Introduction

Caries is a chronic multifactorial condition¹ that may appear as early as nine months of age². According to the World Health Organization (WHO), more than 530 million children worldwide suffer from caries in deciduous teeth³. The prevalence of caries in preschool children ranges between 24% and 63%^4,5. In Mexico, the prevalence of caries in children between the ages of nine months and 12 years varies from 35% to 98%⁶. At 2 years of age, 47% of children have caries in deciduous teeth and the proportion increases to 73% in the 4-year-old group⁷. In 2015, in the south and southeastern areas of the country, which includes the state of Guerrero, the prevalence of caries in children aged 3 to 5 years was 62%⁸. In Mexico, the DMF index (decayed, missing, and filled teeth)⁹ in preschool children had values from 1.0 to 7.2¹⁰, and the OHI-S DI-S¹¹ was estimated to be adequate in 65% of preschoolers, regular in 31%, and deficient in 3%¹².

The factors associated with a higher prevalence of caries are consumption of foods with a high sugar content^13,14, older age of the child^15,16, low educational level of the parents^17,18, and prolonged breastfeeding for more than 24 months¹⁹, although the latter is controversial²⁰. Other factors that have also been reported to be associated with caries are the presence of dental biofilm²¹, consumption of sugary drinks²², frequency of toothbrushing during the day²³, toothbrushing without parental supervision¹⁷, and low socioeconomic level of the family¹⁸. The factors associated with dental biofilm in preschoolers have been poorly studied; it has been found that older infants, the number of infants in the family, and the low educational level of the mother are associated with dental biofilm ²⁴.

There are few studies on caries and OHI-S DI-S index in the child population of Acapulco and the state of Guerrero. The present study aimed to estimate the prevalence of caries and oral hygiene and associated factors, such as family sociodemographics and dietary and hygienic habits in preschoolers in Acapulco, Guerrero, Mexico.

Material and methods

This cross-sectional study was conducted between September and November 2019 in five public preschools in Acapulco, Guerrero, Mexico. The study universe consisted of preschoolers aged 3 to 5 years enrolled in the participating schools. The selection of the preschools was by convenience. With the total size of the preschool population (n=383) we estimated the effect to be detected, using the following data: 50% proportion with caries in the unexposed group; significance level of 95%; and study power of 80%; resulting in a minimum odds ratio to be detected of 1.9.

The study area was the upper area of Acapulco, in the center of the city, characterized by a population of low-to-medium socioeconomic level. The units of observation or analysis were the children and the children’s parents. The inclusion criteria were preschool children enrolled in the selected school, attending on the day of the study, whose parents agreed to their participation and allowed the oral examination. Exclusion criteria were children with disabilities or the presence of any condition that prevented clinical examination of the oral cavity. The elimination criteria were that the parent or guardian did not complete the questionnaire or an incomplete or illegible clinical examination record.

The research protocol was reviewed and approved by the ethics committee (Folio Number 2019-009) of the Centro de Investigación de Enfermedades Tropicales (CIET) of the Universidad Autónoma de Guerrero (UAGro). The educational authorities of the five schools gave their authorization. Parents or guardians gave their authorization for the preschoolers to participate in the study through a signed informed consent letter. In addition, each preschooler, who had parental or guardian authorization, was asked for verbal permission to participate in the study. The information provided was confidential but not anonymous and used exclusively for academic and research purposes. At the end of the oral examination, each preschooler received fluoride, toothpaste, and toothbrush, and the brushing technique was reaffirmed.

The measurement instruments consisted of a questionnaire for the parents or guardians of the preschoolers and a format with the odontogram of international use to measure the DMF-d9 index, the Simplified Oral Hygiene Index, and the Simplified Oral Hygiene and Disposal Index (OHI-S DI-S)¹¹.

