Incisor Molar Hypomineralization and Quality of Life: A Population-Based Study with Brazilian Schoolchildren

Aim To assess the impact of incisor molar hypomineralization (MIH) on oral health-related quality of life (OHRQoL) according to the perception of students and their parents/caregivers. Materials and Methods This is a cross-sectional population-based study with 463 Brazilian students aged 11–14 years. OHRQoL was measured using the Child Perceptions Questionnaire (B-CPQ11-14ISF: 16) applied to students and the short version of the Parental-Caregiver Perceptions Questionnaire (B-P-CPQ) applied to parents/caregivers. The diagnosis of MIH followed the European Academy of Paediatric Dentistry criteria modified in 2019. Caries experience (ICDAS II), malocclusion (DAI), and socioeconomic and demographic factors were assessed as confounding factors for impact on OHRQoL. Cluster analysis was carried out to dichotomize the negative impact into greater and lesser impact. The chi-square test and Poisson regression were performed (p < 0.05) to verify associations between quality of life and MIH, adjusted for confounding variables. Results The prevalence of MIH was 10.8%. Multivariate regression demonstrated that caries experience was the only oral disease that impacted OHRQoL according to students' self-perception in the functional limitation domain (PR = 1.82; 95% CI = 1.20–2.77) and in the total questionnaire score (PR = 1.59; 95% CI = 1.00–2.51). However, according to the perception of parents/caregivers, in addition to caries experience, which affected OHRQoL in the oral symptoms (PR = 3.57; 95% CI = 1.71–7.414) and emotional well-being domains (PR = 1.71; 95% CI = 1.08–2.69), as well as in the total B-P-CPQ score (PR = 1.67; 95% CI = 1.01–2.76), malocclusion also affected OHRQoL in the social well-being domain (PR = 1.50; 95% CI = 1.07–2.10) and in the total questionnaire score (PR = 1.54; 95% CI = 1.11–2.15). Conclusion According to students and their parents/caregivers' perception, incisor molar hypomineralization did not influence OHRQoL of the studied sample.


Introduction
Quality of life is defined as the perception of well-being and personal and subjective manifestation of good feeling within the sociocultural context in which one lives [1]. During childhood, oral changes can affect the quality of children's systemic health [2]. Additionally, the oral condition also influences the quality of life, which can greatly impact psychological and social aspects [1]. e negative effects of poor dental appearance are irrefutable, also affecting social interaction [3]. e literature reports that enamel defects affect the quality of life of individuals with this condition since enamel defects can modify both aesthetics and the function of teeth [1]. Among these changes, incisor molar hypomineralization (MIH) has stood out and received increasing attention from dentists in several countries [4].
MIH is a qualitative enamel defect of systemic nature affecting one or more permanent first molars, with or without incisor involvement [5]. Clinically, it can vary from the lightest forms, characterized by well-marked opacities to posterior ruptures [5], since in MIH-affected teeth, the enamel is porous and susceptible to fracture [6].
Teeth with MIH generally present greater sensitivity [7], greater tendency to develop carious lesions [8], difficulty in obtaining the anesthetic effect [6,9], and require multiple clinical interventions due to the difficulty in obtaining satisfactory adhesion of restorative materials to the dental substrate [9,10], in addition to longer clinical care [10]. erefore, MIH is associated with a series of oral morbidities, such as tooth hypersensitivity and poor dental aesthetics, affecting the quality of life [11]. e association between the presence of MIH and quality of life has been previously reported in some studies both in Brazil [12,13] and in other countries, such as Colombia [1] and Mexico [14]. However, given the existence of particularities in the occurrence and comorbidities associated with MIH [5,8,15,16], this relationship needs to be investigated in more detail, considering its cultural and socioeconomic diversities [17].
us, in view of the scarcity of literature data, this study aimed to assess the impact of the presence and severity of MIH on the OHRQoL of Brazilian schoolchildren aged 11-14 years.

Study Design and Location.
is is a cross-sectional study conducted in Campina Grande, Paraíba, Brazil. e city has an estimated population of 407,472 inhabitants, Human Development Index (HDI) of 0.72, and Gini coefficient of 0.58 [18]. is study followed recommendations established by the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) [19].

