Fluorine and Dental Caries in New Zealand.
A brief review of the physiology and pathology of fluorine has been published in N.Z. Dent. J., 43, 5, 1947. Dean et al. (1942) found an inverse relation between the fluorine content of the potable water supplies (where less than 1 ppm. F.) and the incidence of dental caries (Pub. Health Rept., 57, 1177, 1942). In New Zealand, the fluorine content of the water supplies is less than 0.5 ppm. F., and is thus below the threshold value for protection against dental caries. (Chamberlain, G., N.Z. J. Sc. Tech., 26, 90, 1944; ibid., 28, 155, 1946; Denmead, C. F., ibid., 28, 159.) Preliminary analyses of the enamel and dentine of New Zealand teeth indicate that the fluorine content is low compared with the results of overseas workers. From X-ray crystal analyses of enamel and dentine, it is seen that fluorine occupies an integral position in the main apatite lattice. These findings indicate that fluorine may be a factor in the high incidence of dental caries in New Zealand. It is therefore necessary to test this hypothesis. There are many ways that this may be attempted, as, for example, by the studies of the effect of the fluorination of the water supplies on the incidence of dental caries, of the effect of the daily ingestion of small amounts (e.g., 1 mg.) of fluorine during the calcification of the teeth, and of the effect of the topical application of fluoride solution on to the erupted surface of teeth.
So it is hoped, with the co-operation of dentists, of chemists, and of all those who are concerned with the high incidence of dental caries, on the above and other lines we may determine whether or not fluorine is a factor in the incidence of dental caries in New Zealand.
Dr. R. M. S. Taylor opened the discussion, mentioning that H. B. Younger had recently written of Dental Caries as primarily a bacterial invasion of the “organic roads” of the enamel, the prism sheaths, spindles and lamellae. This offers an explanation for the partial immunity following development of permanent teeth where the drinking water contains optimum amounts of fluorine. He suggests that this “developmental or pre-eruptive immunity” does not affect
the lamellae so that they are open to invasion after the tooth erupts unless they with the sheaths are subsequently blocked against invasion. This may come through calcium salts in the saliva blocking the organic entrances, i.e., “naturally acquired” immunity, but that possibly some unknown factor differentiates-immune from susceptible persons. Finally, an “artificially acquired” immunity may be produced by impregnating the tooth surface with drugs which producean insoluble deposit which completely seals the organic entrances against bacterial invasion. This is the field of topical applications, as with fluoride or silver nitrate. The success of this treatment depends on “correct diagnosis” involving Bacillus acidophilus counts and control, and, at least temporarily, on control over the carbohydrate intake.
Miss Harrison, referring to fluorine analyses of New Zealand drinking water, had mentioned that the Raglan Dairy Company's bore had a fluorine content approaching the optimum. When in charge of the School Dental Clinics in that area he (Dr. Taylor) had tried to find children who had had water from the Raglan bore during the tooth developmental period. However, most homes around Raglan have their own water supply—usually from tanks, whilst the dairy bore supplied a very small area. He had not been successful in locating children who might have shown the effects of taking that water over a reasonable period.
The lecturer in Preventive Dentistry in Sydney had stated that his experimental group of dental students appeared to have received benefit from fluorine mouth washes, and that encouraging results had followed their work with topical applications of fluoride.
As regards fluorising the New Zealand water supplies, considerable amounts of fluoride would be needed, and this might be a difficulty.
Mr. Field stated that superphosphates used for fertilisers in New Zealand contained 2–4% of fluoride, which had to be extracted before use. The Nauru phosphates contained 2 ½% fluoride which now went to waste. If the fluoride was needed, this could be obtained cheaply and easily.
Dr. Hubert Smith referred to the taking of bone-meal by mouth as an alternative to fluorinating the water supply, if this proved difficult to inaugurate. Even if only 50% of the fluorine present in the bone-meal were available on absorption, as mentioned by Miss Harrison, it would appear simpler and easier to provide bone-meal tablets or powder containing enough added fluorine for the needs of children during the tooth-forming period, and only those children actually prepared to use them need be given them, thus ensuring the best use of the available material. This type of medication might avoid the troublesome three-monthly visit to the dentist for meticulous cleansing prior to painting with. 2% sodium fluoride. An easy oral method would be more likely to come into widespread use, and would be more likely to be kept up, than one involving considerable time and trouble both by patients and by dentists, who could not at present cope with such work on the scale really necessary.