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"€33 ROLE OF FLUOXIDE I N TOOTH ENAMEL* **

George L. Clark, P11,D.

For the past several years the effect of f luorides i n drinking water on the resistance of t ee th t o decay has been a sub29ct of foremsst in$erest P,o sc i en t i s t s , the public at laxye, and especially parents of gi*owirg children, Convincing s t a t i s t i c a l data dsmnst ra te t';lat i n all csses theye 5s 50 t o 63 per cent smaller incidence of dent a1 cavikisa i n coaziui1ities with fluorfdsted water than i n other camunltles. Medical Association, and other scielnt if i c g r o u p have s1mos.t unanimcusly Fpproved fluoridation. Yet whenever c i t izens have been cal led uron t o vote on the issue, there has been intcnse and bi. t ter oppoSitioila These higkly ercctional aTpeals based on religious c-onv3ctions9 an some insgined loss of freedom cf choice., o r on alleged poisonms ef fec ts of fluorides hme defeated e f for t s t o provide controllsd fluori2at.ion ia perhaps half cf a l l c i t i e s i n which voting on the issue has occurred.

Fk6 Arilerkan Dental Association, the Amrican

It i s surprising t5st fn the debate over f l u o r i h t i o n one of the t r u l y sc i en t i f i c aspects of t he subject hns not been cloarlzr described, c'oes f luoride i n controlled t race amounts in driiW.ng water do t o teeth? Chemistry now has the modern instrumentation by means of which t h i s question may be amwered with posi t ive accuracy. the electron microscope with which linages may be magriifisd 100,000 times o r more, and x-ray and electron d i f f rac t ion a m l y s i s of the s o l i 6 c rys ta l l ine s t ructure of tooth enamel, dentine, and bone, Leme no doubt conceriiing the effect of controlled f luoridat ion of drinking water, Research work with these precision instruments has been successfully conducted and st i l l continues with intensif ied e f for t i n mazy laborator ies , but e s p c i a l l y at the Xational Bureau of Standards, the National In s t i t u t e s of Xealth, the New York University Coilege of Dentistry, and the Chemistry Department of the University of Illinois. The resu l t s a r e concordant and highly conclusive. Only the b r i e fe s t summary of some of the most d i rect and important find-ings a r e possible here.

Exactly w h a t

Improved opt ical microscopic techniques,

"Presented before the Champaign County, I l l i n o i s , Torch Club. Published i n "The TParchR (January 1958), the o f f i c i a l per iodical of the International Association of Torch Clubs, alld the edi tor of Torch." **G. fie Clark has been research professor of ana ly t ica l chemistry at the University cf I l l i n o i s since 1953, having headed the divis ion of analyt ical chemistry f o r twenty-six years. D.Sc., 1937) and of the University of Chicago (PhbDa, 1918), honorary societ ies including Phi Beta Kappa and Sigma X i , he has received the Marburg Lecture Award of the American Society f o r Testing Materials, the Grassel l i Medal of the Society of Chemical Industry, and the Mehl Medal of the Congress of Metals, He has served the American Chemical Society as chairinan of the Division of Physical and Inorganic Chemistry (1928) and as chairman of the Division of Cellulose Chemistry (1939)

Reprinted with the kind Termission of the author

9e i s a graduate of DePauw University (Al Be, 1914; honorary A menber of several

Dr . Clark tras editor-in-chief of the Chemical Encyclopedia (Reinhold, 1957) and senior author of Quantitative Analysis, 1952.

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The careful measurements and identifications of minerologists have contrib- uted the essential background f o r the analysis of the effect of f luoride upon tooth enamel, which i s 96 per cent inorganic mineral. protective layer on teeth is identical with the well known calcium phosphate mineral, hydroxyapatite, which chemists describe by the formula C a l O (P04)6 (OH)z, where C a is calcium, PO4 i s phosphate and OH is the basic hydroxyl group (which, combined with hydrogen, yields water, E20). proved repeatedly by x-ray d i f f r a c t h n patterns, which are characterist ic "f inger-printslf of the unique composition and structure of each crystal l ine solid. and existing i n foods i n t o t h i s phosphate i n teeth and bones from the ear l ies t embryonic stage of development. developed i n l iving processes has proved that the basic hydroxyl gro-qs i n th i s compound which readily react with acids may be replaced s t a t i s t i c a l l y and a t random i n the crystal l a t t i c e by fluoride ions without i n any way affecting the structure of the apat i te ; hydroxyapatite now becomes fluorapati te, The fluoride ions are just a l i t t l e smaller than the hydroxyl groups which they replace, so that the crystal l a t t i c e i s tightened s l ight ly , a6 shown by a s l ight sh i f t i n the l ines on the c r p t a l pattern. A neasurabl-e increase i n hardness and a decrease i n solubi l i ty of the mineral and the tooth enamel may actual ly be detected when one out of each 300 hydroxyl groups i s replaced with f luo r i d e .

This crystal l ine

This f a c t has been

lihus the hman body i s able t o build the minerals dissolved i n water

Laboratory analysis of teeth hnd bones

This amount of f luoride i n enamel, corresponding t o only 0.013 per cent by chemical analysis, is the equilibrium concentration result iag from the presence of 1 part per million of f luoride i n drinking watero logical processes of the hman body, t h i s trace amount of f luoride is trans- ferred from water t o the blood plasma and i n turn is bui l t into the teeth of in fan ts before eruption, When hydroxyapatite mineyal o r t o Q t h enamel is placed i n a solution of a fluoride, the exchange of f luaride foi. hydroxyl by diffusion is exceedingly slow except at elevated temperatures, It is clear, then, that the most beneficial effect of fluoride is brought about by introduction during the early stages of tooth formation and deposition of the mineral matter on a network OL very f i n e organic f i b r i l s during the development of the embryo. This i s prove6 by study of the teeth of infants and children before and a f t e r tooth eruption.

