Epidemiological pattern of malocclusion in Brazilian preschoolers

This study aimed to evaluate the prevalence and distribution profile of malocclusion in Brazilian preschoolers and its association with macro-region, housing, gender, and self-reported race. In total, 6,855 children aged five years participating in the National Oral Health Survey (called SB Brasil 2010) were analyzed. Malocclusion was diagnosed according to the Foster and Hamilton index. We conducted descriptive, bivariate and multiple regression analyses (PR/CI95%). We identified that 63.2% of children had at least one of the occlusal problems evaluated: canines’ key (22.9%), overjet (32.9%), overbite (34.6%), and posterior crossbite (18.7%) and, thus, were considered with malocclusion. Higher probability of the presence of malocclusion was identified among the residents of the Midwest (1.08/95%CI 1.01-1.15), Northeast (1.21/95%CI 1.14-1.28), Southeast (1.27/95%CI 1.20-1.34) and South (1.34/95%CI 1.26-1.42) regions when compared to residents in the North. It was also higher among female children (1.06/95% CI 1.02-1.09). No associations were identified concerning race and location of the municipality (capital/no capital). A high prevalence of malocclusion was identified in Brazilian preschoolers, and it was associated with gender and the macro-region. These findings may contribute to expanded public policies and greater access to treatment for this population.


Introduction
The oral health conditions of Brazilian preschoolers are worrisome, since although there have been slight improvements in the last two epidemiological surveys carried out in the Brazilian population 1,2 , such as around 6% increase in caries-free 5-year-olds, this population segment is still affected by a history of untreated disease, responsible for more than 80% in the index composition, and has different dental treatment needs besides the presence of occlusal problems 2 .Dental care in the first years of life facilitates the identification of risk factors for oral diseases and problems, allowing the planning and implementation of preventive and curative procedures 3 , thus reducing the impact of these problems on the daily life of these individuals 4 .
The occlusion-related problems are characterized by alterations in the development of maxillaries, which can result in functional, aesthetic and psychosocial alterations in individuals 5,6 , and are the result of an interaction of genetic and environmental factors [7][8][9] .Among preschoolers, occlusion-related problems have been associated with different factors, such as anthropometric deficit 10 , unhealthy habits, such as pacifier or finger sucking habit 11 , dental eruption disorders 12 and other oral disorders, such as dental traumatism 13 and dental caries 14 .Also, the presence of malocclusion in this age group has been associated with a negative impact on the quality of life of children and their families 15 .These findings have derived from population-based studies, contributing to the understanding of this issue in preschoolers.
In general, there is a high prevalence of occlusal problems among preschoolers, varying in different countries, with rates close to 20% in Spain 16 and 70% in Lithuania 17 , as identified in previous population studies.In Brazil, the prevalence of occlusal problems in preschoolers has ranged from 28% to 80%, according to the location of the studies 11,13,15,18 , which highlights the possibility of the association of regional characteristics in the occurrence of this problem, because malocclusion evaluation criteria used are different in these studies.According to data from the last two national oral health surveys of the Brazilian population 1,2 , the presence of an occlusal problem in 5-year-olds increased by 28.2% between the two surveys 12 .
However, literature evidenced no studies that have characterized the epidemiological pattern of occlusal problems among preschoolers, consider-ing a representative sample of this population in Brazil.Besides, due to the different prevalence of this disease in the different Brazilian municipalities, pointed out by previous studies 11,13,15,18 , the association of malocclusion with the geographic region of residence of these individuals, as well as other associated factors, must be evaluated.In this line of reasoning, regional differences in the pattern of impairment may guide the planning of preventive and corrective actions geared to the problem.Therefore, this study aimed to characterize the pattern of malocclusion among Brazilian preschoolers and identify the factors associated with its presence, based on data from the National Oral Health Survey conducted in 2010 (SB Brazil).

Design and sampling
This is a cross-sectional, analytical study based on the database of the epidemiological survey of the Oral Health conditions of the Brazilian population carried out in 2010 2 .
The survey in question was conducted according to the criteria proposed by the WHO, in which a representative sample of the Brazilian population in the index age groups was interviewed and examined through clinical-epidemiological examinations performed by dentists under natural light in their households regarding oral health, demographic and socioeconomic conditions, use of dental services and subjective oral health issues.The sample consisted of residents from 177 Brazilian municipalities, from the five Brazilian macro-regions (North, Northeast, Midwest, Southeast, and South), including the 27 capitals, selected by multi-stage probabilistic sampling by conglomerates, with probability proportional to the size of the population and considering a design effect (deff) of 2.0.The examinations and interviews were performed by dental surgeons previously trained and calibrated by the consensus technique, with the minimum acceptable value of Kappa for each examiner, age group and injury being studied equal to 0.65 19 .
In this study, we considered a database selection of 5-year-olds who were examined for malocclusion (7,045) excluding those of yellow (138) or indigenous (52) ethnicity, due to low representativity 20 , totaling a sample of 6,855 5-yearold preschoolers.

