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Black stains and dental caries in Brazilian schoolchildren: a cross-sectional study

Abstract

The aim of this study was to assess the prevalence of black stains (BS) and factors associated with their occurrence and to investigate the association of BS with caries experience after adjusting for other risk indicators. A school-based, cross-sectional study using multistage sampling of children aged 10–12 years from 20 private and public schools in Pelotas/Southern Brazil was conducted (n = 706). Children were evaluated for BS and dental caries (DMFT/dmft index) and socioeconomic information was collected by questionnaire. Univariate and multivariate Poisson regressions were used to assess variables associated with the prevalence of BS and with caries experience. The prevalence of BS was 5.81%. The mean DMFT/dmft was 1.54 (±1.91), with a maximum value of 10. Among the children with BS, mean dmft/DMFT was 1.22 (SD 1.68), with a maximum value of 6. After adjustments for demographics and socioeconomic variables, dental plaque and tooth brushing habits, prevalence of BS was associated with lower caries experience (RR 0.67; 95%CI 0.49–0.92). In conclusion, the presence of BS showed an association with lower dental caries experience in the evaluated population. Future studies should investigate the mechanisms behind this association.

Epidemiology; Oral Health, Dental Caries; Cross-Sectional Studies; Child

Introduction

A marked decrease in the prevalence of dental caries has been reported worldwide11. Marthaler TM. Changes in dental caries 1953-2003. Caries Res. 2004;38(3):173-81. doi:10.1159/000077752
https://doi.org/10.1159/000077752...
,22. Marcenes W, Kassebaum NJ, Bernabé E, Flaxman A, Naghavi M, Lopez A et al. Global burden of oral conditions in 1990-2010: a systematic analysis. J Dent Res. 2013;92(7):592-7. doi:10.1177/0022034513490168
https://doi.org/10.1177/0022034513490168...
, but it continues to be a major oral health problem. According to recent data, dental caries especially affects individuals in underdeveloped and developing countries, with higher prevalence in deprived populations22. Marcenes W, Kassebaum NJ, Bernabé E, Flaxman A, Naghavi M, Lopez A et al. Global burden of oral conditions in 1990-2010: a systematic analysis. J Dent Res. 2013;92(7):592-7. doi:10.1177/0022034513490168
https://doi.org/10.1177/0022034513490168...
.

Despite the significant improvement in oral health indicators in Brazil over the last few decades, dental caries is still a significant public health problem33. Antunes JL, Peres MA, de Campos Mello TR, Waldman EA. Multilevel assessment of determinants of dental caries experience in Brazil. Community Dent Oral Epidemiol. 2006;34(2):146-52. doi:10.1111/j.1600-0528.2006.00274.x
https://doi.org/10.1111/j.1600-0528.2006...
. Recent data from a National Survey (SB 2010) demonstrated that at 12 years of age, the mean decayed, missing and filled teeth (DMFT) was 2.1 and 56% of the children presented dental caries44. Roncalli AG. National oral health survey in 2010 shows a major decrease in dental caries in Brazil. Cad Saúde Pública. 2011;27(1):4-5. doi:10.1590/S0102-311X2011000100001
https://doi.org/10.1590/S0102-311X201100...
. Another important aspect in relation to the prevalence of dental caries in Brazil is the polarization of the disease, with 60% of the carious teeth found in only 20% of the 12-year-old school children55. Narvai PC, Frazão P, Roncalli AG, Antunes JL. [Dental caries in Brazil: decline, polarization, inequality and social exclusion]. Rev Panam Salud Publica. 2006;19(6):385-93. Portuguese. doi:10.1590/S1020-49892006000600004
https://doi.org/10.1590/S1020-4989200600...
. The multifactorial character of caries etiology (behavioral, environmental, biological and socioeconomic) is well-established in the literature, with the socioeconomic aspect playing a pivotal role in caries prevalence66. Peres KG, Peres MA, Araujo CL, Menezes AM, Hallal PC. Social and dental status along the life course and oral health impacts in adolescents: a population-based birth cohort. Health Qual Life Outcomes. 2009;7(1):95. doi:10.1186/1477-7525-7-95
https://doi.org/10.1186/1477-7525-7-95...
. Children from low-income families77. Piovesan C, Mendes FM, Ferreira FV, Guedes RS, Ardenghi TM. Socioeconomic inequalities in the distribution of dental caries in Brazilian preschool children. J Public Health Dent. 2010;70(4):319-26. doi:10.1111/j.1752-7325.2010.00191.x
https://doi.org/10.1111/j.1752-7325.2010...
, from parents with low schooling, with lower access to dental care and fluoride sources have an increased risk of presenting with the disease88. Antunes JL, Narvai PC, Nugent ZJ. Measuring inequalities in the distribution of dental caries. Community Dent Oral Epidemiol. 2004;32(1):41-8. doi:10.1111/j.1600-0528.2004.00125.x
https://doi.org/10.1111/j.1600-0528.2004...
.

