Comparison of the population occlusal characteristics in 3 Brazilian regions

The objective of this work was to determine the prevalence of individual traits of malocclusion in a sample of three Brazilian regions orthodontic patients and to detect interregional population differences in the prevalence of certain occlusal characteristics.  The present study was based on the examination of dental casts, intraoral photographs and panoramic radiographs of 947 orthodontic patients from 3 cities: 363 from Fortaleza (CE), 270 from Maringá (PR) and 314 from Bauru (SP), respectively, representing the Northeast, South and Southeast Brazilian regions. The relationship of the first maxillary and mandibular molars according to Angle’s classification, overjet, overbite, crowding, posterior crossbite and maxillary median diastema were examined. The chi-square and ANOVA tests were used to determine potential differences in the distribution of malocclusion when stratified Brazilian regions. Class I malocclusion was found in 499 (52.69%), Class II in 395 (41.71%) and Class III malocclusion in 53 (5,59%) subjects of all examined. Deep overbite (3.59%), midline diastemas (5.17%) and posterior crossbite (4.75%) were observed more frequently in Bauru; however, in Maringá, normal overbite (13.3%) and open bite (4.75%) were more prevalent. The results of this study showed that Class I malocclusion was the most prevalent, followed by Class II and Class III malocclusions. These occlusal relationships evaluated in the three Brazilian regions follow the same pattern of frequency as the result presented by the general population of the sample.


Introduction
Epidemiological studies are important tools for the knowledge of the treatment needs and evaluating the established measures for these treatments. The health authorities recommend the carrying out of epidemiological surveys of the main oral diseases at the ages of 5, 12 and 15 years old and in the age groups of 35-44 and 65-74 years in a period between Development, v. 9, n. 10, e1839108586, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8586 4 5 and 10 years (Frazão et al., 2002). The knowledge of oral health status in different population groups based in epidemiological surveys is fundamental for the actions proposals development adapted to their needs and risks as well as the comparisons possibility that allow the evaluation of these actions impact in the individual's life (Frazão et al., 2002;Freitas et al., 2002).
The establishment of malocclusions classification in Brazil is of great difficulty because Brazil presents great racial miscegenation, being necessary to consider the regional differences (Ribas et al., 2004). Therefore, it is necessary to characterize the differences in the distribution of malocclusion types among genetically well-defined populations and those that underwent interracial crosses to compare the presented predominance and to identify the current malocclusion pattern in the population to be studied.
Based on the observation of these regional singularities in Brazil, whether economic, cultural and/or genetic or the few researches that performed a comparative analysis in the epidemiology of the malocclusion among Brazilian regions, the objective of this study was to compare the prevalence and the most frequent occlusal traits, besides verifying if there are regional differences in the prevalence of such occlusal characteristics in three different Brazilian cities.

Methodology
This retrospective (Pereira et al., 2018)  This was a quantitative study (Pereira et al., 2018), since its objective was to obtain a sample of the distribution of malocclusions in 3 Brazilian regions.
The sample was obtained from 947 completes pretreatment orthodontic files (lateral cephalograms, panoramic radiographs, dental casts and intra and extraoral photographs) of 3 post-graduation centers, distributed as follows: 363 orthodontic files from Uningá, units of These orthodontic files included subjects in the deciduous, mixed and permanent dentition with at least three and a maximum of 56 years old. They included subjects of both sexes, as well as the ethnicities: white, black and mestizo, except for the indigenous one. Research, Society and Development, v. 9, n. 10, e1839108586, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8586 5 As a methodology for evaluating dental casts and radiographs, a previously calibrated single evaluator (M.A.) performed the examinations and analyzes of the orthodontic files, using a pencil, rubber, digital caliper, millimeter ruler and noted in a specific card prepared to this propose. The examiner selected each pair of dental casts and evaluated them in occlusion.
The following measures were made and then compared in the dental casts: molar relationship (as described by Angle (Angle, 1899)), dental spacing (multiple spaces between teeth), anterior open bite (when maxillary and mandibular incisors do not contact vertically), dental crowding (crooked teeth), overjet (horizontal distance between upper and lower teeth), overbite (amount that the maxillary incisors overlap the mandibular incisors) and crossbite.
The panoramic radiographs were also evaluated, performed in a dark room using the negatoscope.
The ANOVA statistical test was used in addition to the Chi-square tests. All statistical analyses were performed with Statistica software (Statistica for Windows 7.0; Statsoft, Tulsa, USA). Results were considered statistically significant at P<0.05.

