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Prevention of dental caries through salt fluoridation in Mexico

Dra. Lucíla Pazos Hernandez, National Coordinator of the Salt Fluoridation Program in Mexico
On May 27, 1991, Mexico became the seventh country in the world to adopt the salt fluoridation as a mass measure to prevent dental caries. 250 mg of a potassium fluoride compound are added to each kilogram of salt.

The agreement, signed by the Health Secretariat, the Industry and Commerce Secretariat and the Mexican Association of Salt Industries at that date, represented the success of the efforts started in August 10, 1981, when the Regulations concerning the salt fluoridation and iodization were published in the Mexican Official Journal.

The salt fluoridation is one of the main priorities of the Mexican Government, expressed in the 1989-1994 Health National Plan, and is also part of international commitments, such as the 1979 resolutions XXXIX of the Director Council of the Pan American Health Organization, and of the "Cumbre Mundial de la Infancia".

Among the reasons that have influenced the Mexican government decision of adopting salt fluoridation as a prevention of dental caries, we can point out the following:

1. The high occurrence and prevalence of dental caries

Mexico belongs to the group of countries where the prevalence of dental caries is considered high (DMF 4.5 to 6.5 at the age of 12 years), according to the WHO parameters stated in its worldwide epidemiological map.

This phenomenon is significantly less frequent in countries (specially the developed ones) where fluorides are intensive, extensive and continuously used through group and individual preventive actions and programs.

2. The difficulty of using other mass preventive methods against dental caries in Mexico

As it is known, the artificial fluoridation of human consumption water has been, since its beginning in 1945, the most used mass method to prevent dental caries all over the world. It has achieved good results in the decrease of occurrence.

However, in the case of Mexico, several types of difficulties frustrated many attempts to fluoridate water in the main cities. This method benefits approximately only 2% of the population, which are certain sectors of the cities of Mochis, Sin (1964) and Monterrey, N.I. (1971),

where this system was carried out and regularly used.

In the last 45 years, political, administrative, economic and technical difficulties have hindered the use of this measure. We should also consider other relevant aspects such as: the lack of supplying water to the population of the peripheral and rural areas; the poor control of the physical, chemical and bacteriological quality of the water, which has been a decisive factor in the incidence of gastrointestinal diseases (one of the ten major causes of mortality in Mexico), and the regrettable re- incidence of cholera.

3. The great benefit of salt fluoridation

The high effectiveness of salt fluoridation in the prevention of dental caries is comparable to those of water fluoridation in up to 60%, according to the epidemiological evidences achieved through

the use of this measure: Switzerland, in the 50'; Costa Rica, Jamaica and France, 80'; and Colombia, in the present decade.

4. Broad range

The present system of refined (industrialized) salt production and supply in Mexico reaches over 80% of the national population. The remaining population receives marine salt from a great number of small producers, who, at a medium term basis, could prepare themselves to meet the official rules of the Health Secretariat and of the Industry and Commerce Secretariat.

The salt fluoridation and iodization is a unique chance of combining two chemical elements (iodine and fluorine) and thus prevent two important diseases: the endemic goiter and the dental caries, respectively.

Based on the present production level of iodized and fluoridated salt (above 18, 000 tons per month), it is possible to meet the needs of over 70 millions of Mexicans - a range that could not be covered with any other preventive method.

5. The low cost of the measure

Considering the low amount of potassium fluoride required for each kilogram of salt (250 mg), the salt consumption per capita, which is an average of 6.8 g per day, and the low cost of the salt (between 20 and 40 cents), there is no other preventive measure that can be compared to the salt fluoridation economical advantages.

6. Continuity of the program

Due to the agreement signed in May 1991 by the Mexican government and the industrial sector, the program is funded without interfering the finances of the public and industrial sector or the family revenue. This guarantees the continuity of the program - in the medium and long terms-, which is one of the essential conditions to achieve the epidemiological impact that is being pursued.

Technical basis of the Salt Fluoridation National Program

1. Diagnosis and epidemiological vigilance

Aiming at a baseline for the problem of dental caries, from which the effects of salt fluoridation will be measured, the National Survey of Dental Caries in Scholars was performed from 1987 to 1989. The project studied 27 thousand children from ten different states.

Based on the available information, a system of sanitary vigilance will be implemented, to allow periodical studies that will evaluate the behavior of dental caries from the regular supply and consumption of fluoridated salt.

2. Studies on salt consumption

In order to determine the ideal concentration of the potassium fluoride to be added to the salt used by the Mexican population, the Health Institute of Mexico and the National Institute of Nutrition made a research, in 1985, to define both the familiar and the individual daily consumption of salt in urban and rural communities. The socioeconomic status, the variability of the fluoride concentration in the water and the different sources of the salt consumed in those places were taken into account.

3. Studies on fluoride concentration in the human consumption water

A study was performed to investigate the presence of fluoride in the human consumption water in the country. This allowed the exclusion of the states that had optimum and/or high levels of fluoride in their consumption water. These would not receive the fluoridated salt at first. In 1987, the study was updated in all cities with over 10, 000 inhabitants.

In order to successfully implement a vigilance system to investigate the presence of fluoride in the consumption water, it has been necessary to supply laboratories with modern equipment, as part of the services of the Health Secretariat, and to support the training of personnel in the chemical area.

With this infrastructure, it will be possible to conclude, within the year of 1993, the analysis of the fluorine ion concentration in the localities with less than 10, 000 inhabitants,

and also to determine precisely the localities that, due to the high concentration of fluoride in the water, must interrupt the use and sale of the fluoridated salt.

4. Studies of fluoride concentration in human urine

With the purpose of quantifying the adequate level of ingestion and, simultaneously, of the elimination of fluoride in specific groups of the population, the analysis of the

fluoride concentration in the human urine will be made selectively.

The study allows the evaluation of the total quantity of fluoride ingested daily, in order to make sure if the dose is correct for optimum results. The future consumption of salt by the Mexican population must be monitored, since today doctors and nutritionists are inclined to recommend the reduction of salt in the human diet.

5. Quality and sanitary control

In order to assure the homogeneity in the salt quality, salt industries - following the governmental rules, besides their own policies of quality control - are engaged with the quality control of their product, so as to provide an excellent product to be consumed by the population. This product must have the correct dose of potassium iodide, of potassium fluoride and of the compound to prevent humidity.

Moreover, the Health Secretariat is responsible for the surveillance of salt industries and provides randomized samples of the commercialized salt to be analyzed in its laboratories.

6. The exogenous or topic use of other fluorides

As a supplementary measure to the use of fluoridated salt, it is recommended the use of other exogenous or topic fluorides, such as: the use, by scholars, of a 0.2% sodium fluoride rinse each two weeks; the professional use of gel fluorides and/or fluoridated sealants or varnishes; the domestic use of fluoridated toothpaste or solutions.

7. The endogenous or systemic use of other fluorides

The salt fluoridation in our country reduces considerably the indication for the systemic use of other fluorides. These can only be administered to children under one year old, who do not have salt in their diet, or to adults with special diets non-salt diets. The recommendation must be prescribed by a health professional, who will certainly consider the fluoride concentration in the consumption water, besides the age, weight and status of the patients.

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