Some studies have shown that the presence of black stains (BS) could be associated with a lower prevalence of dental caries in children99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
,1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.,1111. Gasparetto A, Conrado CA, Maciel SM, Miyamoto EY, Chicarelli M, Zanata RL et al. Prevalence of black tooth stains and dental caries in Brazilian schoolchildren. Braz Dent J. 2003;14(3):157-61. doi:10.1590/S0103-64402003000300003
https://doi.org/10.1590/S0103-6440200300...
,1212. Chen X, Zhan JY, Lu HX, Ye W, Zhang W, Yang WJ et al. Factors associated with black tooth stain in Chinese preschool children. Clin Oral Investig. 2014;18(9):2059-66. doi:10.1007/s00784-013-1184-z
https://doi.org/10.1007/s00784-013-1184-...
, possibly due to differences in microbial composition in individuals with BS1313. Heinrich-Weltzien R, Bartsch B, Eick S. Dental caries and microbiota in children with black stain and non-discoloured dental plaque. Caries Res. 2014;48(2):118-25. doi:10.1159/000353469
https://doi.org/10.1159/000353469...
. A population study in a birth cohort showed that when the researchers controlled for potential confounding and mediator factors, the presence of BS could have a protective effect for the occurrence of dental caries in primary dentition (age 5)1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
. In contrast, other studies have not revealed such protective effects1515. Panagidis D, Schulte AG. Caries prevalence in 12-year-old Cypriot children. Community Dent Health. 2012;29(4):297-301.,1616. Garcia Martin JM, Gonzalez Garcia M, Seoane Leston J, Llorente Pendas S, Diaz Martin JJ, Garcia-Pola MJ. Prevalence of black stain and associated risk factors in preschool Spanish children. Pediatr Int. 2013;55(3):355-9. doi:10.1111/ped.12066
https://doi.org/10.1111/ped.12066...
. It is important to point out that these studies have not controlled for potential risk indicators that could be associated with either black stains or dental caries.

The stains are present as dots or small areas of dark coloration that can also form a line that follows the contour of the marginal gingiva. The stains may also appear in a diffuse form, covering the tooth crown. Retentive tooth areas, such as grooves, pits, and fissures can be impregnated with this type of pigmentation, being difficult to be removed in these areas1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5..

There is a lack of population-based studies evaluating the prevalence of BS, but data from non-population-based investigations show a prevalence rate varying from 2.5% to 19%, depending on the region where the study was conducted, the population surveyed, or the individuals’ dietary habits99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
,1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.,1717. Ronay V, Attin T. Black stain: a review. Oral Health Prev Dent. 2011;9(1):37-45. doi:10.3290/j.ohpd.a21283
https://doi.org/10.3290/j.ohpd.a21283...
. Until now, nostudy has investigated if BS could also have a protective effect in older children, in mixed or permanent dentition, when controlling the analysis for confounders. Therefore, the aim of this study was to investigate the prevalence of BS and factors associated with its occurrence and to assess the association of BS with caries experience, after adjusting for demographic, socioeconomic and behavioral characteristics. We tested the hypothesis that BS is associated with lower levels of dental caries after adjusting for potential confounding variables.

