Influence of malocclusion on oral health-related quality of life in children: a seven-year cohort study

ABSTRACT Objective: To assess the influence of early childhood malocclusion on oral health-related quality of life (OHRQoL). Methods: 7-year cohort study involving 639 preschoolers (1 to 5 years) who had been evaluated initially with a survey conduced in 2010. Children completed the Brazilian version of the Child Perception Questionnaire (CPQ8-10) to assess OHRQoL during the follow-up period. Exploratory variables were collected at baseline, including the presence and severity of malocclusion (overjet and lip coverage). Socioeconomic characteristics, oral health behavior, and patterns of dental attendance were also investigated. A multilevel Poisson regression model was used to fit the association between malocclusion and OHRQoL. With this approach, incidence rate ratio (IRR) and 95% confidence intervals (95% CI) were calculated. Results: A total of 449 children were re-evaluated (follow-up rate, 70.3%). The prevalence of accentuated overjet and inadequate lip coverage was 13.5% and 11.9%, respectively. The mean (±SD) CPQ8-10 score was 10.57±10.32. The presence of inadequate lip coverage was associated with higher overall mean CPQ8-10 scores (IRR 1.51; 95% CI 1.29-1.77), and social well-being, emotional well-being, and functional limitation domains. Children with accentuated overjet (>3mm) also demonstrated higher overall scores on the CPQ8-10 than their normal counterparts. The presence of this condition also influenced the oral symptom (IRR 1.29; 95% CI 1.08-1.53) and emotional well-being (IRR 1.30; 95% CI 1.02-1.66) domains. Conclusion: Results of the present study suggest that early childhood malocclusion is a risk factor for low OHRQoL in future.


INTRODUCTION
The current definition of oral health reflects physiological, social, and psychological aspects important to the quality of life. 1 The concept of oral health-related quality of life (OHRQoL) comprises a multidimensional and subjective perception of well-being. It is not restricted to only the physical and psychological effects of treatments, but also involves several interconnected spheres of physical, familial, and environmental questions. 2,3 Notwithstanding, OHRQoL has been defined as a complement to clinical measurements to document the impact of oral disorders on an individual's activities of daily life. 4 Malocclusion is defined as a change in growth and development that affects tooth occlusion. It is considered to be a public health problem and is highly prevalent. Data from the most recent Brazilian national oral health survey revealed that approximately 37.6% of 12-year-old children exhibited some type of malocclusion. 5 Non-aesthetic occlusal characteristics, especially in children, have been associated with unfavorable social interactions, impairing social and psychological well-being. 6 Previous studies have assessed the association between occlusal disorders and OHRQoL of children and adolescents. 7-10 Children with malocclusion report worse OHRQoL than their normal (i.e., non-malocclusion) counterparts. [9][10][11] It occurs especially when malocclusion is located in the Tondolo Junior J, Knorst JK, Menegazzo GR, Emmanuelli B, Ardenghi TM Influence of malocclusion on oral health-related quality of life in children: a seven-year cohort study anterior region, such as anterior open bite and accentuated overjet. [9][10][11] Despite this evidence, most studies have been cross-sectional in design, which prevents the assessment of causality. Therefore, longitudinal studies would be more useful in evaluating the influence of the cumulative effect of early malocclusion exerts on OHRQoL. 12 Knowledge of changes in the dental transition stage could be important to the implementation of preventive approaches for children in this age group. Furthermore, it has been shown that malocclusion and its consequences are not only reflected in childhood, but may persist throughout life. 13 Thus, the aim of the present cohort study was to assess the influence of early childhood malocclusion on OHRQoL. Our hypothesis was that children who experienced malocclusion in early childhood will report a worse OHRQoL than their normal counterparts.

STUDY DESIGN AND SAMPLE
An epidemiological oral health survey was performed in 2010 during the Children's National Vaccination Day, in Santa Maria, Brazil. Santa Maria is a city located in southern region of Brazil.
In 2010 had an estimated population of 263,403, which included 27.520 children <6 years of age. A random sample group was selected from among all children who attended health centers in the municipality on the National Children's Vaccination Day. Tondolo Junior J, Knorst JK, Menegazzo GR, Emmanuelli B, Ardenghi TM Influence of malocclusion on oral health-related quality of life in children: a seven-year cohort study 6 A total of 639 preschool children from all administrative regions of the city were orally examined by 15 examiners who were previously trained and calibrated. A multistage sampling considered all health centers with a dental office as primary survey units, and 15 out of 28 health centers were randomly selected.
Each health center is responsible for vaccinating children living in that area. Caregivers of the children completed a semi-structured questionnaire designed to collect data regarding socioeconomic status, health behaviors, and the pattern of use of dental services. Details regarding the methodology followed in this first phase have been published. 14 At follow-up (on average, 7 years later), sample planning was based on all children who were previously evaluated (n = 639). The assessment of malocclusion, the main predictor of this study, was obtained through baseline examinations. 14 The children were examined in health centers in dental chairs with conventional lighting, using a flat dental mirror, periodontal probe (CPI, "ball point"), and damp gauze. The variables used to measure occlusal disturbances were overjet and lip coverage. Overjet was measured in millimeters and, for analysis, was dichotomized as present (>3mm) or absent (<3mm). Lip coverage was recorded and analyzed as adequate (when the lips covered the anterior teeth completely at rest) or inadequate (when most of tooth crown was exposed and visible). 14 Tondolo Junior J, Knorst JK, Menegazzo GR, Emmanuelli B, Ardenghi TM Influence of malocclusion on oral health-related quality of life in children: a seven-year cohort study 8 Socioeconomic characteristics of the sample were recorded at baseline and included sex, annual household income, household overcrowding, mother's education, and dental service attendance. The annual household income was collected in Real (R$-Brazilian cure -R$3.80 it was equivalent to approximately USD$1.00) and then categorized into approximate quartiles. Household crowding was evaluated according to the ratio of number of individuals to the number of rooms in a house (except the bathroom) and transformed into quartiles for analysis. Maternal schooling was collected as years of study, and categorized as completed elementary school (≥ 8 years) and those with < 8 years of education. Dental service attendance was measured according to the reason the child visited the dentist in the previous 6 months and was categorized as routine (score = 0), non-routine (score = 1), and no visit (score = 2). The feasibility of the questionnaires used was previously assessed in a sample of 20 parents during the calibration process. These parents were not part of the final sample.