Results
Class I molar (mesiobuccal cusp of the maxillary first molar occludes in the mesiobuccal sulcus of the mandibular first molar) relationship was the most frequent (499 subjects, 52.69%) while Class II (mesiobuccal cusp of the maxillary first molar occludes mesially to the mesiobuccal sulcus of the mandibular first molar) was found in 41.71% (395 subjects) and Class III (mesiobuccal cusp of the maxillary first molar occludes distally to the mesiobuccal sulcus of the mandibular first molar) was found in 5.59% (53 subjects) (Table 1).

Discussion
Since malocclusion affects a large segment of the population, it is, by definition, a public health problem (Massler & Frankel, 1951), being this way of interest of the community to know its frequency. A systematic and well-organized dental care program for any target population in a community requires some basic information, such as the prevalence of the condition to be assessed (Aikins & Onyeaso, 2014).
When evaluating the Brazilian regions separately, it is observed that the prevalence of Angle Class I, II and III occlusal relationships follow the same order of frequency as the result presented by the sample population as a whole. There was no statistically significant difference between then. Martins et al. (1998) stated that the low values for the Class II frequency are a classification methodology problem, where the canines can have a class II relationship and the molars are in a Class II relationship, leading to a classification error.
Dental crowding was found in 69.9% of the cases, similar to other studies (de Oliveira Waked et al., 2010;Freitas et al., 2002;Martins & Lima, 2009). However, other studies found different results. Vellapally et al. (2014) stated that dental crowding is the most common malocclusion trait among adolescents (84.9%), while Thilander (Thilander et al., 2001) found a dental crowding incidence of 52.14% in Colombian adolescents. When evaluating the studied sites individually (Fortaleza-CE, Maringá-PR and Bauru-SP), it can be observed that the crowding prevalence follows the same order of frequency as the result presented by the sample population as a whole (Table 1).
Deep overbite was found in 6.12 of the total collected sample. This result was similar to that obtained by Ahangar-Atashi et al. (2017), whose result was 5.17%. However, some authors have found different results, where sometimes achieving higher (de Oliveira Waked et al., 2010;Horowitz, 1970;Martins & Lima, 2009;Thilander et al., 2001) or lower (Borzabadi-Farahani et al., 2009) results. This difference among the results is probably due to the methodology used for the deep overbite diagnosis. In this research, we performed a methodology similar to that used by Gandini et al. (1994), which divided the deep overbite index into normal, moderate and accentuated and then classified as accentuated, overbites greater than 6mm. Evaluating the studied sites individually (Fortaleza-CE, Maringá-PR and Bauru-SP), deep overbite was more prevalent in Bauru (Table 2).
Open bite was found in 11.29% of the total collected sample, similar to that obtained by some authors (de Oliveira Waked et al., 2010;Freitas et al., 2002;Thilander et al., 2001).
Nevertheless, other authors (Ahangar-Atashi et al., 2017;Borzabadi-Farahani et al., 2009;Martins & Lima, 2009;Mtaya et al., 2009) found different results. These different results are probably due to age differences in the samples. Some studies were limited to younger patients and others with no age limit. In our study, Maringá obtained the highest percentage of open bite (Table 3). The sample obtained from Maringá-PR has the lowest mean age among the three cities from this study, and according to Freitas et al. (2002), some cross-sectional studies Development, v. 9, n. 10, e1839108586, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8586 have shown a decrease in the frequency of some malocclusions due to occlusion maturation, among them the anterior open bite. The main reasons for these malocclusions decrease are the growth and dental changes and the decrease of deleterious habits that occur with aging.
One can say that a higher prevalence of open bite in Maringá could be attributed to the lower mean age of the sample in this locality, but the conclusion is that there is a higher prevalence in that city since there were no significant differences in the three evaluated regions (Tables 2 and 3).