Methodology

Design and sampling procedures

This cross-sectional study was part of a school-based epidemiological study, which investigated different general health outcomes (obesity, physical activity) and oral health outcomes (caries, gingivitis, malocclusion, erosion, enamel defects and the prevalence of black stains), in the city of Pelotas, in 20101818. Goettems ML, Correa MB, Vargas-Ferreira F, Torriani DD, Marques M, Domingues MR et al. Methods and logistics of a multidisciplinary survey of schoolchildren from Pelotas, in the Southern Region of Brazil. Cad Saúde Pública. 2013;29(5):867-78. doi:10.1590/S0102-311X2013000500005
https://doi.org/10.1590/S0102-311X201300...
. The study was approved by the Human Research Ethics of Federal University of Pelotas, and by the Education Department.

A two-stage sampling technique was used for subject recruitment. In the first stage, the primary units (schools) were randomly selected, considering the number of children enrolled in each school and the proportionality of public and private schools existing in the municipality. A total of 15 public and five private schools were selected. In the second stage selection in each school, three 4th to 6th grade classes were randomly selected and all children enrolled in these classes were initially eligible for the study and were invited to participate. Parents received a letter through their children explaining study aims and confidentiality and requesting parental consent for their child’s participation. The study excluded children with physical and/or mental disabilities.

The survey was carried out in children aged 8–12 years old (n = 1,211), but for the potential preventive effect of black stains on dental caries in permanent dentition, children aged 10–12 were selected, because there is a higher prevalence of caries in older kids and they have a higher number of permanent teeth. The sample size required for this study, considering a prevalence of dental black stains of 6%1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5., acceptable error of three percentage points, confidence level of 95%, an increase of 20% for losses and refusals and the sampling design effect estimated at 2.0, was 579 children. The minimum sample size of this study was large, because it also assessed other outcomes. The calculations were made with Epi Info 6.0 (Centers for Disease Control and Prevention, Atlanta, GA, USA).

Data collection

Data was collected using the parents’ questionnaire responses, interviews, and oral clinical examinations with the children. The research team visited schools a number of times between September and November 2010 in order to ensure a sample abstention of less than 10%.

A pre-tested questionnaire was sent to the parents through the children and included socio-economics questions (maternal schooling and familial income). The interview conducted with the children contained demographic information (sex and age) and questions about oral hygiene habits.

The oral clinical examination included assessment of dental plaque, BS and dental caries in this order. After the dental plaque evaluation, teeth were cleaned with dental gauze. Examination was performed in school chairs using individual artificial lights, dental mirrors and CPI probes1919. World Health Organization. Oral health surveys: basic methods. 4th ed. Geneva: World Health Organization; 1997.. The criteria to assess BS presence was based on the study of Koch et al.1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5., this criteria were also used in another study of our group1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
. Presence of black stains on teeth was defined as firmly adherent black dots, forming liner discoloration parallel to the gingival margin and/or covering up to one third or more of the clinical crown and the BS presence or absence was registered accordingly. At least two neighboring teeth, primary and/or permanent, should have been affected to consider the presence of black stains.

For the visible plaque index2020. Ainamo J, Bay I. Problems and proposals for recording gingivitis and plaque. Int Dent J. 1975;25(4):229-35., the first molars, central and lateral incisors of diagonal quadrants were examined, totalizing 6 teeth evaluated. Four sites in each tooth (mesiobuccal, midbuccal, distobuccal, and lingual) were assessed. The diagonal quadrants selected for examination were randomly chosen for each selected school2020. Ainamo J, Bay I. Problems and proposals for recording gingivitis and plaque. Int Dent J. 1975;25(4):229-35.. Dental caries in primary and permanent teeth was assessed using the dmft/DMFT index1919. World Health Organization. Oral health surveys: basic methods. 4th ed. Geneva: World Health Organization; 1997.. To assess dental caries experience in both dentitions, DMFT and dmft were added into one variable.

