Abstract

INTRODUCTION

Dental caries and its consequences continues to be a public health problem in many low and middle income countries and for socially disadvantaged groups in high income countries. However, the incidence and prevalence of dental caries has decreased significantly over the last few decades, especially in the young, an evident protective effect which can be attributed to the widespread use of fluoride.

The first research into the use of fluoride concentrated on its collective use in drinking water. Such research aimed not only to measure the preventative effects on the prevalence and incidence of dental caries, but also to establish safe levels in order to avoid dental fluorosis. ¹³13 . Frazão P, Peverari AC, Forni TIB, Mota AG, Costa LR. Fluorose dentária: comparação de dois estudos de prevalência. Cad Saude Publica . 2004;20(4):1050-8. DOI:10.1590/S0102-311X2004000400020
https://doi.org/10.1590/S0102-311X200400... ^{, 16}16 . Jones S, Burt BA, Petersen PE, Lennon MA. The effective use of fluorides in public health. Bull World Health Organ. 2005;83(9):670-6. DOI:10.1590/S0042-96862005000900012
https://doi.org/10.1590/S0042-9686200500... Systematic reviews of the literature of the last decade reaffirm the importance of using fluoride to prevent dental caries and recommend balancing the risks and benefits of collective and individual use of fluoride (topical use of fluoride). ¹⁴14 . Holloway PJ. Systematic review of public water fluoridation. Community Dent Health. 2000;17(4):261-2. ^{, 19}19 . Parnell C, Whelton H, O’Mullane D. Water fluoridation. Eur Arch Paediatr Dent. 2009;10(3):141-8. ^{, 27}27 . Yeung CA. A systematic review of the efficacy and safety of fluoridation. Evid Based Dent. 2008;9(2):39-43. DOI:10.1038/sj.ebd.6400578
https://doi.org/10.1038/sj.ebd.6400578...

Dental fluorosis is defined as a change in the mineralization in the tooth enamel due to prolonged intake of fluoride during the period in which the teeth develop. ¹1 . Aoba T, Fejerskov O. Dental fluorosis: chemistry and biology. Crit Rev Oral Biol Med . 2002;13(2):155-70. DOI:10.1177/154411130201300206
https://doi.org/10.1177/1544111302013002... ^{, 2}2 . Beltrán-Aguilar ED, Barker L, Dye BA. Prevalence and severity of dental fluorosis in the United States, 1999-2004. NCHS Data Brief . 2010;(53):1-8. The majority of cases reported in the literature, including in Brazil, indicate mild or very mild occurrence of fluorosis which is, therefore, not considered to be a public health problem. ³3 . Cangussu MCT, Narvai PC, Castellanos Fernandez R, Djehizian V. A fluorose dentária no Brasil: uma revisão crítica. Cad Saude Publica . 2002;18(1):7-15. DOI:10.1590/S0102-311X2002000100002
https://doi.org/10.1590/S0102-311X200200... ^{, 7}7 . Cypriano S, Pecharki GD, Sousa MLR, Wada RS. A saúde bucal de escolares residentes em locais com e sem fluoretação das águas de abastecimento público na região de Sorocaba, São Paulo, Brasil . Cad Saude Publica . 2003;19(4):1063-71. DOI:10.1590/S0102-311X2003000400028
https://doi.org/10.1590/S0102-311X200300... ^{, 12}12 . Forte FDS, Freitas CHSM, Sampaio FC, Jardim MCAM. Fluorose dentária em crianças de Princesa Isabel, Paraíba. Pesq Odontol Bras. 2001;15(2):87-90. DOI:10.1590/S1517-74912001000200002
https://doi.org/10.1590/S1517-7491200100... ^{, 13}13 . Frazão P, Peverari AC, Forni TIB, Mota AG, Costa LR. Fluorose dentária: comparação de dois estudos de prevalência. Cad Saude Publica . 2004;20(4):1050-8. DOI:10.1590/S0102-311X2004000400020
https://doi.org/10.1590/S0102-311X200400...