In the physio-

Fluoride plays an exceedingly important role in addition t o i t s substitu- On the average, tooth enamel contsins 3*98 per cent t ion i n hydroxyapatities.

carbonate that is not uniformly distributed i n the apa t i te but segregated i n localized areas, gas is well known. react with acids i n the foods and in the mouth t o form the beginnings of the lesions which result i n dental caries. amounts completely eliminates these carbonate areas, so that there is no chance f o r acid reaction. f t is not surprising, then, that i n a l l communities w i t h controlled fluoridation of water supTlies there is on the average a 60 per cent decrease in the incidence of dental car ies , especially in children.

The reaction of acids on carbonates t o produce carbon dioxide This seems t o be the cause of "soft spots," which readily

Fluoride in even these very small

There are a number of other effects of f luoride on dental enamel, as well as those on dentine, which is 70 per cent apa t i te mineral, and those on cementum on r o o t s of teeth, which is 50 per cent apati te. For example,

hydroxyapatite is converted at a relatively low temperature to another calcium phosphate mineral compound, whitlockite, with an entirely different structure, Such a change, if allowed to occur, could be a highly disruptive process in teeth and bones. In the presence of tracsri of fluoride in the apatite, this transformation temperature ie raised to above 6000: thus fluoride has a remarkable stabilizing and preserving effect.

Electron microscopy, one of the great new tools of science, shows at high magnifications the structure of tooth enamel with remarkable clarity, In new erupted teeth (baby and second teeth) the solid, crystalline matter of enamel possesses a marvelously regular and organized structure of extremely minute hexagonal prisms fitting together like mosaic tiles. of parallel bands on the surfaces called perikymata, which resemble the over- lqping shingles on a roof.

There is also a series

In normal cases without fluoride these structures disappear rapidly as the developing child masticates more or less abrasive foods and uses dentifrices with polishing and abrasive action, indefinite structure, sometimes with prominent scratches. But with fluoride the evidence of hexagonal prisms and perikymata persists for many years, indicating greater stability, hardness, and resistance to solution or abrasion.

Microscopic examination shows only an

In areas where the natural water supply contains 5 or more parts of fluoride per million, the familiar mottling of teeth occurso the formation in some areas of calcium fluoride imbedded in the apakite mineral. These teeth suffer only in appearance, for they are very hard and resistant to decay.

This seems to be due to

Calcium fluoride in layers only a few molecules deep is also formed on enamel surfaces by the use of tooth pastes containing tin fluoride (fluorostan), which reacts with calcium in the hydrox#yaptite, and of course covers up the highly reactive carbonate spotso These layers, aasily reformed, have a protective effect because calcium fluoride is the well known inert insoluble mineral fluoride. to a hundred times as much fluoride without deterioration of tooth structure; the fluoridea give strength and hardness t o teeth with sharp needle points.

It is interesting t o note that sharks have teeth with fifty

The exact mechanism of fluoridation effects on teeth has thus been scientifically demonstrated. phosphate mineral of teeth, not as a separate concentrated phase, preclude8 the possibility of any poisonous effects which may be associated with large doses of sodik fluoride or similar compounds. traoe amounts, the fluoride remains permanently as an effective barrier to tooth decay.

Fluoride widely distributed in the essential

Once present in enamel in these

Tnfrared Spectrometry Shows How

In a paper just published, Professor Robert B. Pischer of Indiana University describes his great success in applying infrared spectrometry to the proof of the mechanism of fluoridation on tooth enamel. This technique now is probably the most rapid and depermiable method far determining the actual percentage of fluorine in the crystal lattice as a function of the concentration of fluoride in water supplies.

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Research in crystal chemistry, then, with the aid of such instruments a8 optical and electron microscopes, x-ray and electron diffraction, emission spectrographic analysis and infrared absorption spectraphotometry, has given an unequivocal answer as to why and how very small amounts of fluoride in drinking water seem always to be associated with greatly decreased tooth decay. to ascertain the truth and acceptance of the facts instead of rumors and propaganda, another milepost on the road to ever improving national health will be passed.

With understanding of the unprejudiced efforts of research scientists

TXE LEGALITY aF THE FLUORIDATXOH PROCEDUB* *+ Bernard J. Conway, LL.3

Political scientists and lawyers will be reviewing the cmrt decisions on fluoridation long after public acceptance of the fluoridation procedure has put to rest the claims now being made by its opponents, Those who have con- tributed their efforts, and perhaps considerable financial resources, toward the disposition of fluoridation litigation may not f u l l y appreciate their gracious offering to political science and legal learning. At this moment in fluoridation's short history no one can criticize a failure to recognize that the significance of the fluoridation cases goes beyond securing bet,ter health for the nation's citizens, This public health goal should be and is uppermost i n the zealous efforts of those who have undertaken responsibility for defend- ing the fluoridation procedure in the courts,

I shall, then, contribute what I can to an understanding of the legal principles which apply to the right of a municipality or other subdivision of a state to initiate fluoridation. sketch of fluoridation's contributions to political science and legal learning.

I have no goal other than to present a

- m e Authority of f4unicipality: The city, the town, the village are creatures of the state in which they are located. may be broad or limited. One must look to the municipality's charter from the state and other state laws to determine its powers, Under our federal system each state has retained to itself the full measure of police power, federal government, at least theoretically, has no police ;power.

Their govesnmental powers

The

*Presented at the Conference on Fluoridation sponsored by the Indiana State Dental Association and the Indiana State Board of Health, Indianapolis, Indiana, October 2 , 1957.

**Secretary of the ADA Council on Legislation.