Both interviewers and examiners received prior theoretical and practical training. All the 6 examiners were Master or PhD students from Graduate Programs in Dentistry. The calibration process for dental black stains diagnosis was performed in lux. The in lux process consists of the projection of images showing different possible variations in the condition, thus testing the examiners in all examination possibilities when the condition assessed had low prevalence or large variability1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
. The process consisted of the projection of 24 images showing different clinical situations. The calibration exercise for dental caries consisted of the examination of 20 children with similar age of the sample. Kappa statistics were used to measure inter-examiner agreement, comparing with a gold-standard examiner. The mean kappa value was 0.70 (range 0.64–1.00) for dental black stains and 0.74 (range 0.62–0.79) for dental caries. Visible dental plaque index (VPI) was included in the training, but no analysis of agreement was performed due to the difficulties involved in maintaining the condition unaltered during the series of examinations.

Data analysis

Data were entered in duplicate and independently using EpiData version 3.1 [EpiData Association, Odense, Denmark] and analyzed using Stata 12.0 [Stata Corporation, College Station, TX, USA]. Descriptive analyses were initially performed.

The presence of BS was used as an outcome and as an independent variable. When BS was used as an outcome, dental caries was used as an independent variable; when dental caries was the outcome, BS presence was used as the independent variable.

First, we assessed BS as the dependent variable. To test the association of the studied variables and prevalence of black stains, Chi-square and Fisher’s Exact tests were used and Multivariate Poisson regression analysis was conducted, obtaining the prevalence ratios (PR) and their 95% confidence interval (95%CI). In this analysis, dental caries was used as an independent variable and it was dichotomized as absent (dmft/DMFT = 0) or present (dmft/DMFT ≥ 1).

Next, dental caries was assessed as a dependent variable (outcome) and the mean of dmft/DMFT was used. In this analysis, BS was used as an independent variable and it was dichotomized as absent and present (at least two neighboring teeth, primary and/or permanent, affected). Data were tested for homogeneity of variance (Bartlett’s test) and one-way ANOVA was used in bivariate analysis. Bonferroni comparison was used to compare the groups when the independent variable was found to be a significant factor affecting the caries experience. Multivariate models were also performed to assess the association between BS and dental caries experience, adjusting for potential confounders (n = 706 children). Rate ratios (RR) and their 95% CI were obtained for dental caries experience.

In both analyses, the visible plaque index was used as an independent variable. For the statistical analysis, the total sites presenting dental plaque were categorized in tertiles.

Results

A total of 1,744 children were eligible for the oral health survey (aged 8–12 years), of which 418 (24%) did not present the informed consent form signed by parents. Of those children with parental consent to participate in the study, 105 (7.9%) were lost because they were absent from school during data collection. The final response rate was therefore 69.4%, yielding a total sample of 1,211 children. In the present study, 706 children aged 10–12 years were included. The prevalence of dental BS was observed in 41 (5.81%) schoolchildren (Table 1). A higher prevalence was seen in children from public schools (6.80%) and in children who reported brushing their teeth only once a day (13.56%). In the bivariate analysis, there was no significant difference among BS and dental caries (p = 0.381). In the Poisson regression analysis (Table 2), after adjustments, a protective effect was present in occurrence of pigmentation with a higher brushing frequency. Children who reported brushing their teeth twice a day had 82% of protection and children who reported three times or more a day had 62% of protection.

Table 1
Association between independent variables and dental black stain in schoolchildren between 10 and 12 years old. Bivariate analysis. Pelotas, 2010 (n = 706).
Table 2
Association of dental black stains and independent variables in schoolchildren between 10–12 years old. Poisson regression analysis. Pelotas, 2010 (n = 706).

Regarding dental caries, the mean dmft/DMFT was 1.54 (standard deviation 1.91), with a maximum value of 10. Among the children with black stains, mean dmft/DMFT was 1.22 (SD 1.68), with a maximum value of 6. Mean dental caries experience was higher in younger children, those with mixed dentition, those with low maternal schooling and family income, and in those children from public schools. Children with higher plaque index presented higher DMFT/dmft values. The impaired perception about oral health was associated with caries experience (Table 3).

