Should We Use Milk Fluoridation? A Review1 RODRIGOMARI~~O~ This article presents the argument that becauseof several demonsfrafed advantages, milk fluoridation provides a valid alternative to water fluoridafion when the latter is not possible. Extensive literature describing study of fl uoride compounds adminisfered with calcium-rich food, as well as clinical trials and laborafo y experimen fs with fluoridated milk, have dem- onstrated its effectiveness in caries prevention. The main criticisms of milk fluoridation are decreased bioavailabilify of the fluoride, the cost and adminisfrafive burden involved, and (in some cases) lack of sound clinical conclusions regarding ifs preventive efficacy. These S criticisms are reviewed in fhe light of evidence now available. he World Health Organization has Indeed, oral health surveys have shown T recommended specific goals for oral that in most countries of the Americas health by the year 2000 (I). Among other about 95% of the population has a history things, these goals assert that the de- of dental caries (2). If countries continue cayed, missing, and filled teeth index to rely on programs based on dental caries (DMFT)3 at 12 years of age should be 3 treatment rather than prevention, we or less. In 1990, only 5 of 38 countries cannot expect major improvements in this and territories in Latin America and the picture, especially since there are many English-speaking Caribbean (the Baha- places where a significant part of the mas, Cuba, Dominica, Guyana, and Saint population lacks access to reguIar oral Lucia) had such a DMFT index, while 8 health care. Clearly, a different approach countries had DMFT indices exceeding to the problem must be found. 6.5 (2). Thus, although most countries of Dental caries is a preventable infec- the Americas have significantly im- tious disease caused by bacteria that ac- proved the health conditions of their peo- cumulate in dental plaque. Fermentation ple, oral disease continues to be a highly of common dietary carbohydrates by these prevalent health problem. plaque bacteria leads to formation of acids that cause loss of minerals from the tooth enamel, a process that ultimately pro- ‘This article will also be published in Spanish in duces cavities. Scientific knowledge in- the Boletin de la Oficina Snnitnrin Pnnnmericnrra, Vol. dicates that dental caries can be pre- 120, No. 2, February 1996. Reprint requests and vented by measures that include use of other correspondence should be sent to the author fluorides and fissure sealants, removal of at the following address: School of Dental Science, dental plaque, and reduction of ferment- University of Melbourne, 711 Elizabeth Street, Mel- bourne, Vie 3000, Australia. able carbohydrates. 5chool of Dental Science, University of Melbourne, The mechanism by which fluorides Melbourne, Australia. prevent dental caries has been studied 3The DMFT index is the arithmetic average of the for over 50 years and is now accepted as number of teeth (T) that are decayed (D), missing safe and appropriate (1, 3-6). Fluorides (M), or filled (F) as a result of caries occurring in permanent dentition. The DMFS index uses the are absorbed through the gastrointestinal tooth surfaces as the unit of study. The equivalent tract, with a rate and degree of absorp- indices for temporary dentition are dmft and dmfs. tion that depends on several elements Bzrlletin of PAHO 29f44),1995 287 (7). After entering the plasma, fluorides These methods provide protection against are either deposited in the bone or de- caries that rivals that provided by fluor- veloping teeth, or else they are removed idated water. In addition, studies have by the kidneys and excreted in the urine. shown that fluoride provided through During tooth formation, fluoride is in- other alternative methods can effectively corporated into each tooth’s mineralized prevent caries (16), such methods includ- structure, providing increased resistance ing use of fluoride solutions or gels top- to demineralization by organic acids. ically applied and fluoridation of sugar After a tooth erupts, systemic fluorides and various beverages including milk (4, no longer play a role in its formation. 5, 9, 17, 28). However, when consumed systemically All these alternatives involve some dis- they are excreted through the saliva and advantages that any country must con- can provide surface protection for the sider within the context of its particular tooth throughout its lifetime (8, 9). This local, regional, or national needs when posteruption effect is responsible for de- deciding what is the best method to em- creased demineralization when teeth are ploy. Such deliberations have led to a exposed to acids and for increased rates variety of conclusions about the merits of of remineralization (10). Fluorides also af- water fluoridation alternatives. Within that fect bacterial metabolism and act in other context, this article reviews scientific data ways to reduce potential