Population and Sample
Calculation. Participants were selected from a total population of 53,596 schoolchildren [18], regularly enrolled in elementary schools in the municipality of Campina Grande, Brazil. Sampling was of probabilistic type by clusters, and for sample calculation, the formula of infinite population was used: n � z 2 × P (1−P)/ FE 2 , where n represents the sample size; z represents the confidence level (95%), standard deviation (1.96); P represents the expected prevalence of the phenomenon to be investigated, 18.4% [12]; FE represents the predicted sample error factor (5%). A correction factor of 1.8 was used, as well as an increment of 10% to compensate for possible losses, with the final sample estimated at 463 students. Two public schools were drawn in each of the six selected urban Health Districts (HD), totaling 12 institutions.

Inclusion and Exclusion
Criteria. All 11-14-year-old schoolchildren who had all first permanent molars fully erupted were included. Schoolchildren with fixed orthodontic appliance at the time of evaluation were excluded [12][13][14], as well as those with special needs (according to parents' reports) who did not cooperate with a clinical examination or were unable to answer the questionnaires.

Calibration.
eoretical and practical calibrations of the three examiners were performed by gold standard researchers with previous experiences in epidemiological investigations to diagnose MIH [20], dental caries [20,21], and malocclusion. For MIH, Cohen's Kappa coefficient was 0.61-0.72 for interexaminer calibration and 0.67-0.83 for intraexaminer calibration.
For dental caries was used the International Caries Detection and Assessment System (ICDAS II) index, examiners took theoretical training online at https://www. iccms-web.com/, and regarding discussions about clinical diagnosis [22], the e practical stage was held in a public school. e interexaminer Kappa correlation values found ranged from 0.80 to 0.90 and intraexaminers values from 0.71 to 0.75.
For malocclusion, criteria proposed by Jenny and Cons [23] and the Brazilian Ministry of Health [24] were used. Cohen's Kappa coefficient was 0.76-0.89 for interexaminer calibration and 0.82-0.94 for intraexaminer calibration.

Data Collection.
Data collection was performed in two stages between September and December 2019. e first stage was performed by parents/caregivers. ey signed the consent form and answered the socioeconomic questionnaire and the Brazilian short form of the Parental-Caregivers' Perceptions Questionnaire (P-CPQ) [25]. e social and demographic questionnaires contained questions concerning parents/caregivers and students such as sex, age, family income (categorized based on the Brazilian monthly minimum wage amount equivalent to US$ 264.00), parents/caregivers' schooling in years of formal study (≤8 years of study/>8 years of study), and family structure (nuclear family structure when the child lives with parents who were married or in a stable union and nonnuclear structure when the child lives with only one single, divorced, or widowed parent), in addition to data on the use of dental services. e reduced form of the B-P-CPQ questionnaire has 13 questions divided into three domains: oral symptoms, functional limitations, and well-being, referring to the last three months. e answer options range from zero to four points (between never and every day or almost every day). "I do not know" responses are allowed and scored 0. e total score ranged from 0 to 52. e higher the score, the higher the impact of oral condition on quality of life [25]. e second stage was performed by the schoolchildren whose parents/caregivers consented to study participation. ey were directed to answer the self-reported 16-item Child Perception Questionnaire (CPQ 11-14 ISF:16) [26] and were clinically assessed.
e Brazilian version of the questionnaire CPQ 11-14 ISF: 16 consisted of 16 items divided into four areas: oral symptom, functional limitation, emotional well-being, and social well-being. Each item addressed the frequency of events in the previous three months. Response options ranged from zero to four points, indicating the occurrence frequency (between "never" and "every day or almost every day"). e total score ranged from 0 to 64, and higher scores denoted a more negative impact of oral conditions on OHRQoL [26].
Before the clinical examination, children were instructed on oral hygiene procedures and received fluoridated toothpaste and toothbrush by means of which their teeth were cleaned by supervised brushing.
Clinical examinations took place in a reserved place in the school, under natural light, with the help of headlamps (JWS Lanternas, São Paulo, SP, Brasil). Researchers used all personal protective equipment, mouth mirrors (Golgran Indústria e Comércio de Instrumental Odontológico, São Caetano do Sul, SP, Brazil), and WHO probes (Trinity Indústria e Comércio Ltda., São Paulo, SP, Brazil) and sterilized in autoclave gauze (Gnatus Equipamentos Médico-Odontológicas Ltda., Barretos, SP, Brasil) to dry teeth, which is in line with infection control standards [27]. e presence of MIH was recorded when at least one first permanent molar was affected by demarcated opacities, ranging from white-cream-yellow-brown, due to posteruptive enamel fractures, by atypical restorations/atypical carious lesions, or when there was an absence of permanent molars due to MIH-all these clinical features with or without the involvement of incisors [20]. MIH severity was classified as mild, only color changes-cream, white, yellow, orange, or brown-and severe-fracture and/or atypical restoration/atypical caries/loss due to MIH [21]. MIH severity was defined by the most severe defect observed in first permanent molars and/or permanent incisors [28].
Schoolchildren were also evaluated to determine their caries experience, malocclusion, and presence of other enamel defects, as they are considered confounding variables [12]. Children were evaluated to determine their dental caries experience according to the International Caries Detection and Assessment System II (ICDAS II) [29]. Dental caries was considered present for ICDAS code >0. Malocclusion was assessed using the Dental Aesthetic Index (DAI). DAI components are divided into three groups: tooth, space, and occlusion and placed in an equation, which classified as absence (DAI ≤25) and presence (DAI >25) of malocclusion [23].