Table 3
Association between dental caries experience (DMFT/dmft) and dental black stain in schoolchildren 10–12 years. Bivariate and Poisson regression analysis. Pelotas, 2010 (n = 706).

Table 3 shows the results of the association between black stains and dental caries experience. After adjustments for sex, age, family income, mothers’ educational level, type of school, frequency of tooth brushing and VPI, the prevalence of black stains was associated with a lower DMFT/dmft (RR 0.67; 95%CI 0.49–0.92).

Discussion

The overall result of the present study was that children with black stains had a lower dental caries experience, when evaluating children aged 10 to 12 years after controlling for potential risk indicators. This finding corroborates the findings of a previous population-based study wherein black stains were associated with lower dental caries occurrence in primary dentition, when adjusting for social, demographic and behavioral factors1212. Chen X, Zhan JY, Lu HX, Ye W, Zhang W, Yang WJ et al. Factors associated with black tooth stain in Chinese preschool children. Clin Oral Investig. 2014;18(9):2059-66. doi:10.1007/s00784-013-1184-z
https://doi.org/10.1007/s00784-013-1184-...
,1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
. Other non-populational studies found this association in permanent dentition99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
,1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.. In contrast, a few other studies failed to detect such association1111. Gasparetto A, Conrado CA, Maciel SM, Miyamoto EY, Chicarelli M, Zanata RL et al. Prevalence of black tooth stains and dental caries in Brazilian schoolchildren. Braz Dent J. 2003;14(3):157-61. doi:10.1590/S0103-64402003000300003
https://doi.org/10.1590/S0103-6440200300...
,1515. Panagidis D, Schulte AG. Caries prevalence in 12-year-old Cypriot children. Community Dent Health. 2012;29(4):297-301..

A literature review showed that in most studies, a lower prevalence of caries was present in children with black stains1717. Ronay V, Attin T. Black stain: a review. Oral Health Prev Dent. 2011;9(1):37-45. doi:10.3290/j.ohpd.a21283
https://doi.org/10.3290/j.ohpd.a21283...
. However, differences were not statistically significant in all of the studies, and this absence of difference can be related to the use of univariate analysis methods. In addition, most of the studies investigating this potential association had not controlled for confounding factors. In addition, considering the low prevalence of black stains in most populations, there is a need to investigate this hypothesis in large samples to confer adequate power to the study. Even though our study was a school-based survey, it can also be considered a population survey in this age, since, according to local authorities, the presence of children in the evaluated age groups in the schools is nearly 100%. Moreover, our study has a large sample size that confers enough power to the study to detect the potential association.

The reasons behind the protective effect of black stains in relation to dental caries occurrence are still unclear. It has been speculated that bacteria that cause dark pigmentation have a low pathogenicity, and these bacteria compete with the cariogenic microbiota for the location sites, reducing the potential adhesion of these cariogenic bacteria and, as a consequence, decreasing caries development1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.. A recent study suggests that the microbial composition of the plaque might be associated with the protective effect of BS. They demonstrated an equal total number of bacterial counts in BS and non-discolored plaque samples. Therefore, significant differences in individual species of bacteria were detected with a significantly higher number of A. naeslundii and a significantly lower number of Lactobacillus sp. in the BS samples. The number of S. mutans tended to be lower in BS samples than in nondiscolored plaque samples and the numbers of S. sobrinus were not considerably different between the two1313. Heinrich-Weltzien R, Bartsch B, Eick S. Dental caries and microbiota in children with black stain and non-discoloured dental plaque. Caries Res. 2014;48(2):118-25. doi:10.1159/000353469
https://doi.org/10.1159/000353469...
.

