pathways of the metabolism in teeth; namely, through the pulp, the cemento-dentinal junction, and the outer surface of the crown of the tooth. The cementodentinal junction is considered here as a boundary of the tooth. With respect to metabolism, the cementum belongs to the periodontal tissues rather than to the tooth itself because of their common blood supply. Even from the anatomical point of view it may be justifiable

The Evanston Dental Caries Study: II. Purpose and Mechanism of the Study

URING the past few years, public health workers have become interested in the problem of oral disease. It is now generally recognized that tooth decay cannot be controlled by individual treatment. Ways and means must be developed for the control of tooth decay so that entire communities will benefit. Recognizing this need for mass control of tooth decay, the Commissioner of Health of Evanston, Illinois, called a meeting of the dental and medical societies in his community. An advisory committee was appointed to confer with him about the problem of community oral health. Because of the interest shown by the advisory committee in the possible relationship of fluorine to the prevalence of dental caries, Dr. H. T. Dean, Director, Dental Division, United States Public Health Service, was invited to address a joint meeting of the local physicians and dentists on Dec. 11, 1944. After further deliberation of the project, both professional groups recommended to the Commissioner of Health that a carefully controlled study be developed to determine whether or not the addition of fluorine in minute quantities to the communal water supply would reduce the incidence of dental caries in Evanston and Skokie children. The advisory committee and Commissioner of Health then discussed the problem with members of the Walter G. Zoller Memorial Dental Clinic. Because the success of such a program depends upon the enthusiastic support of many different groups, a meeting was held with representatives of each. It was carefully explained to these Evanston citizens that nothing could be promised regarding the ultimate value in the control of tooth decay; that if such a program was to be undertaken it must be in the nature of an exhaustive study; and that it would be several years before data would be available which would even indicate the trend which we might expect. As a result of this meeting, the Evanston City Council on Nov. 5, 1945, passed a resolution authorizing the study and the purchase of the equipment for the addition of sodium fluoride to the eity water. Because the Village of Skokie purchases its water supply from Evanston, a similar resolution was passed by the officials of that community on May 7, 1946. The Director of the Illinois State Department of Health gave his approval; the public and parochial school officials pledged their wholehearted support; and the medical and dental professions endorsed the project. With this imiagnifieant cooperation, the following program was finally evolved.

Further Studies in Mineral Metabolism of Human Teeth by the Use of Radioactive Phosphorus

By the use of radioactive phosphorus it has been demonstrated that an exchange of mineral substances takes place in the enamel of a normal adult tooth (1, 2, 3). In a previous report (3) we have shown that radioactive phosphorus appears in the saliva within 24 hours following intravenous injection and that the intake of phosphorus by the enamel of a normal adult tooth is much greater through the dentin than through the saliva. Even following a traumatic injury to the pulp a day or so before the administration of the radioactive element, we found that the amount of phosphorus entering the enamel from the saliva was negligible when compared with the intake through the dentin. Therefore we concluded that the cemento-dentinal junction served as a major pathway for the supply of the tooth. The purpose of this paper is to report in more detail the mineral intake of human teeth from the saliva and especially to investigate the influence that dental caries may have upon this intake. As a tracer substance, radioactive phosphorus was used. In this investigation it was essential that only the saliva contain radioactive phosphorus, and that the entrance of radioactive phosphorus into the bloodstream be inhibited. Sodium phosphate containing radioactive phosphorus with an activity of about 1.5 m Curies was dissolved in 10 to 12 cc. of water and used as a mouth rinse in order that the radioactive element could be brought into intimate contact with the exposed surfaces of the teeth. After the patient had rinsed the mouth with this solution for a few minutes, 4 teeth were extracted, one of which showed no indication of caries, the other 3 having definite carious lesions. Following extrac-

Comparative Studies of the Feeding of Fluorides as They Occur in Purified Bone Meal Powder, Defluorinated Phosphate and Sodium Fluoride, in Dogs:

Recent interest in fluorine compounds can be traced primarily to the important observations which follow: (a) The presence of 1 part per million of fluorine in drinking water produces a very mild type of dental fluorosis in about 10% of the population if the fluorine is consumed during the period of the calcification of the teeth. On the other hand, the incidence of dental caries is less in communities with water supplies containing certain levels of fluorine. One part per million of fluorine as sodium fluoride will be added to water supplies in at least 3 different American cities to determine if there is a reduction in the incidence of dental caries. (b) Excessive fluorine has been found in phosphatic mineral supplements which are fed to farm animals and added to the soil as a source of calcium and phosphorus. (c) Specially prepared bone flour containing fluorine has been recommended and used to a limited extent as a source of calcium and phosphorus in the diet of children and pregnant women. (d) In the United States, fluorine compounds (cryolite and barium fluosilicate) are used as insecticidal sprays for fruits and vegetables. (e) Fluorides are employed in the studies of the intermediate metabolism of carbohydrates in animal tissues and micro-organisms. General reviews on this subject have been prepared by De Eds (3), McClure (18), Roholm (22, 23), Peirce (21), and Greenwood (13). Publications (7, 8, 9) dealing more specifically with the relation of fluorine to dental health summarize the work of several investigators in this field. Barrentine, Maynard and Loosli (1), Fraser, Hoppe, Sullivan and Smith (10), and Ellis, Cabell, Elmslie, Fraps, Phillips and Williams (5) have recently made nutritive evaluations of defluorinated phosphate as the primary source of calcium and phosphorus in the diet of rats. Bird, Mattingly, Titus, Hammond, Kellogg, Clarke, Weakley and Van Landingham (2) have made a similar study of defluorinated phosphate supplements in the diet of chicks. Shrewsbury and Vestal (24) have reported a comparative study of different phosphate supplements in the

The Evanston Dental Caries Study. XI. The caries experience rates of 12-, 13-, and 14-year-old children after exposure to fluoridated water for fifty-nine to seventy months.

THE dental caries experience rates of Evanston school children, aged 12, 13, and 14 years, indicated a reduction of 12.19 per cent after these children had been exposed to artificially fluoridated water for a period of twentythree to thirty-four months.1 This report on the dental caries experience rates is for children of the same age, presumably influenced by the same conditions, but with exposure time to fluoridated water increased from twenty-three to thirty-four months to fifty-nine to seventy months at the time of dental examination.