Salt fluoridation--an alternative in automatic prevention of dental caries.

Despite great improvements in terms of reduced prevalence and amount of dental caries in populations worldwide, problems still persist particularly among the underprivileged groups of both developed and developing countries. Research and practical experience gained in several countries have demonstrated however, that dental caries can be prevented effectively through establishment of fluoride programmes. Water fluoridation, salt fluoridation, milk fluoridation and use of affordable fluoridated toothpastes play the major roles in public health. The present paper outlines the relevance and some practical aspects in relation to implementation of salt fluoridation programmes. The World Health Organisation Oral Health Programme provides technical assistance to countries in the process of planning, implementing and evaluating salt fluoridation projects.

Changes in dental caries 1953-2003.

In the first half of the 20th century, indices and methods of conducting surveys of the level of dental diseases were developed. Modern epidemiological studies began in the fifties and many reliable studies have been conducted after 1960. In the following decades, a substantial decline of caries prevalence was documented in the majority of the highly industrialized countries, with reductions of lifetime caries experience exceeding 75%. The decline comes to an end when low or very low levels of prevalence are reached. Children of low socioeconomic status and immigrants from outside Western Europe, however, generally have higher disease levels and may cause increases in caries prevalence. For this and other reasons, caries epidemiology will remain an indispensable part of dental public health.

Successes and drawbacks in the caries-preventive use of fluorides--lessons to be learnt from history.

Water fluoridation was the first breakthrough in the practice of preventive cariology on a community level and has remained one of the cornerstones of prevention in dentistry. The concepts regarding the mechanisms of the caries-inhibitory effect, however, have changed in several respects. Today there is general agreement that topical effects on the erupted enamel are most important. The contention that there is no pre-eruptive effect whatsoever has created confusion; there is in fact evidence for a minor pre-eruptive protective effect. Around 1980 many experts believed that fluorides should not be used in high concentrations, for instance above those in dentifrices, because this could block remineralisation in the body of pre-cavity lesions. However, it is now known that such undesirable effects are negligible or non-existent. In the fifties and sixties, fluoride tablets were widely used in Europe and helped to make the concept of caries prevention popular. From 1980 onwards, fluoride dentifrices were found to have a much greater impact and were recognized as being able to lead to a decline of caries prevalence in entire countries, and fluoride tablets gradually lost their importance. Antifluoridationists were unable to delay or hinder the widespread use of fluoride toothpastes but in many cases have successfully opposed public health measures such as fluoridation of water or of salt. The spread of these methods, beneficial for all social strata, might have been more rapid if some of the experts had not propounded the erroneous supposition that fluoride dentifrice will be sufficient for caries prevention. Sale of fluoridated salt has been authorized in several countries on a nationwide scale. However, only Latin American countries have introduced salt fluoridation for entire populations. In Central and Eastern Europe where caries prevalence continues to be high and where the level of usage of topical fluorides including dentifrices will presumably remain at a low level for many years, salt fluoridation would be beneficial.

[Decline of caries prevalence in Swiss military recruits between 1970 and 1996]. / Rückgang der Kariesprävalenz bei Schweizer Rekruten von 1970 bis 1996.

In 1996, 416 military recruits (aged 20.4) were dentally examined. The mean DMFT based on clinical findings was 4,8 (including extracted premolars). The mean DMFT based on clinical and radiological findings was 5.3 (DT=l.2; MT=0.4: almost all of them premolars; FT=3.7. 13% of the recruits were caries-free (DMFT=0). On average, 8.7 affected sites (DFS) were counted; 1.4 were untreated (DS). The caries declined by 70% (DMFT) between 1970 and 1996 and by 46% (DMFT) and 54% (DFS) respectively between 1985 and 1996. In the latter period of time, the mean number of untreated lesions (DS) decreased by 71%, in approximal surfaces of molars and premolars even by 78%. The ratio FS/DFS was 51% in 1985 and 71% in 1996,. This means an improvement in restorative care. 56% of all DFS were found in pits and fissures, 36% in approximal surfaces of molars and premolars. 62% of all untreated lesions (DS) were observed in approximal surfaces of molars and premolars; this percentage was 83% in 1985. The estimated caries increment between age of 15 and 20 was approximately 1.6 DFS/year in the early eighties and 1.3 DFS/year in the early nineties. In 1996 , the former difference in caries prevalence between the recruits from the Canton of Vaud and those from other Western Cantons did not persist. This is probably due to an alignment of the nation-wide supply with fluoridated salt since 1983.

Urinary fluoride excretion by children 4-6 years old in a south Texas community.