Another hypothesis is related to a probable higher content of total calcium and inorganic phosphates in the group of children with black spots2121. Surdacka A. [Chemical composition of the saliva in children and adolescents with black tartar]. Czas Stomatol. 1989;42(10-12):525-33. Polish., which could reduce the caries occurrence by reducing the dissolution of enamel, allowing the maintenance of a more stable pH, and providing higher buffer capacity of saliva2222. Garan A, Akyüz S, Oztürk LK, Yarat A. Salivary parameters and caries indices in children with black tooth stains. J Clin Pediatr Dent. 2012;36(3):285-8. doi:10.17796/jcpd.36.3.21466m672t723713
https://doi.org/10.17796/jcpd.36.3.21466...
. The regular consumption of iron-rich foods or iron supplements during early childhood could be reasons for favoring chromogenic microbiota development1616. Garcia Martin JM, Gonzalez Garcia M, Seoane Leston J, Llorente Pendas S, Diaz Martin JJ, Garcia-Pola MJ. Prevalence of black stain and associated risk factors in preschool Spanish children. Pediatr Int. 2013;55(3):355-9. doi:10.1111/ped.12066
https://doi.org/10.1111/ped.12066...
. Lactoferrin, a major iron-binding protein constituent of milk and cheese, has antibacterial activity against S. mutans, preventing dental caries development2323. Mesonjesi I. Are extrinsic black stains of teeth iron-saturated bovine lactoferrin and a sign of iron deficient anemia or iron overload? Med Hypotheses. 2012;79(2):219-21. doi:10.1016/j.mehy.2012.04.044
https://doi.org/10.1016/j.mehy.2012.04.0...
. However, a recent study has concluded that metallic ions do not seem to be the origin of BS2424. Parnas L, Chevion M, Berenshtein E, Faibis S, Moskovitz M. Are there metallic traces in black extrinsic dental stain? Quintessence Int. 2013;44(5):427-32. doi:10.3290/j.qi.a29149
https://doi.org/10.3290/j.qi.a29149...
.

In this sample, the prevalence of dental black stains was 5.8%. In Brazil, the prevalence figures ranged from 3.5% at 5 years1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
to 14.8%1111. Gasparetto A, Conrado CA, Maciel SM, Miyamoto EY, Chicarelli M, Zanata RL et al. Prevalence of black tooth stains and dental caries in Brazilian schoolchildren. Braz Dent J. 2003;14(3):157-61. doi:10.1590/S0103-64402003000300003
https://doi.org/10.1590/S0103-6440200300...
in a population aged 6–12 years. Similar results were found in studies in other countries. In Italy, a prevalence of 6.0% was found among children aged 6 to 12 years1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5., and in Spain, a prevalence of 7.5% was detected in children aged 4 to 11 years2525. Paredes Gallardo V, Paredes Cencillo C. [Black stain: a common problem in pediatrics]. An Pediatr (Barc). 2005;62(3):258-60. Spanish. doi:10.1157/13071841
https://doi.org/10.1157/13071841...
. The only population-based study investigating black stains in primary dentition, in the same city that our investigation took place, has also found a low prevalence (3.6%). This variation between studies can be attributed to differences in sample selection when the evaluation is performed at public schools1111. Gasparetto A, Conrado CA, Maciel SM, Miyamoto EY, Chicarelli M, Zanata RL et al. Prevalence of black tooth stains and dental caries in Brazilian schoolchildren. Braz Dent J. 2003;14(3):157-61. doi:10.1590/S0103-64402003000300003
https://doi.org/10.1590/S0103-6440200300...
or rural schools99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
or as this study that evaluates public and private school population1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.. Additionally, there may be differences in data collection since information about the training and calibration of examiners is not explained in detail.

The factors associated with the occurrence of black stains were also assessed. When dental plaque was not associated with the outcome, tooth-brushing frequency was the only factor influencing in BS prevalence. Due to the design limitations, it is not possible to confirm if there is a causal relationship between a higher tooth brushing frequency and a lower prevalence of black stains, although it is possible that the presence of stains might influence oral hygiene habits. Morphological studies reported that BS are a special type of dental plaque2626. Theilade J, Slots J, Fejerskov O. The ultrastructure of black stain on human primary teeth. Scand J Dent Res. 1973;81(7):528-32.. Thus, it has also been assumed that the black stains reveal plaque at the tooth surface, resulting in different oral hygiene habits and/or demand for dental care1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5..