Evaluation of malocclusion
Malocclusion was diagnosed by the Foster and Hamilton Index 21 , which consists of four measures: canines' key, overjet, overbite, and posterior crossbite.The measurement (in millimeters) was performed with teeth in occlusion and the probe parallel to the occlusal plane.The child with at least one of these abnormalities was characterized as "malocclusion", otherwise, as "normal occlusion".In this study, the presence of malocclusion was adopted as the dependent variable (outcome).

Independent variables
The independent variables considered were: macro-region (North, Midwest, Northeast, Southeast, South), geographic location (capital, inland), gender (male, female) and self-declared ethnicity (white, black/brown).Such information was retrieved from questionnaires applied to those responsible for preschoolers.

Statistical analysis and ethical considerations
Initially, the variables were described through their frequency distributions.Concerning the variables underlying the Foster and Hamilton Index, as well as for the outcome (malocclusion), 95% confidence interval was estimated for their respective prevalence.In the bivariate analysis, the Chi-square test was used to evaluate the existence of an association between the outcome and the independent variables.Variables with a detailed level (p-value) less than or equal to 0.20 were selected for the multiple model.The Poisson regression model, with robust variance, using the prevalence ratio (PR) as a measure of association was adopted in the multiple analysis.Statistical analyses were performed in the SPSS program 18.0.
The epidemiological survey was carried out respecting the ethical principles of National Health Council Resolution Nº 196/96 and was approved and registered by the National Research Ethics Commission (CONEP).

Results
A total of 6,855 five-year-old preschoolers were included in this study, most of which were males, residing in the Northeast and North regions of the country and of black or brown skin color (Table 1).
Regarding the evaluation of malocclusion, 4,332 (63.2%) preschoolers had at least one of the occlusal problems evaluated and, thus, were considered as having malocclusion.They were characterized for the presence of canines' key, overjet, overbite and posterior crossbite (Table 2).
The bivariate analysis showed that only Brazilian macro-region and gender remained associated with malocclusion (Table 3).Significant associations of the presence of malocclusion with the Brazilian macro-region (p = 0.000 to 0.026) and gender (p = 0.003) were identified (Table 4) in the Poisson multiple regression analysis.

