Association between malocclusion, tongue position and speech distortion in mixed-dentition schoolchildren: an epidemiological study

Abstract Background Malocclusions are highly prevalent in childhood and adolescence, being considered a public health problem worldwide, in addition to be considered an important predictor in the tongue position and speech disorders. Objective Evaluate the association of malocclusions with tongue position and speech distortion in mixed-dentition schoolchildren from the south of Brazil. Methodology This cross-sectional study was performed using a database of an epidemiological survey realized in the southern of Brazil, in 2015, for evaluating the dental and myofunctional condition of the mixed-dentition from 7-13 years’ schoolchildren. The outcome variables were tongue position and speech distortion, evaluated by a trained and calibrated examiner. Characteristics regarding sociodemographic and oral health measures (Angle’s classification of the malocclusion, overjet, overbite, posterior crossbite and respiratory mode) were also assessed. Poisson regression models with adjusted robust variance were used to evaluate the association among predictors variables in the outcomes. Results are presented as prevalence ratio (PR) and 95% confidence interval (95% CI). Results A total of 547 children were evaluated. Schoolchildren who presented anterior open bite (PR 2.36 95%CI 1.59-3.49) and having oral/oral-nasal breathing (RP 2.51 95%CI 1.70-3.71) are more likely to have altered position of the tongue. Both deep bite and being male represent protection factors for the abnormal tongue position. Regarding speech distortion, deep overbite presents a protective relationship to speech distortion (PR 0.41; 95%CI 0.24-0.71), whereas schoolchildren with posterior crossbite were more likely to present this problem (PR 1.77; 95%CI 1.09-2.88). Conclusion Anterior open bite and posterior crossbite were the malocclusions related to speech distortion and/or altered tongue position. Oral/oral-nasal breathing was also related to myofunctional changes. Deep bite malocclusion was a protective factor for both speech problems and altered tongue position when compared to a normal overbite.


Introduction
Malocclusions are highly prevalent in childhood and adolescence, being considered a worldwide health problem. 1 It also can be defined as a change in growth that affects the occlusion of the teeth. In schoolchildren, malocclusion can lead to non-aesthetic traits, a poor lingual position, and, consequently, changes in speech, which can affect the quality of life. 2,3 In this context, malocclusion is an important predictor to be considered in the tongue position and speech disorders.
Speech is the result of the planning and execution of sequences of movements, which require very accurate neuromuscular coordination. 3 Articulation disorders can begin since childhood, and the prevalence is approximately 22.3% in children of a Brazilian sample. 4 Its etiology comprises genetic factors (11%), environmental (83%) and mixed (6%). 5 Among the factors that influence the articulatory, points' precision are the presence and position of the teeth, mobility of the lips, cheeks, soft palate, tongue and mandible, the intraoral space for articulation and resonance of the sounds. Deviations from chewing, swallowing and breathing functions may also be associated. 6 Moreover, the position of the anterior teeth is one of the main factors that alter the articulation of sounds, since almost 90% of all consonants are performed in this region. 7 Previous studies have investigated the impact of different types of malocclusions on myofunctional disorders. 7, 8,9 The causal explanation between this problem and speech disorders may be related to the anatomical structure of the oral cavity, but it can also be restricted to the type of language itself. 10 Furthermore, the relationship of malocclusion and tongue position can be explained by the Balance Theory, since teeth in the correct position help in the balance between the forces of the tongue and the labio-buccal muscles. 11 Thus, myofunctional therapy in children with malocclusion was able to re-educate tongue positioning at rest, during swallowing and to increase the force of tongue elevation, but it was not able to improve the articulation of some phonemes, 11 suggesting that multidisciplinary treatments, including orthodontic correction, are necessary to fully solve the problem. Between the main types of speech alterations, distortion (anterior and lateral lisp) is due to musculoskeletal, and for this reason, it is one of the interest in this study. 5 Although there are some studies in previous literature that evaluate the relationship among malocclusions with tongue position and speech distortion, 2,6,7,8,9 epidemiological studies with representative samples during mixed dentition using robust analysis methods are still scarce. 2,6,7,8,9 More studies are required to prove stronger associations between tongue-positioning and speech problems with different types of malocclusions, corresponding to the real scenario. It is important for dentists and speech therapists to be aware of malocclusion and craniofacial disturbances that may interfere with the articulation of sounds and tongue position, as such problems may interfere with the interpersonal relationships of individuals throughout their lives. Thus, the study aims to evaluate the association of malocclusions with tongue position and speech distortion in mixeddentition in schoolchildren, in the mixed dentition in the city of Santa Maria, southern Brazil. The hypothesis of the study is that altered tongue position and speech distortion are associated with malocclusion. A random sampling by double stage conglomerate was adopted. In 2014, 10,569 students were enrolled in the 26 public primary schools, where nine of these Association between malocclusion, tongue position and speech distortion in mixed-dentition schoolchildren: an epidemiological study J Appl Oral Sci. 2021;29:e20201005 3/11 schools were randomly selected according to the size of the school and the different administrative regions.

Methodology
From the lists of students, 1,559 children between 7 and 13 years old were invited to participate in the study. The inclusion criteria were being in the mixed dentition phase with the first erupted upper molars. asking the children to count from 1 to 20, telling the days of the week and the letters of the alphabet, later they were asked to describe engravings on a drawing board, so they were classified as absence or as presence of speech distortion, according to MBGR protocol. Phonetic disorders were considered those related to structural issues of the stomatognathic system, more specifically the articulatory points of This study considered two outcomes: (1) speech distortion (absent/present) and (2)   Results From total number of students invited to participate in the study, 948 consented and had the Consent Form signed by parents or guardians (response rate 60.8%). Of those children who agreed to participate, 547 were included in the sample. Figure 1 shows the reasons for sample losses.    Values less than 547 are due to missing data.  there was no association between age and articulation disorders, except for children under 5 years of age.
Furthermore, there was no association between gender and articulation disorders, in agreement with studies by Rabelo, et al. 4 (2011) and Goulart and Chiari 18 (2007).
However, the male gender presented a protective factor for altered tongue position. A previous study showed that sex may affect palatal morphology among individuals and consequently, the tongue position, 20 as well as found in the present study.   Previous studies do not corroborate this result. Whereas Laine, Linnasalo and Jaroma 23 (1987) andLeavy 7 (2016) found no association between these variables, Farronato, et al. 24 (2012) andLubit 25 (1967) found an association between the deep bite and speech distortion. The main differences may be due to methodological, regional and age aspects among the studies. Our findings suggest caution in indicating the treatment of mild to moderate deep bites in young patients in mixed dentition. However, severe deep bites and other associated complications should be indicated for treatment.  considered in this study, which might limit our findings.

Malocclusions of
It can be assumed that, the more specific the diagnosis, the better the interpretation and understanding of the associations will be. Thus, further studies are suggested to assess the association between tongue position, speech distortion and the aforementioned subtypes of malocclusions.
In conclusion, the posterior crossbite was associated with altered tongue position and speech distortion.
Anterior open bites and oral/oronasal breathing mode were also associated with altered tongue position, but do not interfere in speech distortion. Deep bite appears as a protection factor for speech distortion and altered tongue position. These findings reinforce the importance of a multi-professional approach for treating children who have different types of malocclusion.