The questionnaire, with 21 questions validated in other studies, obtained information from parents and preschoolers^21,23. From the households, information was obtained on the number of members, the number of people living in the home, and the availability of drinking water. The following variables were measured for parents: age, marital status, occupation, schooling, monthly income, perception of their child’s current nutritional health, and knowledge of caries and degrees of caries. The following variables were measured for preschool children: age and sex; age at ablactation; frequency of consumption of sweets and sugar-sweetened beverages; age at the beginning of toothbrushing; frequency of toothbrushing and whether it was before or after a meal; and adult supervision of toothbrushing.

The consumption of sweets was estimated by the following question: During the day, how many times does the child consume candies? The response codes were the number of times reported by the parents or guardians. The measurement of the frequency of consumption of sugar-sweetened beverages was made with the question: How often does the child drink sugar-sweetened beverages? The response codes were none or no consumption, infrequent, frequent, and very frequent.

The clinical examination of the oral cavity of the preschoolers was performed by 20 examiners, 10 operators, and 10 assistants from the Faculty of Dentistry of the Autonomous University of Guerrero. The examiners were trained in the diagnosis of common oral cavity pathologies and in the observation and clinical examination of teeth. Only examiners who had a Kappa test greater than 85% in the diagnostic concordance of the examination of the teeth were selected.

The odontogram recorded the presence of caries in the children through the DMF-d index, which was calculated by adding the decayed, missing, and filled primary teeth⁹. The DMF-d index was classified as very low from 0 to 1.1; low, from 1.2 to 2.6; moderate, from 2.7 to 4.4; and high, from 4.5 to 6.5¹⁰. To estimate the OHI-S DI-S, teeth numbers 55, 51, 65, 85, 71, and 75 were checked, it was calculated with the codes, 0 no presence of debris or stains; 1, presence of soft debris covering less than one-third of the tooth surface or there is the presence of extrinsic pigmentation without other debris, regardless of the surface covered; 2, presence of soft debris covering more than one third but less than two-thirds of the exposed tooth surface; and 3, presence of soft debris covering more than two-thirds of the exposed tooth surface¹¹.

Two outcome variables (dependent variables) were measured, caries and the presence of dental biofilm. The operational definition of caries was the presence of a dark cavity evident in any of the teeth examined in the oral examination of the preschooler. The operational definition of preschooler with dental biofilm was when the OHI-S DI-S score in the oral examination was 1.5 to 3.0.

For the analysis of associated factors, the outcome variables were dichotomized as follows: presence or absence of caries; and presence of dental biofilm if the OHI-S DI-S score was 1.5 to 3.0 and absence of biofilm if the score was 0 to 1.4. Potentially associated variables were classified as present or absent exposure factors in the case of nominal variables, and in the case of ordinal, discrete, and continuous variables, different levels of exposure were explored until the greatest contrast was determined.

The information collected was digitized using EpiData software²⁵ and the statistical analysis was performed with CIETmap²⁶. Simple frequencies of the relevant variables were obtained. Bivariate and multivariate analysis was performed with the Mantel-Haenszel procedure²⁷. The strength of association was estimated by odds ratio (OR) and cluster-adjusted 95% confidence intervals (CI95%acl) according to Lamothe’s proposal²⁸. The multivariate analysis began with the saturated model with all the significant variables in the bivariate analysis, eliminating each of the variables that did not maintain 95% significance, until the final model was reached. Effect modification was assessed with X2 squared heterogeneity (X2het), as proposed by Zelen²⁹.

Results

Of the 383 preschoolers enrolled, 51 (13%) did not attend school on the day of the study. Only three (0.78%) parents refused to allow their children to participate. Six preschoolers were excluded because they had a disability, and one participant was eliminated because his parent or guardian did not respond to the questionnaire. The analysis of the study was made on 322 preschoolers who had an oral check-up and there were an equal number of parents or guardians surveyed.

Discussion

The prevalence of caries was higher in girls than in boys. Also, the presence of dental biofilm was higher in girls. The DMF-d index was moderate. The factors associated with an independent effect on caries were the female sex and the high frequency of consumption of sugar-sweetened beverages. The factors that had an independent association with OHI-S DI-S were the female sex and the number of people over five in the dwelling. The purpose of the study was to generate information that would allow us to know the problem of caries and dental biofilm and to identify associated factors. The results of this research confirm the need to intensify some specific actions for caries prevention and dental plaque in the preschool population.