This study evaluated urinary fluoride excretion by school children 4-6 years old who were living in a south Texas rural community that had concentrations of fluoride in drinking water supplies generally around the optimal level. We took supervised collections of urine samples in the morning and afternoon at school, and parents of the participating students collected nocturnal samples. We recorded the beginning and end times of the three collection periods and then determined the urinary volume and urinary flow for each of the periods. We measured urinary fluoride concentrations and calculated the urinary excretion rate per hour. The children had breakfast and lunch provided at the school, where the drinking water contained 1.0-1.3 milligrams/liter (mg/L) fluoride. Fluoride concentrations in the tested household water supplies, from wells, ranged from 0.1 to 3.2 mg/L fluoride. The children's average urinary fluoride concentrations found for the day were similar to those for the night, with means ranging from 1.26 mg/L to 1.42 mg/L. Average excretion was 36.4 micrograms/h in the morning, 45.6 micrograms/h in the afternoon, and 17.5 micrograms/h at night. The lower nocturnal excretion rates are easily explained by low urinary flow at night. Based on the 15 hours of urine collected, the extrapolated 24-hour fluoride excretion was 749 micrograms. In conjunction with similar studies, the data from this study will help in developing upper limits for urinary fluoride excretion that are appropriate for avoiding unsightly fluorosis while providing optimal protection against dental decay.

The prevalence of dental caries in Europe 1990-1995. ORCA Saturday afternoon symposium 1995.

Caries prevalence data from recent studies in all European countries showed a general trend towards a further decline for children and adolescents. However, in several countries with already low caries prevalence in primary teeth, there was no further decrease. Regarding the permanent dentition, further reductions were observed in the 12-year age group, these being even more evident at the ages of 15-19 years. In some Central and Eastern European countries, caries prevalence in children and adolescents was still high. Few data were available on young adults, but the benefits of prevention are becoming manifest. The available data on the use of toothbrushes, fluorides and other pertinent items provided few clues as to the causes of the decline in caries prevalence.

Water fluoridation results in Basel since 1962: health and political implications.

The population of the canton Basel-City has been provided with fluoridated water since May 1962. This paper presents a summary of basic findings from evaluations of this public health intervention. Standard methods were used for assessing dental caries, enamel fluorosis, urinary fluoride, and other data. Caries prevalence of schoolchildren declined until 1977 because of water fluoridation, after which it continued to decline until the late 1980s due to reasons other than water fluoridation. Caries prevalence in Basel was at least as low as in those other parts of Switzerland where either school-based dental health education programs or comprehensive salt fluoridation programs had been implemented for many years. Enamel fluorosis was seen in 38 percent of the children, similar to regions with comprehensive salt fluoridation, but higher than in low-fluoride regions. Overlap of salt and water fluoridation in families consuming both fluoridated water and fluoridated salt has occurred, but has not resulted in problems. Fluoride concentrations (close to, but mostly below 1.0 ppm) and excretions (0.45-0.80 mg F per day in children, around 1 mg in adults) corresponded to expected levels. Statistics from both the School Dental Service and the Public Dental Clinic indicate a dramatic reduction in the amount of conservation dentistry being done and, in adults, prosthetic services. Political steps to remove water fluoridation were taken in 1976, 1982, 1989, and 1993, but have not been successful. Water fluoridation has resulted in the expected benefit and continues to exist beside salt fluoridation used in the other cantons of Switzerland.

[The dental health of permanently resident schoolchildren in 16 Zurich rural communities in 1992]. / Zahngesundheit von daueransässigen Schülern in 16 Zürcher Landgemeinden im Jahre 1992.

Between 1964 and 1992, caries prevalence (DMFT) of permanently resident school children in 16 communities in the Canton of Zurich decreased by 85 to 87%. In the ten- to fourteen-year-olds, the reduction amounted to 25-29% in the period of 1988 to 1992. In 1992, the fourteen-year-olds had only 1.90 DMFT and 2.49 DFS, the average DS being 0.28. The 21% children with the highest caries experience showed only 9 DFS on average. Such a low caries activity does not favour positive cost-benefit results for individual intensive prevention. From 1964 to 1984 caries prevalence in primary teeth of 7-year-old children decreased to the level of 1.81 dmft; the further reduction to 1.55 dmft in 1992 was not significant. Few primary molars were lost prematurely. According to a saliva-test, 59% of the children aged 10 to 12 with high concentrations of mutans streptococci were free of caries; by comparison, 80% of the children with the lowest mutans-test value, were free of caries. In spite of the easy availability and the multiple usages of fluorides (dentifrices with either 250 or 1000-1500 ppm F, domestic salt, gels with 12,500 ppm F and rinsing solutions with 230 ppm F since 1986-88), only 16% of the children showed signs of dental fluorosis.