Statistical
Analysis. Data were analyzed using IBM SPSS Statistics (IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp). e internal consistency of the OHRQoL questionnaire was examined by computing Cronbach's alpha coefficients. In order to dichotomize the total score and the domains of the B-CPQ 11-14 ISF:16 and B-P-CPQ instruments in a greater and lesser negative impact on OHRQoL, k-means cluster analysis was performed. Cluster analysis assesses the pattern of responses for each item separately and for the formation of clusters. It considers the correlation between the responses to the instrument and can be valid because there is no cutoff pattern for the sum of questions of B-CPQ 11-14 ISF:16 and B-P-CPQ instruments for the total score and their domains.
A descriptive statistical analysis was performed, and the Kolmogorov-Smirnov test was used to verify the normality of quantitative variables. e chi-square test was used to verify the association between the negative impact on OHRQoL with MIH and confounding variables (caries experience, malocclusion, other enamel defects, and socioeconomic factors). In multivariate analysis, Poisson regression was performed with a robust variance; all variables with p < 0.2 in the bivariate analysis were included in the adjusted multivariate analysis. Prevalence ratios (PR) with the respective 95% confidence intervals (95% CI) were calculated for associations. Variable "MIH in molars" was removed from the adjusted analysis of the B-P-CPQ questionnaire for presenting collinearity with variable "Presence of MIH." A significance level of 5% was adopted.

Ethical Aspects.
is study was approved by the local institutional ethics committee under opinion No. 3.155.847. All study procedures were conducted in accordance with Resolution 466/12 of the Brazilian National Health Council and the Declaration of Helsinki and its subsequent amendments.

Results
A total of 590 children were invited, of whom 463 agreed to participate in the study. e prevalence of MIH was 10.8% (n � 50). Regarding severity, 22 (44.0%) students had a mild degree and 28 (56.0%) had a severe degree. A total of 80.1% of the sample had caries experience, 48.4% had malocclusion, and with respect to other enamel defects, 10.6% was diagnosed with fluorosis, 1.1% with hypoplasia, 0.2% had imperfect amelogenesis, and 4.5% had other types of hypomineralization (Table 1). Tables 2 and 3 show the bivariate analysis between the negative impact of domains and the total score of OHRQoL instruments and independent variables. It was observed that according to the self-perception of students, the presence of MIH, regardless of severity degree, was not associated with OHRQoL. Regarding parents/caregivers' perception, schoolchildren with MIH were associated with a negative impact on OHRQoL in the emotional well-being domain (p � 0.046). In addition, the presence of MIH in molars was also associated with the emotional well-being domain (p � 0.046). Tables 4 and 5 show the crude multivariate models, and Tables 6 and 7 show the final multivariate models of negative impacts of independent variables on self-perceived OHRQoL and OHRQoL perceived by parents, distributed by domains and total scores of the B-CPQ 11-14 ISF: 16 and B-P-CPQ instruments. According to the self-perception of students, the only oral disease that had influence on OHRQoL was dental caries experience, which had 82.8% greater impact rate in the functional limitation domain (PR adjusted � 1.82; 95% CI � 1.20-2.77) and 59% in the total B-CPQ 11-14 ISF:16 score (PR adjusted � 1.59; 95% CI � 1.00-2.51). In addition, females perceived greater impact on OHRQoL in the functional limitation domain (PR adjusted � 1.52; 95% CI � 1.14-2.02), and the lower parental International Journal of Dentistry schooling had impact on emotional well-being (PR adjusted � 1.59; 95% CI � 1.17-2.15) and social well-being domains (PR adjusted � 1.45; 95% CI � 1.01-2.07) ( Table 6).

