Type of study: cross-sectional
Population: Students from the municipality of Envigado, Colombia, between 8–16 year of age, enrolled in public schools during the second semester of 2011 and the first semester of 2012. Inclusion criterion included children and adolescents with AOB in mixed dentition with fully erupted maxillary and mandibular incisors or in permanent dentition. Signing of an informed consent by the child and legal guardian to participate in the study was required. Exclusion criteria included presence of systemic diseases that cause alterations of normal skeletal development and children with neurological and psychiatric disorders. Presence of orthodontic treatment or history of previous orthodontic treatment, as well as lack of cooperation with the oral evaluation, resulted in exclusion from the study. Students who did not reside in the department of Antioquia were not considered for evaluation. This study was approved by the Ethics Committee from Universidad Cooperativa de Colombia.
Techniques and procedures: At baseline, prior authorization was obtained from the Secretary of Education to visit local elementary schools. Subsequently, a standardization of data collection instruments and a pilot test to evaluate the entire operating process were completed. Children from seven educational institutions were evaluated. Students were visually assessed by two of the researchers in order to identify those who presented AOB. Next, parents or legal guardians of children with AOB were invited to participate and signed an informed consent in the presence of two witnesses. Once approval was obtained, each patient was clinically inspected and overbite was recorded using a Boley gauge.
AOB, as defined by Bishara, is a vertical gap between maxillary and mandibular incisal edges while posterior teeth are in contact [
9]. AOB magnitude was classified as low (up to 1 mm), moderate (1 to 5 mm), and severe (>5 mm) according to Dawson (1974), cited by Iwasa
et al. [
10], considering the degree of amplitude between incisors.
For speech evaluation, VSA designed and adapted a personal evaluation of Spanish spoken in Colombia to avoid misinterpretations or incorrect data analysis. This evaluation was based on the scores provided by Tobias Corredera Sánchez [
11], who describes phonemes, and by Bernal and Baquero [
12], who describe consonant sounds. Evaluation of articulation points and modes was as follows: articulation place: bilabial: / m / p / b /; labiodentals: / f // v /; interdental: / none /; dental: / t / d /; alveolar: / s / n / l / r / rr /; palatal: / y / ll / ch / ñ /; velar: / k / g / j / x /. Articulation mode: Occlusive: / p / b / t / d / k /; fricatives: / f //v// s / y / ll / g / j /; affricates: / ch / x /; nasal: / m / n / ñ /; lateral: / l /; vibrant: / r / rr /.
Speech assessment of each student according to pronunciation of these phonemes was classified as normal, distortion by tongue interposition, distortion by tongue thrust, substitution, or omission. Additionally, articulation organs were assessed by performing the following activities: descent of the lingual apex to the lower lip, movement of tongue tip to reach the lip corners, elevation of the lingual apex to the upper lip, lips in a kiss position, uni and bilateral cheek inflation, right and left movement of lips together, and sweeping the palate with the tongue. As a regular protocol in speech evaluation, these praxias were evaluated for coordination, skill, and symmetry of lingual and labial muscles. Furthermore, palate shape, sensitivity, and rugae thickness (normal, thick or thin) were evaluated.
Palatal rugae are located in the most anterior area of the hard palate. These rugae are anatomical references for the tongue in resting position and play a role during stomatognathic functions. The following definitions were used to describe palatal rugae: tenous palatal rugae, where a mild roughness, corresponding to pressure exerted by the tongue in resting position, was observed; pronounced palatal rugae, where hypertrophic rugae due to lack of stimulation by the tongue during resting position or swallowing were observed [
13].
Palatal sensitivity must be considered since both soft and hard palate are covered by oral mucosa with high numbers of sensory receptors that provide proprioceptive information. Therefore, some aspects, such as appropriate language patterns of the tongue at rest to specify the articulation point, especially for sounds that require contact of various parts of the tongue with the palate, and swallowing function, both in the oral and initial pharyngeal phases [
13], must be evaluated. Palatal sensitivity evaluation consists of carefully applying a soft sensory stimulus in the anterior-posterior direction, which may be linear or circular, and monitoring closely the reaction displayed by the subject to avoid excessive responses, like nausea. The stimulus may be applied at the palatine raphe, or at the palate edges. Parameters to determine sensitivity are: normosensitivity, hypersensitivity, and hyposensitivity [
13].
Sample size: considering that the school population between 8–16 years from the municipality of Envigado for June 2011 was 22.995 and that the prevalence of AOB reported in the literature was 2 % [
14], a sample size of 460 students with ABO was determined as reference for the present investigation. Based on this population and with a 50 % expected proportion of dyslalias, a 95 % confidence level, and a sampling error of 7 %, the calculated sample size of students with AOB was 132.
Analysis Plan: before the analysis, quality control of the database was performed by confirming the information included in the data collection form of 10 % of all the children who presented AOB. The absolute and relative frequencies to describe AOB in school children and its magnitude, dyslalia and types, gender, and grade were reported. Age was described as median with interquartile range (IQR), as it did not follow normal distribution.
To establish whether there was a difference between the magnitude of AOB and the type of dyslalia, Chi square test of independence was carried out. A p value <0.05 was considered significant. Data analysis was performed using the statistical package SPSS version 18.0 (SPSS Inc., Chicago, IL, USA).