Urinary fluoride excretion in Jamaica in relation to fluoridated salt.

The purpose of this study was to compare the urinary fluoride levels in subtropical Jamaica just before the beginning of salt fluoridation (250 mg/kg salt) in 1987 and again 20 months later. Four age groups were studied in three locations with low to intermediate fluoride concentrations in the drinking water. The averages of supervised, timed morning fluoride excretions ranged between 12.1 and 27.9 micrograms/h prior to fluoridation as compared with 23.7-67.4 micrograms/h 20 months after the beginning of the sale of fluoridated salt. The fluoride excretions obtained from 24-hour collections ranged from 169 to 485 micrograms/24 h in 1987 and increased to 304-657 micrograms/24 h in 1989. In 1987, the morning fluoride excretions approximated those of French and Swiss children who had a low fluoride intake, but the fluoride levels of 1989 were similar to the data obtained from children who had an intake of 1.2-1.7 mg F/day or consumed fluoridated water.

Urinary fluoride excretion in children with low fluoride intake or consuming fluoridated salt.

The purpose of this study was to compare urinary fluoride excretion with fluoride ingestion in children who had either a low fluoride intake or received supplemental fluoride through salt or water. The urinary samples were collected in two ways. In procedure A, urine was collected in the morning, at noon and during the afternoon. This covered a continuous period of approximately 7 h from the beginning to the end of the school day. In procedure B, morning, afternoon and night samples were collected. The morning and afternoon samples were obtained under supervision at school. Procedure B was more useful than procedure A for monitoring salt fluoridation projects. Children with a history of low fluoride intake excreted a mean of 10 micrograms F/h during the night and the morning, but 13-16 micrograms F/h after the main meal. Children in a water-fluoridated town or in comprehensive salt fluoridation programs excreted between 19 and 33 micrograms F/h. However, after the intake of meals prepared with fluoridated salt (250 ppm F) the mean excretion of fluoride ranged between 31 and 49 micrograms F/h. The levels of excretion corresponded with the levels of fluoride intake and meal patterns in the various groups.

[Caries occurrence in schoolchildren of the canton of Glarus in 1974 to 1992: the effect of the use of fluoridated salt]. / Kariesbefall bei Schülern des Kantons Glarus in den Jahren 1974 bis 1992: Wirkung der Salzfluoridierung.

Between 1974 and 1976, fluoridated salt (250 ppm F) was introduced in the Swiss Canton of Glarus and has been used since by the bakeries and most households (domestic salt) in the Canton. Caries prevalence in schoolchildren of this Canton declined from 1974 to 1992 by 80 to 85%. As an example, 12-year-old children had 6.5 DMFT in 1974, but only 1.1 in 1992. In 1992, most DF sites were fissures and pits and most of them filled. Caries prevalence in primary teeth (dmft) decreased by 49 to 66% in the age groups 7, 8 and 9, and most of the reduction had occurred before 1983. In 1974, the average fluoride concentration in urine amounted to 0.36 ppm; between 1979 and 1992 it increased from 0.74 to 0.86 ppm. 46 to 60% of the bread samples contained between 3 to 9 ppm F; this bread had obviously been produced with fluoridated salt. Salt fluoridation contributed to caries decline until up to 1987, while subsequent caries reductions in permanent teeth must have been caused by other factors. In comparison to other Swiss data the caries prevalence of pupils in the Canton of Glarus was low in 1992.

[The dental status of schoolchildren from abroad in Canton Zurich 1992 to 1994]. / Zahnzustand von aus dem Ausland zugezogenen Schülern, Kanton Zürich 1992 bis 1994.

Between 1992 and 1994 DMF-experience was determined in several hundred schoolchildren from the City of Zurich and 16 small communities distributed over the whole Canton. Immigrants were distinguished from permanently resident children with respect to their length of residence. Children who had arrived after the age of 5 or 6 (kindergarten-age) showed higher caries prevalence; e.g., at the age of 12, 2.00 (16 communities) and 3.14 (City of Zurich) as compared to 1.13 and 1.24 DMFT. Children in special classes for learning German, who had arrived from former Yugoslavia the year before, had 3.64 DMFT at the age of 12. All the children, whether Swiss nationals or non-citizens, who were integrated into the school dental service of the City, had satisfactory treatment levels. In contrast, recent immigrants from former Yugoslavia had about half of their diseased teeth unfilled and often badly destroyed. Therefore, fortnightly tooth-brushings were introduced as a first measure to lower caries activity.