Dean ⁸8 . Dean HT. The investigation of physiological effects by the epidemiological method. In: Moulton FR, editor. Fluorine and dental health. Washington (DC): American Association for the Advancement of Science; 1942. p.23-31. (Publication 19). describes the most commonly used method of clinically and epidemiologically classifying dental fluorosis. At the end of the 1970s, increased knowledge of the histological and microscopic characteristics of dental fluorosis enabled new methods of classification to be developed, among them the Thylstrup and Fejerskov index, ²⁴24 . Thylstrup A, Fejerskov O. Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes. Community Dent Oral Epidemiol . 1978;6(6):315-28. the Tooth Surface Index of Fluorosis (TSIF), ¹⁵15 . Horowitz HS, Driscoll WS, Meyers RJ, Heifetz SB, Kingman A. A new method for assessing the prevalence of dental fluorosis: the Tooth Surface Index of Fluorosis. J Am Dent Assoc . 1984;109(1):37-41. and the fluorosis Risk Index. ²⁰20 . Pendrys DG. The fluorosis risk index: a method for investigating risk factors. J Public Health Dent. 1990;50(5):291-8. Selecting the appropriate index depends on the aim of the study, but the use of different indexes to establish the presence of fluorosis is a problem for the reliability and consistency of data on prevalence/incidence.

The SBBrasil 2003 ( Condições de Saúde Bucal da População Brasileira - Oral Health Conditions in the Brazilian Population) and the Pesquisa Nacional de Saúde Bucal (Brazilian Oral Health Survey - SBBrasil 2010) are two nationwide surveys into oral health carred out in Brazil, and dental fluorosis was one of the health problems investigated. The SBBrasil 2010 was primarily an oral health monitoring strategy based on producing primary data, aiming to reinforce National Oral Health Care policies based on an epidemiologically based health care model.

The aim of this study was to analyze the limitations of the study of dental fluorosis in cross-sectional surveys.

METHODS

A quantitative based study with a descriptive and analytical approach, with data from the SBBrasil 2003 and SBBrasil 2010 studies. Based on this analysis, aspects of the reliability of the data obtained in the two surveys were discussed, as well as the accuracy of the estimates.

The data from the two above mentioned surveys were obtained from data bases available in the Brazilian Ministry of Health’s General Coordination of Oral Health website. First, the database from the 2003 and 2010 databases were combined in order to analyze trends. The variable “year” was created in order to distinguish between the two databases and the final database had a total of 146 thousand records. Some of the variables were present in the 2003 survey and not in the 2010 survey, and vice-versa. In this case, if the variable was deemed to be important in the analysis, it was kept in the database and given a zero code in the year in which it did not appear. This was the case, for example, of the weighted variables which were only used in 2010.

As there were no weighted variables in 2003, the confidence intervals were calculated assuming a simple causal sample. In 2010 the confidence intervals were calculated taking into account design and weighting variables. Details of the sample design and the teams’ training process for both surveys can be found in other publications. ^aaMinistério da Saúde (BR), Secretaria de Atenção à Saúde, Departamento de Atenção Básica. Projeto SB Brasil 2003: condições de saúde bucal da população brasileira 2002-2003: resultados principais. Brasília (DF); 2005. (Série C. Projetos, Programas e Relatórios). ^{, b}bMinistério da Saúde (BR), Secretaria de Atenção à Saúde. Projeto SB Brasil 2010 - Pesquisa Nacional de Saúde Bucal. Brasília (DF); 2009.

The index proposed by Dean ⁸8 . Dean HT. The investigation of physiological effects by the epidemiological method. In: Moulton FR, editor. Fluorine and dental health. Washington (DC): American Association for the Advancement of Science; 1942. p.23-31. (Publication 19). was used in the investigation of dental fluorosis in 12-year-old children. The outcome variable, the presence of fluorosis, was analyzed with a normal condition being considered based on a combination of “normal” and “questionable” scores and the other categories composed the prevalence of fluorosis, following the rules recommended in the 2003 and 2010 studies.

The distribution of the prevalence of fluorosis was shown according to the domains of the study (state capitals and regions) and the year studied (2003 and 2010). The confidence intervals (95%CI) were also shown for simple prevalence (without considering severity).

The data were analyzed using the SPSS version 17 statistics program. The first analysis of the data was conducted at an individual level (by year and by domain) and the behavior of the trend showed discrepancies and atypical observations.

In order to analyze the discrepant data (higher and lower), the following cutoff points for the prevalence of fluorosis were established, with the minimum being from close to zero to 1.4% and the maximum being values above 30%, defined based on estimates of the prevalence of fluorosis for cities with and without fluoridated water. In cities where the water is not fluoridated there was expected to be a minimal prevalence of fluorosis due to exposure to fluoride from other sources, as well as genetic variations and individual variations in fluoride intake. Accordingly, cities with fluoridated water and regular control did not show a prevalence of fluorosis above 30%, even when other sources of fluoride are considered. ⁹9 . Denbesten P, LI W. Chronic fluoride toxicity: dental fluorosis. Monogr Oral Sci. 2011;22:81-96. DOI:10.1159/000327028
https://doi.org/10.1159/000327028...