Discussion
The understanding of the pattern of malocclusion in Brazilian preschoolers allows us to estimate the regional demand characteristic for orthodontic treatment, besides knowing the profile of these individuals.From the viewpoint of public health, the identification of sociodemographic differences values the need for decentralized public oral health policies, which facilitates the understanding that regional characteristics interfere with the prevalence and severity of oral diseases and issues.The prevalence of malocclusion among Brazilian preschoolers, associated with the Brazilian macro-regions and gender of preschoolers, was 63.2%, that is, these individu- als had at least one of the occlusal problems evaluated (canines' key, overjet, overbite or anterior crossbite).The characterization of malocclusion in 5 year-olds has not been well clarified in the literature, considering a representative sample of Brazil, hindering their comparison.Similar prevalence of malocclusion was found among children from Germany (72%) 12 and Lithuania (71%) 17 .A different prevalence is observed when considering studies performed in different regions of Brazil pointing to local characteristics of the disease.A prevalence similar to that recorded in this study was identified in a previous work conducted in Bauru (SP) 11 , with involvement in 50 and 60% among children aged 3 to 5 years, using different diagnostic criteria.A previous study carried out in another state (MG) identified a lower prevalence rate of 28.4%, using the Foster and Hamilton criteria for children aged 3-5 years 15 .On the other hand, a higher prevalence was identified in a municipality in the South region (Canoas, RS), with a rate of 69.9% 4 , considering different diagnostic criteria.Regional differences and the different diagnostic criteria used in the studies may explain the high variability in prevalence among the different Brazilian locations.Despite this, considering the adverse effect of this condition on the quality of life of preschoolers and their families 15 , as well as a possible presence of these conditions in the deciduous dentition will result in a greater need for orthodontic treatment in the permanent dentition 22 , the prevalence rate found is of concern.
Furthermore, we identified the association between the presence of malocclusion with the geographic region and gender of the preschoolers based on the adjusted analysis.Higher prevalence was identified among preschoolers residing in the Midwest, Northeast, Southeast and South regions, by increasing order of likelihood of affection when compared to the North region of the country.Similar differences among Brazilian regions in malocclusion were also identified in Brazilian 12-year-old students 23 and adolescents (15-19 years) 24 .Other oral diseases in preschoolers, such as dental caries, have also shown differences of involvement according to the geographic region of Brazil 25 .Considering the size of Brazil in territorial terms and the existence of regional and cultural differences, it may be that health behaviors are influenced by these differences and, consequently, impact health outcomes, such as malocclusion.The following stand out among these regional and cultural differences: the so-  cioeconomic level of families and municipalities, which may influence access to dental services; the educational level of the residents of the regions, which may influence behavior; behavioral differences due to cultural issues that may lead to the event of occlusal issues.
Behavioral differences between residents of different regions of Brazil can be exemplified by the country's use of health services 2,26 .Also, some behaviors have been indicated as risk factors for the event of occlusal problems 11 , and these may vary according to cultural differences, that is, different regions may lead to different behaviors that may affect the event of malocclusion.Also, the impairment profile of oral problems 2 , as well as access and health care process may show differences among Brazilian regions 27 , which may cause a higher occurrence of oral issues.Thus, health actions should consider such differences in order to adequately serve the population.
We also identified that malocclusion was higher among female preschoolers, which was also identified in a previous study conducted in a municipality in the Southeast region (Bauru -SP) 11 .The association between malocclusion and gender, with a higher probability among girls, was also identified among Brazilian adolescents 24 and Indigenous 28 .The opposite result was identified for Brazilian 12-year-old children, with a higher prevalence of male malocclusion 29 .As for the dif-ferences between Brazilian regions, sociodemographic issues are known to influence the event of oral health outcomes, such as malocclusion.It is noteworthy that, despite the identified association, in the field of health, the female gender has been considered a protective factor, with a lower occurrence of issues 23 .One possible explanation for the difference in the association with gender between the ages of 5 and 12 is the current period of life of these children.At five years of age, health conditions and behaviors are mostly modulated by actions of those responsible, i.e., they are a reflection of the care or importance of the person responsible for the child, since it is a very early age and there is no independence concerning health.Therefore, this higher occurrence in females does not necessarily represent a risk profile.By the age of 12, the health condition becomes more reflexive of the behaviors and personality of the child itself.Another factor to be considered is the value of the prevalence ratio identified for the female gender in this study (1.06), which is close to 1, showing that despite the difference between genders, the likelihood of occurrence of malocclusion is quite high, that is, girls are only 6% more likely to have the outcome compared to boys.
The characterization of the epidemiological pattern of involvement and possible factors associated with malocclusion among Brazilian preschoolers can support health actions and improvement in oral health public policies aimed at reducing this condition.Also, considering that preschoolers are a population segment that is more likely to accept new habits, at this stage, health education and education of their families, can be an effective alternative to affect oral health outcomes 30 positively.Thus, there is a need to create or streamline educational activities of a permanent nature 30 to reduce risk factors for malocclusion.
Occlusal problems can develop early, at early ages, and can hardly be self-corrected, which makes the deciduous teething phase an adequate period for the introduction of preventive measures or treatment.Furthermore, considering the negative impact of malocclusion on the child's quality of life, which may affect the family context, it is necessary to solve this problem as early as possible.Among the occlusal conditions evaluated, there was a significant class II affection of canines, increased overjet and posterior crossbite.Clinical studies have addressed different therapeutic modalities for the treatment of occlusal problems in preschoolers, as well as intervention measures to control possible risk factors 31,32 .An example of this is a study by Lippold et al. 32 , which indicated initial maxillary expansion followed by U-bow activator therapy for the treatment of posterior crossbite in children with deciduous or mixed dentition from a clinical study 32 .Furthermore, the use of psychological interventions and orthodontic appliances, such as the palatal arch, has been shown to be effective in the cessation of non-nutritive sucking habits that could lead to malocclusion among children, as shown by a systematic literature review 31 .
In this line, in Brazil, Dental Specialties Centers (CEOs) may include corrective orthodontic treatment in the list of specialties since 2011.However, removable orthopedic and orthodontic appliances can be performed both in primary care and at CEOs 33 , procedures which would be of great value for the early correction of malocclusions, thus contributing to the improvement of oral health of a significant proportion of Brazilian preschoolers.
This study does not allow establishing cause and effect relationships among the factors studied.Therefore, future studies, mainly of a longitudinal nature, may clarify the possible influence of the associated factors in the occurrence of occlusal problems in Brazilian preschoolers.Also, considering the relevant Brazilian social inequalities, it is necessary to evaluate the possible influence of socioeconomic aspects in the occurrence of this problem.Despite this, the results shown are valid and representative of the population of a significant sample of 5-year-old Brazilian preschoolers, allowing further clarification on the prevalence and sociodemographic factors associated with malocclusion.A high prevalence of malocclusion among the Brazilian preschoolers was identified from the data, and this prevalence was higher among females and varying by Brazilian macro-regions.

Table 1 .
Distribution of 5-year-old children by region, geographic location, gender, and skin color.Brazil, 2010.

Table 2 .
Condition of dental occlusion assessed by the Foster and Hamilton index at five years of age.Brazil, 2010.

Table 3 .
Distribution of dental occlusion by region location, gender and skin color in children five years of age.Brazil, 2010.

Table 4 .
Analysis of the association between the prevalence of dental occlusion by region, location, gender and skin color in children five years of age.Brazil, 2010.