Developed countries have reported lower caries prevalence figures of 15% to 47%^15,18. This may reflect better access to health services, better educational level, and higher parental income¹⁸. Social development contributes to a good level of preschoolers’ health, mainly at the oral and dental levels. Some researchers in developing countries have reported caries prevalences between 60% and 70% in preschoolers close to the ones we report²¹. Other authors in Mexico have reported high percentages (90%) of infants with caries^5,12, although these studies were performed in infants, from zero to 12 years of age, users of a pediatric dentistry clinic. It is possible that the patients attended because of a dental problem and since it is a specialized service, there was a higher proportion of affected children¹⁰.

We found that the female sex factor was associated with caries. This is discordant with what is reported in world literature. Other studies have found that the male gender is the most affected^4,14. In one study, female sex was associated with caries in the permanent dentition³⁰. The reviewed literature did not offer a possible biological or physiological explanation between girls and boys of this age related to caries. It could be a social-cultural cause, since in general, the population of Acapulco has greater care and preferences for the male gender. Another study, also in Mexico, found the opposite³¹. Another author who similarly found a higher occurrence of caries in girls stated that it may be due to the earlier appearance of teeth and the access that girls may have to food preparation, since in some cultures cooking is closely linked to the female gender³². In one study, a higher prevalence of dental problems was found in girls, and the author reported that nuclear families act as a protective factor against caries³⁰.

In our study, frequent consumption of sugar-sweetened beverages was associated with caries; this association has also been reported in another study²². The cariogenic nature of sugars in the oral cavity has been demonstrated, particularly if there is no oral hygiene after consumption^13,14. The presence of caries at an early age possibly reflects the cultural habit of the population that introduces sugary drinks into the diet of preschoolers at an early age³³.

The average OHI-S DI-S was 1.4; another author reported an index of 1.2 in children of the same age²⁴, a figure close to our result. The study was in preschoolers with similar socioeconomic characteristics, and the small difference may be because it measured only male preschoolers.

In our study, the female gender was associated with a more deficient OHI-S DI-S; in other studies, this association has not been reported^24,34. In the data analysis of our research, we found that girls with single or cohabiting mothers had a higher percentage of poor OHI-S DI-S than daughters of mothers who reported being married; the size of the study sample prevented a more in-depth analysis. This marital status may indicate a greater need for work and consequently less money available for hygiene supplies and less time available for oral care of their girls. However, we found that parental supervision of toothbrushing was equal between girls and boys, while the frequency of brushing was lower in girls. The combination of proper oral hygiene techniques and high frequency of toothbrushing reduces dental biofilm rates³⁵.

The habitation of five or more people in the dwelling was associated with poor OHI-S DI-S in preschoolers. One study found this association with older age of schoolchildren, higher number of children in the dwelling, and lower schooling of mothers²⁴. The association may be due to the economic constraints of the families; it is common that the greater the number of family members, the worse the oral health condition.

This study, due to its cross-sectional design, has limitations regarding the temporality of caries causation. It is reasonable to assume that caries occurred after exposure to the consumption of sugar-sweetened beverages. Another limitation was the missing data; 16% of preschoolers were absent; it is possible that their socioeconomic conditions are more precarious than those of the study participants. In this sense, the results could be overestimated. The results of the present study are representative of preschool units in the upper zone of the municipality of Acapulco; however, they could be generalized to other preschool units in other municipalities of the State of Guerrero or the country with similar characteristics.

Conclusion

The prevalence of caries was high, and the oral hygiene index was regular. The factors associated with caries were female sex and frequent consumption of sugar-sweetened beverages. The latter could be modified at a low cost through preventive programs implemented by health authorities. The factors gender of the preschooler and the number of people living in the home were the variables associated with the poor oral hygiene index. Although the latter factors are conditioning, they set a guideline for paying more attention to oral health in these population groups.