Taking into account that there is a degree of imprecision inherent to the index used, the occurrence of random or systematic error ispossible. ⁵5 . Costa AJL, Nadanovsky P. Validade na pesquisa odontológica. In: Luiz RR, Costa AJL, Nadanovsky P, organizadores. Epidemiologia e bioestatística na pesquisa odontológica. São Paulo: Atheneu; 2005. p.125-41. This imprecision may be due to characteristics particular to the index or linked to deficiencies in the training and instruction process.

Therefore, in order to investigate the source of the error, the municipalities with the highest rates of prevalence in 2010 were analyzed, separating the values by census tract. Each examiner was responsible, on average, for three census tracts so that, when analyzed in isolation, the data could indicate bias in one or more examiners or, conversely, show that there was uniform bias between all of them.

Another aspect analyzed concerns the ideal sample size to be used in studies of the prevalence of fluorosis. The sample size for the 12-year-olds was calculated so as to estimate, with reasonable precision, rates of prevalence above 20%. ^ccMinistério da Saúde (BR), Secretaria de Atenção à Saúde. Projeto SB Brasil 2010 - Pesquisa Nacional de Saúde Bucal. Brasília (DF); 2009. In general, the expected prevalence for fluorosis is well below this, so that, in order to obtain a good estimate “n” needs to be increased. Therefore, simulations were carried out aiming to estimate the minimum sample size necessary to observe the prevalence of fluorosis with more appropriate intervals of confidence. For this simulation, the expression given by the formula (1) was considered, in which the calculation of standard error includes design effect (d).

The SBBrasil 2010 Project followed the standards set by the Declaration of Helsinki and was approved by the National Council on Research Ethics, record no. 15,498, 7 ^th January 2010.

RESULTS

Table 1 shows the distribution of rates of prevalence of fluorosis according to the domains of the study (state capitals and regions) and year (2003 and 2010). The 95%CI are also shown for simple prevalence (without considering severity).

Taking 2003 as the base year, Palmas (61%) in the North, Belo Horizonte (42%) in the Southeast and Curitiba (45%) in the South stand out. The prevalence in Palmas, for example, is so high that it caused the mean for the North (where fluoridated water supplies are scarce) to approach that of the South East (where all of the state capitals add fluoride to tap water).

Lack of fluorosis, or very low values should be viewed with caution, especially if the municipality provides fluoridated drinking water. This is the case in Florianópolis and Rio de Janeiro in 2003, with rates of prevalence of 1.05 and 1.4% respectively. On the other hand, Maceió, without a fluoridated tap water, had a prevalence of 16.3%.

Figures 1 and 2 show the data from Table 1 from different perspectives. Figure 1 shows prevalence ordered by year, with considerable variance in the prevalence, from 0% to 61% in 2003 and from 0% to 59% in 2010, highlighting those state capitals with atypical values, either for being very low (no fluorosis or, maximum 1.4%) or very high (over 30%).

Figure 2 shows the prevalence of fluorosis and respective 95%CI according to region and year. Figure 3 shows percentage difference between 2003 and 2010, with the former as the base year. Thus, positive numbers indicate an increase and negative number a decrease in prevalence.

In 2010, there appeared to be greater coherence between the prevalence of fluorosis and fluoridated water: municipalities without this had lower percentages. However, when the data for 2003 and 2010 are compared (Figure 3), the inconsistencies become evident. There were variations ranging from -100% in Boa Vista, in other words, fluorosis of 6.25 literally disappeared in 2010, to 1,540% (15 times higher) in Florianópolis, where fluorosis of 1% in 2003 climbed to 16.4% in 2010. In four state capitals with fluoridated water supplies (Palmas, Curitiba, Macapá and Brasília) there was a reduction in the prevalence of fluorosis between 2003 and 2010 and in five state capitals where the tap water is not fluoridated (João Pessoa, Cuiabá, Porto Velho, Manaus and Natal) increases between 74% and 210% were observed.