Discussion
MIH is an enamel defect that has been increasingly studied by the dental community [4]. However, literature is still scarce concerning the impact of MIH on patients' oral health quality.
us, studies of this nature are necessary since they contribute to the planning of oral health promotion programs that are socially appropriate for the target population [17].
Although there is convincing evidence that children with enamel defects experience a variety of psychosocial impacts [3], which can affect their quality of life and cause behavioral problems [6], in this study, the presence of MIH or other enamel defects did not demonstrate impact on OHRQoL from the self-perception of students or the perception of their parents/caregivers. In other studies conducted with Brazilian children and adolescents, MIH had a negative impact on OHRQoL [12,13]. It is believed that the divergence among studies may have occurred due to the cultural differences of the Brazilian population since Brazil is a country with continental dimensions with different cultures depending on the region [30,31]. When considering culturally diverse individuals, it is known that in addition to their different physical, emotional, or social needs, their oral health perceptions may also differ [32].
In this study, caries experience had a higher prevalence when compared to MIH. e occurrence of this disease has been decreasing in recent decades, causing many Western populations to be classified as having a low caries rate; however, its control remains a challenge for many population groups [33]. e literature has shown that caries' presence negatively affects the OHRQoL of patients [2,34,35], which was also observed in this study. is negative impact possibly masked the influence of MIH on the OHRQoL of the population under study.
Dental caries cause functional changes, such as chewing and speaking problems, difficulty sleeping and irritability, also influencing other factors, such as school absenteeism [2]. ese aspects may explain the impact of this condition on the OHRQoL of students in this study, both in their selfperception and in the perception of their parents/caregivers, thus evidencing the harmful effect of caries on the oral health of students [34].
Malocclusion had a negative impact on OHRQoL from the perception of parents/caregivers. is finding is in line with results found in the literature [12,36], which was expected considering that, in this age group, corresponding to  International Journal of Dentistry 5       the beginning of adolescence, social life becomes more intense and appearance tends to become more important [36].
In the present study, female students showed a higher prevalence of impact on OHRQoL in the functional limitation domain of CPQ 11-14 ISF:16 and the social well-being and total B-P-CPQ score from the perception of parents/ caregivers. is finding is similar to that reported in other studies [12][13][14]. Women are more concerned than men about oral health perception [37].
Oral diseases are cumulative and tend to worsen with increasing age [2], justifying the relationship between older ages and greater impact on the social well-being domain of OHRQoL from the perception of parents/ caregivers. us, the diagnosis and treatment of oral changes should occur as early as possible, reducing impacts on students' quality of life [2].
Concerning family income, the reduced availability of access to oral health services is a common reality in populations with low levels of financial resources [14]. Since Brazil is a country with great social disparities, this fact may explain the association between lower family income and a negative impact on the functional limitation of B-P-CPQ on the quality of life of students. is relationship has also been observed in other studies [12,13,34]. e lower the schooling, the greater the chances of presenting inadequate oral health [37,38]. is statement may clarify the association between low schooling and impact on the emotional and social well-being domains of the OHRQoL self-perception questionnaire found in this study. Schooling may also reflect knowledge about the importance and maintenance of healthy oral habits, as well as being strongly associated with oral self-care [37,39]. e cross-sectional design is among the limitations of this study, which analyzes data related to the perceptions of a specific moment [12], not allowing causal inferences. However, the population representativeness through sample calculation, high inter-examiner reliability, the conduction of a pilot study, and the use of validated questionnaires with a high response rate can be highlighted as strengths, aspects that reinforce the study validity.
For the development of public oral health policies from the perspective of a broad and appropriate health concept focused on improving quality of life, it is essential to understand the particularities of a given population [32]. us, the relevance of studies on the perception of OHRQoL in this planning is emphasized, as these strategies must be planned, taking into account the opinion of students and their parents/caregivers.

Conclusion
MIH had no impact on the OHRQoL of schoolchildren aged 11-14 years from the self-perception of schoolchildren or their parents/caregivers.

Data Availability
e data used to support the findings of this study are included within the article.

Conflicts of Interest
e authors declare that they have no conflicts of interest.