Unhealthy dietary habits and sedentary behavior drive untreated dental caries among adolescents: A population-based study

Dental caries has historically been recognized as one of the greatest global public health challenges, affecting populations of all ages and social backgrounds. It is one of the leading non-communicable chronic diseases, with impacts that go beyond oral health, affecting overall well-being, learning ability, and even the social integration of affected individuals¹. The condition is multifactorial in nature, influenced by several elements such as diet composition, access to oral healthcare, and education on oral hygiene². Adolescents with severe dental caries report negative impacts on their self-esteem, such as difficulties in social interactions, particularly in the school environment. This underscores the importance of disease prevention and the promotion of self-care for oral health in this age group³.

In Brazil, the situation is also concerning. Data from the latest national oral health survey, SB Brasil, indicate that over 80% of Brazilian adolescents have had at least one tooth affected by caries⁴. Although the country has implemented oral health policies focused on prevention and treatment, such as the “Brasil Sorridente” Program, many young people still face difficulties accessing quality dental services. Factors such as social inequality, lack of resources in rural or underserved areas, and parents’ low educational levels directly affect the oral health of adolescents⁴.

Studies show that the distribution of dental caries among adolescents is heterogeneous, with the disease being more severe in socially disadvantaged classes. Furthermore, variables such as the Municipal Human Development Index (MHDI) and the ratio of dentists to the population are also related to the number of decayed teeth. In regions with lower MHDI and a smaller proportion of dentists per capita, the prevalence of dental caries is higher⁵. Adolescence is a critical period in human development, marked by profound physical, emotional, and social changes. During this phase, many young people tend to neglect oral hygiene, either due to lack of proper information, peer influence, or reduced regular follow-up by an oral health professional⁶.

Additionally, dietary choices—often rich in sugars and processed foods—increase the risk of dental caries. This context makes adolescence a particularly vulnerable stage for the onset and progression of caries, a condition that, if left untreated, can lead to serious complications such as intense pain, abscesses, and even tooth loss⁷. Systematic reviews⁸ have found an association between screen time/TV viewing and the consumption of unhealthy foods among adolescents, showing that the presence of screens during meals increases the intake of sugar-rich foods and sugary beverages, which can lead to a higher prevalence of caries in this age group⁸. Thus, the high prevalence of untreated dental caries in adolescents highlights the need for a more integrated and comprehensive approach that considers not only individual behaviors but also the social and economic determinants that shape access to and the quality of oral health care². Moreover, theoretical frameworks that consider social determinants of health⁹ are essential to understand patterns of unhealthy food consumption and their association with dental caries. Rather than attributing outcomes solely to individual behavior, such frameworks help contextualize how socioeconomic conditions may influence dietary habits and oral health risks. Indeed, the recent SB Brasil 2023 survey represents a major effort in monitoring oral health conditions at the national level. However, it did not collect information on important behavioral risk factors such as dietary intake and sedentary behavior. This perspective supports a more nuanced interpretation to explore the influence of these variables on untreated dental caries among adolescents, especially when examining disparities among adolescents.

The objective of this study was to analyze factors associated with untreated dental caries in 12-year-old adolescents living in the five largest cities (> 80,000 inhabitants) in the state of Mato Grosso do Sul, Brazil. Specifically, the study aimed to: identify behavioral, socioeconomic, and contextual factors associated with the prevalence of untreated dental caries in adolescents.

This is a cross-sectional, school- and population-based study derived from the SBMS 2018/2019 epidemiological survey, which was conducted in the five largest cities in the state of Mato Grosso do Sul with over 80,000 inhabitants: Campo Grande, Dourados, Três Lagoas, Corumbá, and Ponta Porã, between April 2018 and February 2019. These cities were selected because they are the most representative of the state’s four territorial macro-regions^10,11.

This study analyzed the factors associated with untreated dental caries in 12-year-old adolescents. Data were collected on caries experience according to the criteria of the World Health Organization (WHO), as well as behavioral data from the adolescents. The theoretical framework of the social determinants of oral health guided all analyses⁹.

Sample size

To estimate the sample size for dental caries, we used the mean and standard deviation of the DMFT index from the Central-West region based on SBBrasil 2010¹² data (mean = 2.63; SD = 1.81), with a 95% confidence level (Z = 1.96), a margin of error of 0.10, a design effect (deff) of 2.0, and a 30% estimated non-response rate. A two-stage cluster sampling design was applied, with cities as primary sampling units and municipal public schools as secondary units. Following national survey guidelines, 32 schools were selected in Campo Grande and Dourados by random draw, while all schools were included in Corumbá, Três Lagoas, and Ponta Porã, totaling 115 participating schools.

The initial sample calculation indicated the need for 520 students. Considering an estimated 35% school-level refusal rate (mainly due to lack of authorization), we adjusted the number of students per school from five to seven. To ensure sufficient representation and buffer for losses, this number was rounded up to 10 students per school^10,11.