tooth enamel on milk fluoridation and analyzes com- destruction (5, 9, II). peting theses in the current debate on The great mass of evidence now avail- the subject to help resolve the question able indicates that a 50-65% reduction in of whether milk fluoridation should be dental caries indices can be achieved by used. To do this, it describes the basic adjusting the fluoride content of unfluor- rationale for using milk as a fluoride ve- idated drinking water to optimal levels hicle and discusses the main objections (0.7 to 1.2 mg/L) (I, 5). However, polit- to milk fluoridation in the light of cur- ical, administrative, geographic, and rently available data. technical factors have commonly pre- cluded drinking water fluoridation, de- RATIONALE FOR THE USE OF nying this benefit to a large part of the MILK FLUORIDATION world’s population (1.2). This lack of a fluoridated water supply From a public health standpoint, the is not an insuperable barrier to receiving community water supply is regarded as the benefits of fluorides. For instance, in the most effective fluoridation vehicle (3, some places where people could not be 27, 19). In the 1980s the International reached by public water supplies, coun- Drinking Water Supply and Sanitation tries have tested and implemented alter- Decade strongly promoted provision of native community-based fluoridation water supply services to the population. programs at the local, regional, or na- Nevertheless, despite efforts made in the tional levels. Various methods-includ- Americas to provide water for all by 1990, ing salt fluoridation (in Colombia, Costa in that year approximately 12% of the Rica, France, Germany, Hungary, Ja- total urban population still lacked house maica, Mexico, Spain, Switzerland, and connections, and in rural zones this pro- Uruguay-Z, 4, l3-25), school water portion was much higher, on the order fluoridation, distribution of fluoride tab- of 45% (20). lets, and use of fluoride mouth rinses (in According to several researchers (2l- the United States-4, 5, l6)-have been 25), when a water supply is not available employed by public health programs. milk should rank first among the alter- 288 Bulletin of PAHO 29(d), 1995 native fluoridation vehicles. After water, fluoride in community fluoridation pro- milk is considered the most important grams if it reached the right people. In contributor to total fluid intake (26-28). accord with the need to find solutions It is also an important food for pregnant appropriate for local conditions (34, 35), women, infants, and children during the it would be particularly valuable in rural period of tooth formation (4, 22, 29, 30). areas, where the population is unlikely Like salt, milk does not require a com- to have access to appropriately fluori- munity water supply system, and so it dated water. can reach communities lacking this serv- Other authors, however, have con- ice and can enable people to have free cluded that milk is not an appropriate choice regarding their fluoride intake. Like vehicle for fluoridation (17, 35-37). Our certain other alternatives, it imposes no review of these criticisms has indicated major administrative burdens on teachers four major areas of concern, these being (23, 31) such as those imposed by pro- (1) decreased bioavailability of sodium grams using fluoride mouth rinses or fluoride (NaF) when ingested with foods supplements at school, nor does it create rich in calcium such as milk (38-40), (2) a need to ensure compliance (8). Indeed, cost (36, 37), (3) administrative burdens an adequate level of compliance (an ad- (production, delivery, storage and distri- equate intake of fluoridated milk) might bution problems) relative to other meth- be assured if fluoridated milk were needed ods (17, 36, 37), and (4) lack of definitive for its nutritional as well as its cariostatic conclusions from clinical trials (28,35,37). value, or if children were expected or re- quired to drink it when provided (32). Ericsson (21), Poulsen et al. (22), Villa BIOAVAILABILITY et al. (32), and Toth et al. (33) have proven that fluoride does accumulate in calcified In the case of fluorides, bioavailability tissues following ingestion of fluoridated is defined as the percentage of a given milk. Ericsson, who administered F as fluoride that is absorbed, reaches the cir- NaF to rats, reported that femoral F up- culation, and is available for use by the take from milk was about 80% of that living organism (7,23,42,42). It therefore from water, and that a tooth’s retention depends on the amount of free forms of of F paralleled that of the skeleton at a fluoride present (7). Hence, any factor comparable stage of growth. Animal ex- that decreases free fluoride levels will de- periments conducted by Poulsen et al. crease bioavailability (7). (22) found increased fluoride levels in rat It is well known that concomitant in- enamel after administration of fluori- take of food and beverages may reduce dated milk.