The data in Table 1 and Figure 1 show that, although the rates of prevalence seem to vary greatly between state capitals in terms of percentage points, these largely disappear when the interval estimates are considered. When the values for the prevalence are ordered as shown in Figure 1, it is possible to identify four groups of state capitals in which the prevalence does not vary statistically: (a) Rio Branco, Recife, Boa Vista, São Luís, Natal, Porto Velho, Cuiabá, Maceió, Macapá and João Pessoa, with rates of prevalence varying between 0% and 8%; (b) Manaus, Rio de Janeiro, Fortaleza, Palmas, Curitiba, Campo Grande, Brasília, Florianópolis and Teresina, with values between 8.7% and 17.7%; (c) Porto Alegre, Goiânia, Vitória, Aracaju and Belém, varying between 18.6% and 26.6%; and (d) São Paulo, Salvador and Belo Horizonte, with rates of prevalence between 37.3% and 58.6%.

When analyzing the prevalence of fluorosis and considering the distribution of the tracts in the state capitals, it can be observed that in one of the municipalities, where the general prevalence was 27%, almost all of this percentage (21%) was located in 1/3 of the 30 assessed tracts, for which the data were obtained by five examiners. When data considered to be outliers and pertaining to these examiners were excluded the prevalence fell to 6.7%. On the other hand, in another municipality, there was no concentration of high prevalence in any tract. In half of the tracts the values were above the mean (58%) and variation between the examiners was not considered to be significant.

Table 2 shows standard errors and 95%CI for estimates of prevalence based on different sample sizes for a design effect equal to 2. Taking a minimum coefficient of variation of 15% as the parameter for decision making, as in the SBBrasil 2010, the minimum sample size would be1,500 individuals and the confidence interval between 3.4% and 6.6%.

DISCUSSION

In general, it is possible to infer that there is no rationality behind fluorosis trends in Brazil. Small variations may be acceptable, bearing in mind that strategies for controlling fluoride in the water may vary between state capitals.

However, these data may indicate, fundamentally, the validity of the data themselves, in other words, an epidemic prevalence (61%) in Palmas is inconceivable. In Belo Horizonte there seemed to be logic in terms of the trend, but the values are very high in both years, even for a city which adds fluoride to the water. The same is true, to a lesser degree, of São Paulo. The case of Salvador is emblematic, with an increase from 7.6% in 2003 (an acceptable value for a city which adds fluoride to the water) to 44.3% in 2010. Finally, there is no explanation for the case of Florianópolis in which, although the value for 2010 was not that high, it represented a 15 fold increase. In these municipalities there are no records of significant alterations in the tap water or of increases in the sources of fluoride which justify such marked changes.

The definition of fluorosis and the methodological considerations necessary for its clinical and epidemiological diagnosis are significant, given the subjectivity of the classification. Examinations for dental fluorosis may contain more variations than those carried out for other oral health conditions. ²¹21 . Pendrys DG. Analytical studies of enamel fluorosis: methodological considerations. Epidemiol Rev. 1999;21(2):233-46. The difficulties in diagnosing and characterizing milder cases of fluorosis may be caused by the presence of opacity in the enamel not due to fluoride. It is possible that there is confusion in the differential diagnosis between milder forms of fluorosis and opacities not caused by fluoride. ¹¹11 . Fejerskov O, Manji F, Baelum V, Moller I. Fluorose dentária: um manual para profissionais de saúde. São Paulo: Editora Santos; 1994.

Moreover, the diversity of the indexes proposed to measure fluorosis, combined with the need for rigorous training for the examiners and the lack of a standardized and less subjective method have been highlighted as the causes of difficulties in comparing studies on the evaluating trends in prevalence, ²⁶26 . Whelton HP, Ketley CE, McSweeney F, O´Mullane DM. A review of fluorosis in the European Union: prevalence, risk factors and aesthetic issues. Community Dent Oral Epidemiol. 2004;32(Suppl 1):9-18. DOI:10.1111/j.1600-0528.2004.00134.x
https://doi.org/10.1111/j.1600-0528.2004... and is a problem for the reliability and consistency of the data.