Study participants and data collection

To select study participants, up to ten 12-year-old adolescents per classroom were selected, drawn from a list provided by the school administration. Students who had transferred to other schools or were not attending at the time of the study were excluded from the sample. Epidemiological data were collected through a questionnaire delivered by the local coordination team to the parents or guardians of the adolescents, which included sociodemographic questions. After returning the completed questionnaire at school, the adolescents answered another questionnaire about their dietary habits. Five dental teams in each city, composed by a dentist and an annotator, received explanations with 32 h of practical training, based on consensus. The intra- and inter-examiner reliability test showed a Kappa coefficient of 0.73^10,11.

Outcome

The outcome variable was the Decayed teeth(D ≥ 1), a component of DMFT (decayed missing and filling tetth, as recommended by the World Health Organization(WHO)¹³. A CPI probe was used for clinical caries examination on tooth surfaces, considering caries in the presence of a fissure, pit, or smooth surface of a tooth with a visible cavity or softened tissue at the base of the enamel, enamel discoloration, or a temporary restoration (except for glass ionomer). Descriptive proportion analyses were performed to establish associations between the independent variables and the outcome.

Independent variables

The variables were dichotomized: sex (female or male) and self-reported race/skin color (White, Brown/mixed-race, Asian, Black, or Indigenous). Per capita household income was categorized as below or equal/above the poverty line, considering the Brazilian economic context in 2018. Household income, as reported by parents or guardians through a structured questionnaire. Respondents were asked to indicate the total monthly household income, categorized into brackets based on the number of Brazilian minimum wages (e.g., ≤ 1 minimum wage; >1 to 2; >2 to 3; >3) and 1 MW was considered R$954/month (corresponding to US$ 308,8 dollars). Parental education level was subdivided into 1–4 years of schooling and more than 4 years^10,11. Adolescents reported the use of dental floss (yes/no).

For the weekly frequency of unhealthy food consumption, an instrument recommended by the Brazilian Ministry of Health was used, covering five food groups with the following options: (1) French fries, packaged chips, and fried snacks; (2) hamburgers and processed meats; (3) salty crackers or packaged savory snacks; (4) sweet cookies, filled cookies, candies, and chocolate (bars or bonbons); and (5) regular soda¹⁴. The average weekly frequency was obtained by summing and dividing by five, classifying unhealthy food consumption as: low (up to 2 times/week), moderate (2 to 4 times/week), and high (4 or more times/week)¹¹.

Sedentary behavior (more than 2 h/day) was assessed using an instrument translated and validated Rey lopez et al.¹⁵ and validated to the Brazilian adolescents population¹⁶ based on the total time adolescents spent in four sedentary domains: TV, video games, internet use, and remaining seated. Participants selected one of seven categories that described their daily routine (0 min; less than 30 min; 30 min to 1 h; more than 1 h to 2 h; more than 2 h to 3 h; more than 3 h to 4 h; and more than 4 h per day). Total hours spent in sedentary behavior during weekdays were multiplied by five, and weekend hours by two, then divided by seven (total days of the week) to obtain a weekly average¹¹. To analyze toothbrushing frequency, responses were categorized as brushing two or more times/day versus once or not at all. The water fluoridation variable was based on measurements from the 2017 Vigiflúor survey¹⁷, which provides the most up-to-date data on public water supply fluoridation in the state of Mato Grosso do Sul.

Analytical framework

The analytical framework for this study was informed by the social determinants of health approach⁹, organizing variables into three domains: sociodemographic, behavioral, contextual. Sociodemographic factors included sex, self-reported race/skin color, household income, and parental education. Behavioral variables comprised toothbrushing frequency, use of dental floss, unhealthy food consumption, and sedentary behavior. At the contextual level, water fluoridation was included based on municipal coverage. The outcome was defined as the presence of at least one untreated decayed permanent tooth (D ≥ 1), assessed by clinical examination. Table 1 presents the complete list of variables and their operational definition.

Statistical analysis

Univariable and adjusted multilevel logistic regressions were performed to test the association between untreated dental caries and behavioral, sociodemographic factors and contextual factors. In the unadjusted models, the relationship of each variable with the presence of dental caries was examined. Variables included in the adjusted models were those with statistical significance or with p < 0.20. Sensitivity analysis (Appendix table) tested for effect modification between ethnicity (White vs. non-White) and socioeconomic status (poverty) using additive interaction metrics. These included the Relative Excess Risk due to Interaction (RERI), the Attributable Proportion (AP).

Model performance and fit

Specifically, we present the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) for model comparison (null and adjusted). We also report the Intraclass Correlation Coefficient (ICC) to quantify the variance attributable to clustering by city. In addition, we assessed multicollinearity among covariates using the Variance Inflation Factor (VIF), and all variables included in the final model presented VIF values below the commonly accepted threshold of 2.