STATISTICAL ANALYSIS
Data were analyzed using STATA version 14.0 (StataCorp LLC, College Station, TX, USA). The primary outcome measure of this study were overall and domain-specific CPQ8-10 scores. were assessed using the chi-squared test. Descriptive statistics were used to describe the characteristics of the sample at baseline (T 1 ) and at follow-up (T 2 ).

The differences between participants and non-participants
Adjusted multilevel Poisson regression models were used to fit the association between early childhood malocclusion characteristics (overjet and lip coverage) and OHRQoL at follow-up.
The multilevel structure of analysis considered individuals (level 1) nested into 15 health centers (level 2). The results are presented as incidence rate ratio (IRR) and respective 95% confidence interval (CI). Variables with p-value <0.20 in the unadjusted analysis were considered in the multivariable models.

ETHICAL CONSIDERATIONS
The study protocol was approved by the Committee of Ethics in Research of the Federal University of Santa Maria (CAAE 54257216.1.0000.5346). All children consented to participate, and their parents or legal guardians signed an informed consent form.

RESULTS
Of 639 children who were examined at baseline, 439 were re-examined at follow-up (70.3% follow-up rate). The reasons for non-participation were refusal to participate in the study (n=9) or the child could not be found (n=181). Comparing participants' and non-participants' baseline characteristics (chi-squared    13 The unadjusted analysis between the malocclusion variables and OHRQoL is found in Table 3. The results of the multilevel adjusted analysis for possible confounding covariates in association with malocclusion and OHRQoL are shown in Table 4.

DISCUSSION
The present study assessed the influence of malocclusion on OHRQoL in a cohort of children. The main finding was that malocclusion assessed according to inadequate lip coverage and accentuated overjet (>3mm) had a negative impact on children's OHRQoL. This result supports the hypothesis that early childhood malocclusion is a risk factor for low OHRQoL over time. Our findings corroborate previous studies reporting that individuals with malocclusion experienced higher impact on OHRQoL than those without malocclusion. 8 Individuals with accentuated overjet (>3mm) demonstrated higher overall mean CPQ8-10 scores. An analogous observation was found for the oral symptom, functional limitation, Changes in dentition occur slowly and over the developmental stages of childhood and adolescence, and are often associated with non-nutritive sucking habits, such as finger or pacifier sucking, and prolonged use of bottle-feeding, which can cause occlusal and aesthetic changes produced by unfavorable positioning of the teeth and should be avoided. 24 To this end, the World Health Organization recommends that breastfeeding should be exclusive in the first six months, promoting improvement in the physical, mental and psychological health of children and reducing the need for non-nutritive sucking habits. 25 It is recommended that the time limit for the elimination of pacifiers be 3 years of age. 26 Therefore, early treatment may provide an important benefit for some children who experience teasing and negative stereotyping, and early orthodontic intervention to improve dentofacial aesthetics may improve a child's social interactions. 24 In addition, study psychosocial factors in early adolescence is important. Adolescence is a period of transition and it is characterized by physiological, behaviors and social changes. 27 Through psychosocial theory, it is known that individuals with oral injuries can present physical and psychological pains and sufferings, contributing to stress, anxiety and worse OHRQoL. 28 These consequences may interfere in health behaviors in this age group as in the practice of deleterious habits and self-care in health. 28 Furthermore, it has been shown the changes at this stage and its consequences are not only reflected in childhood, but may persist throughout life. 13 This study had limitations and strengths. One limitation was that we used a quantitative questionnaire. However, studies combining quantitative and qualitative measurements via questionnaires and interviews could provide more sensitive information as to how malocclusions in early childhood can affect a child's OHRQoL years later. Future studies encompassing more malocclusion characteristics are required. In addition, for this study, data were gathering in 15 out of 28 health centers, which may affect the extern validity of the study.
However, the sampling considered all health centers with a dental office as primary survey units, which were equally dis-

CONCLUSION
Our findings support the hypothesis that anterior segment malocclusions have a significant influence on OHRQoL in children.
The recognition of the changes established in the transitional stage from primary to permanent dentition, as well as the importance of preventive approaches for children in this phase of growth, when their occlusion has not yet reached maturity, makes it relevant to study this age group. An early diagnosis may facilitate the prevention of malocclusions through interceptive orthodontics, taking into account the promotion of health and OHRQoL of children.