Other possible factors have been pointed out in the literature, but none have been confirmed in this study. França-Pinto el al.1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
detected a higher frequency of black stains in children from lower socioeconomic backgrounds, and Chen et al.1212. Chen X, Zhan JY, Lu HX, Ye W, Zhang W, Yang WJ et al. Factors associated with black tooth stain in Chinese preschool children. Clin Oral Investig. 2014;18(9):2059-66. doi:10.1007/s00784-013-1184-z
https://doi.org/10.1007/s00784-013-1184-...
found the association with birthplace, parents’ educational level, intake frequency of soy sauce and use of nursing bottle. The effect of dietary habits was pointed out as a possible cause of black stains, with children with traditional dietary habits (sustainable community structures, limited exchange of goods and food, and limited exposure to a Western lifestyle) being more susceptible to BS99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
. If BS is associated with biofilms composition, the fact that children with BS are exposed to lower cariogenic diet might also be connected with a lower caries occurrence, regardless of the presence of BS.

It is worth mentioning that black stains and dental caries share common co-variables such as socioeconomic and behavioral characteristics1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
. This fact can lead to a positive confusion, i.e. an association that was not significant in crude analysis, became statistically associated after adjustments for these co-variables, reinforcing the need to use a statistical approach with multivariable analysis to assess the possible relationship between black stains and dental caries1414. França-Pinto CC, Cenci MS, Correa MB, Romano AR, Peres MA, Peres KG et al. Association between black stains and dental caries in primary teeth: findings from a Brazilian population-based birth cohort. Caries Res. 2012;46(2):170-6. doi:10.1159/000337280
https://doi.org/10.1159/000337280...
.

As mentioned above, one of the strengths of this study is the representative sample, including children from private and public schools, providing different socioeconomic backgrounds. Furthermore, inter-reliability was satisfactory. The selected criteria used to detect BS was based on previous studies, allowing comparisons between the results99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
,1010. Koch MJ, Bove M, Schroff J, Perlea P, García-Godoy F, Staehle HJ et al. Black stain and dental caries in schoolchildren in Potenza, Italy. ASDC J Dent Child. 2001;68(5-6):353-5.. In addition, this study is only the second one to perform an investigation about the relationship between dental caries and black stains, using a statistical approach that controlled for potential confounders, and it is the first one to work this in permanent/mixed dentition. Besides considering several demographic, social and behavioral factors that may have influenced the presence of BS and its caries protective effect1313. Heinrich-Weltzien R, Bartsch B, Eick S. Dental caries and microbiota in children with black stain and non-discoloured dental plaque. Caries Res. 2014;48(2):118-25. doi:10.1159/000353469
https://doi.org/10.1159/000353469...
, our study also included a dental plaque evaluation in the multivariable analysis. One limitation is the fact that some of the variables possibly associated both with dental caries and black stains, such as dietary habits99. Heinrich-Weltzien R, Monse B, Palenstein Helderman W. Black stain and dental caries in Filipino schoolchildren. Community Dent Oral Epidemiol. 2009;37(2):182-7. doi:10.1111/j.1600-0528.2008.00458.x
https://doi.org/10.1111/j.1600-0528.2008...
could not be assessed due to methodological issues, since the study was part of a large multidisciplinary survey. However, the inclusion of variables associated with both conditions in the model could probably reveal a stronger association between BS and dental caries. Another limitation of this study was the cross-sectional design, which impairs the establishment of causality.

Conclusions

In conclusion, in this school-based sample the prevalence of black stains was associated with lower caries experience. It is recommended that further epidemiological studies adopting an appropriate design and statistical methods assess the factors possibly involved in the phenomenon of black stains and its relationship with dental caries.

Acknowledgments

The authors are grateful to the CNPq (National Council for Scientific and Technological Development) for the research funding grant #402350 for the PI (F.F.D.), PEC-PG scholarship (TMLM) and PhD scholarship (M.L.G.). Moreover, the authors would like to thank Colgate for the oral hygiene kits distributed during fieldwork.

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Publication Dates

  • Publication in this collection
    2016

History

  • Received
    11 Sept 2015
  • Reviewed
    13 June 2016
  • Accepted
    25 July 2016
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