Various studies measuring fluorosis have been carried out using the Dean index, or variations of the Dean and other indexes, ³3 . Cangussu MCT, Narvai PC, Castellanos Fernandez R, Djehizian V. A fluorose dentária no Brasil: uma revisão crítica. Cad Saude Publica . 2002;18(1):7-15. DOI:10.1590/S0102-311X2002000100002
https://doi.org/10.1590/S0102-311X200200... ^{, 13}13 . Frazão P, Peverari AC, Forni TIB, Mota AG, Costa LR. Fluorose dentária: comparação de dois estudos de prevalência. Cad Saude Publica . 2004;20(4):1050-8. DOI:10.1590/S0102-311X2004000400020
https://doi.org/10.1590/S0102-311X200400... ^{, 17}17 . Mabelya L, Hof MA, Konig KG, Palenstein Helderman WH. Comparison of two indices of dental fluorosis in low, moderate and high fluorosis Tanzanian populations. Community Dent Oral Epidemiol. 1994;22(6):415-20. ^{, 18}18 . Mohamed AR, Thomson WM, Mackay TD. An epidemiological comparison of Dean’s index and the Developmental Defects of Enamel (DDE) index . J Public Health Dent. 2010;70(4):344-7. DOI:10.1111/j.1752-7325.2010.00186.x
https://doi.org/10.1111/j.1752-7325.2010... ^{, 22}22 . Pereira AC, Moreira BH. Analysis of three dental fluorosis indexes used in epidemiologic trials. Braz Dent J. 1999;10(1):29-37. showing various discrepancies and limitations to the use. ²¹21 . Pendrys DG. Analytical studies of enamel fluorosis: methodological considerations. Epidemiol Rev. 1999;21(2):233-46.

New research has been developed out in order to establish new methodologies and protocols in epidemiological surveys, ²³23 . Soto-Rojas AE, Martinez-Mier EA, Ureña-Cirett J, Jackson RD, Stookey GK. Development of a standardisation device for photographic assessment of dental fluorosis in field studies. Oral Health Prev Dent . 2008;6(1):29-36. aiming to improve diagnosis using photographs. Some studies ⁶6 . Cruz-Orcutt N, Warren JJ, Broffitt B, Levy SM, Weber-Gasparoni K. Examiner reliability of fluorosis scoring: a comparison of photographic and clinical examination findings. J Public Health Dent. 2012;72(2):172-5. DOI:10.1111/j.1752-7325.2012.00315.x
https://doi.org/10.1111/j.1752-7325.2012... ^{, 18}18 . Mohamed AR, Thomson WM, Mackay TD. An epidemiological comparison of Dean’s index and the Developmental Defects of Enamel (DDE) index . J Public Health Dent. 2010;70(4):344-7. DOI:10.1111/j.1752-7325.2010.00186.x
https://doi.org/10.1111/j.1752-7325.2010... conclude that the method using photographs is more reproducible and reliable than clinical examinations and can be used to diagnose dental fluorosis.

Among the limitations of this study, the difficulty of working with two databases constituted from different sample designs and different training procedures stand out. The teams for the SBBrasil 2010 received training using slides with photographs of various stages of fluorosis, so-called training in lux, ^ddMinistério da Saúde (BR), Secretaria de Atenção à Saúde, Departamento de Atenção Básica, Coordenação Nacional de Saúde Bucal. Projeto SB Brasil 2010 – Pesquisa Nacional de Saúde Bucal: manual de calibração de examinadores. Brasília (DF); 2009. whereas in the SBBrasil 2003 the training followed the traditional method. However, the intra and inter-examiner concordance values for the kappa statistic were not divulged in either situation.

Thus, depending on the training process and the characteristics of the examiner, it is possible that the examiners overestimated (Palmas in 2003 and Belo Horizonte in 2010) and underestimated (São Luís) fluorosis. This seemed to occur even in different years (in 2003 and in 2010), as in the example of what happened in Palmas (prevalence dropped to 11% form 60%) and in Florianópolis (where there was an increase from 1% to 16.4%).

The discrepancies between the SBBrasil 2003 and the SBBrasil 2010 data are even more pronounced when independent studies published in the literature are introduced for comparison. For example, Aracaju, with a prevalence of 7.8% in 2003 and 25.4% in 2010. In an independent study ⁴4 . Carvalho RWF, Valois RBC, Santos CNA, Marcellini PS, Bonjardim LR, Oliveira CCC, et al. Estudo da prevalência de fluorose dentária em Aracaju. Cienc Saude Coletiva. 2010;15(Supl 1):1875-80. DOI:10.1590/S1413-81232010000700101
https://doi.org/10.1590/S1413-8123201000... in Aracaju of 196 schoolchildren aged between five and 15 who underwent an oral examination using the Dean index found an 8.16% prevalence of dental fluorosis.

Another important aspect concerns the estimative power, a fundamental question in establishing the statistical significance of the differences (between years, regions and domains, for example). In addition, the confidence interval of the prevalence is a population estimate and indicates the precision of this value in estimating the true parameter.

The interval estimate is calculated considering standard error and, therefore, is a function of the sample size itself. Thus, low values of prevalence would have the same standard error for a specific sample size so that the effect is proportionally greater. ²⁵25 . United Nations, Department of Economic and Social Affairs, Statistic Division. Household sample surveys in developing and transition countries. New York; 2005. (Series F, 96). The lower the prevalence value the greater the proportional interval for a given sample.

In the SBBrasil 2010 the sample of 12-year-olds considered an ideal coefficient of variation (ration between standard error and prevalence) to be below 15%. This means that, for an expected sample of 250 children, a reasonable power of precision can only be observed for rates of prevalence above 20%. From the point of view of methodological choice, this is because of the fact that the sample size considered dental caries as the reference health problem. ^eeMinistério da Saúde (BR), Secretaria de Atenção à Saúde. Projeto SB Brasil 2010 - Pesquisa Nacional de Saúde Bucal. Brasília (DF); 2009. Although other health problems were assessed in the SBBrasil 2010, a considerable number of them had higher rates of prevalence so that this sample size proved feasible in generating good estimates for the majority of situations.

In the case of fluorosis, a health problem with a low prevalence, taking only the simple value (presence of fluorosis without considering levels of severity) will generate estimates with a high coefficient of variation; in other words, low precision. If levels of severity were included, precision would decrease still further, especially when considering the prevalence of severe and very severe stages. In general, therefore, the power to establish differences between the study domains, with this sample size, is fairly limited.

This also occurs due to the fact that the confidence intervals are affected by design effect when the estimate is obtained based on a complex sample design. As can be seen in the formula (1), the standard error is calculated including the square of the design effect (d). In the SBBrasil 2010, the design effect was estimated to be 2.0; however, depending on how the field research was carried out, this value was above that predicted in various state capitals. Allied to this, in some state capitals, the sample size of 250 was not reached, increasing the interval yet further and worsening the estimate. Thus, the formula shows that a combination of low prevalence, small sample size and high design effect produces high standard errors and, consequently, poor accuracy. For example, in the municipality of João Pessoa, with a sample of 139 children, there was an 8% prevalence with an interval of 2.4% to 23.8%, in other words, information which is next to useless.

Thus, the sample size for this health problem, estimated at 1,500 12-year-olds, leads to a discussion regarding the viability and feasibility of carrying out population studies for this health problem. A sample of 1,500 12-year-old children to be visited in their homes, if the same protocol was used as in the SBBrasil 2010, would call for approximately 19 thousand households to be visited (estimating a 2% proportion of the population of 12-year-old children and a mean of four individuals per household). Visiting 19 thousand households means including more than 60 census tracts and carrying out research in all of the residences, without sampling fractions.

Obtaining estimates with poor precision, as well as invalidating the comparative analyses (as exemplified in the case of the state capitals), also makes it impossible to carry out other studies which aim to identify associated factors based on ecological type designs, as the points estimate is imprecise.

Another possibility would be to compare data from previous years, such as 2003, in which the study was carried out based on the same criteria. However, there is the inherent problem of inconsistency in the data; although the data are considered reliable from the point of view of the validity of the index, it would be impossible to make a comparison as different models of analysis were used in the two surveys. The confidence intervals were calculated in different ways, in 2003 as if it were a simple causal sample and in 2010 considering weighting and cluster effects. This means that the 2003 intervals are artificially lower (proportionally) than those of 2010, as, in this case, the intervals were corrected by weighting “lengthening” the values. Thus, in practice, it is not possible to compare the results for the intervals, nor to carry out statistical tests.

To conclude, it is not possible to analyze trends in dental fluorosis in Brazil using the data available from the 2003 and 2010 studies, and these data are merely exploratory indicators of the prevalence of fluorosis. In general, the analysis conducted in this article indicates that discussion is needed concerning the technical and economic viability of investigating dental fluorosis in population based surveys for the country as a whole. This type of research should be carried out using local epidemiological studies with appropriate sampling plans.

Thus, it should be emphasized that this article does not aim to discourage epidemiological studies into dental fluorosis, nor to invalidate the data produced by the SBBrasil 2003 and SBBrasil 2010. The data have been essential in reinforcing the need for such studies to have specific and directed sampling plans in order to serve as basic guidance to strategies for controlling fluoridation of tap water, as well as monitoring the occurrence of episodes of endemic fluorosis.

References

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