Ethical aspects

The study was approved by the Human Research Ethics Committee of the Federal University of Mato Grosso do Sul (CAAE number 85647518.4.0000.0021). All participants signed an informed assent form, and their guardians signed the informed consent form.

The study population consisted of 615 twelve-year-old schoolchildren from 69 schools that agreed to participate in the study. The prevalence of untreated dental caries at age 12 was 25.3% (95% CI: 18.8–33.1). To facilitate the analysis, the following tables present the results obtained, addressing various factors associated with untreated dental caries in adolescents, including socioeconomic, behavioral, and contextual determinants. Table 2 presents the descriptive characteristics and proportions for the state of Mato Grosso do Sul (SBMS Study 2018–19) among 12-year-old children and untreated dental caries. According to the variables analyzed, regarding ethnic groups, Black children (n = 32) had the highest prevalence of untreated caries (57.9%) compared to White (n = 270; 20.9%), Mixed-race (n = 266; 28.3%), Asian (n = 24; 23%), and Indigenous (n = 6; 50%) children.

Regarding sex, the prevalence of untreated caries was similar between groups: 24.2% in females (n = 315) and 26.9% in males (n = 300). Regarding per capita income, families above the poverty level (n = 376) had a lower prevalence of caries (23.3%) than those below the poverty level (n = 216; 32.4%). Concerning parental education, adolescents whose parents had more than four years of schooling (n = 234) had a lower prevalence of caries (22.6%) compared to those whose parents had up to four years of schooling (n = 381; 26.1%). A higher prevalence of caries was also observed among adolescents with high unhealthy food consumption (more than 4 times/week; n = 217; 40.4%), followed by moderate consumption (2 to 4 times/week; n = 197; 31.4%) and low consumption (up to 2 times/week; n = 168; 9.4%). In terms of brushing frequency, adolescents who brushed their teeth only once a day or not at all (n = 234) had a higher prevalence of dental caries (33.6%) compared to those who brushed two or more times a day (n = 318; 18.7%). Regarding flossing, adolescents who reported not using dental floss (n = 272) showed a higher prevalence of dental caries (32.4%) than those who did use it (n = 280; 18.6%).

Analysis of water fluoridation status, a contextual variable, showed that areas with access to fluoridated water had a lower prevalence of untreated caries (n = 411; 21.6%) compared to areas without access (n = 204; 42.3%). Additionally, adolescents with sedentary behavior (more than 2 h/day using the internet, gaming, sitting, or watching TV) had a higher prevalence of caries (n = 251; 44.6%) compared to those without such behavior (n = 338; 25.7%). Table 2 below presents the multilevel logistic regression models for the prevalence of untreated caries according to covariates.

In the adjusted models, sociodemographic characteristics such as income above the poverty level [OR = 0.55 (95% CI: 0.33–0.91)], access to fluoridated water [OR = 0.58 (95% CI: 0.28–0.99)], and brushing more than twice a day [OR = 0.54 (95% CI: 0.32–0.91)] were associated with untreated dental caries as protective factors(Table 3).

Risk factors included unhealthy food consumption [OR = 5.00 (95% CI: 2.21–11.62)] and sedentary behavior [OR = 1.56 (95% CI: 1.00–2.52)]. Unhealthy food consumption was a highly significant variable, increasing the likelihood of untreated caries by five times. Water fluoridation was significant, reducing the likelihood of untreated caries by 42%. Additionally, per capita income was significant, with a 45% protective effect. The ICC (Intraclass Correlation Coefficient) refers to the variance partition coefficient, indicating how much of the variation in caries prevalence is attributable to differences between cities. Thus, the context matters, with a 21.1% (95% CI: 11.7–35.2) variation in caries prevalence between municipalities(Table 3).

This study highlights sedentary behavior and unhealthy food consumption as behavioral factors influencing the prevalence of untreated dental caries among Brazilian adolescents, emphasizing that caries remains a significant public health issue in this population. Its multifactorial etiology encompasses behavioral, socioeconomic and contextual components as access to water fluoridation.

As a cross-sectional study, this research has inherent limitations, notably the inability to infer causality and the lack of data on residential mobility of participants, which could not be controlled. However, the use of validated instruments, both nationally and internationally, particularly for assessing sedentary behavior, enhances the reliability of our findings and supports their potential relevance for informing public policies^15,16. A major strength of this study is its representativeness: it covered over half the population of Mato Grosso do Sul, a key Brazilian state in the Midwest region, significant for its agribusiness sector, which contributes around 25% to Brazil’s GDP. Unlike many previous studies that focus solely on screen time, this research assessed four dimensions of sedentary behavior using the HELENA study instrument, known for its internal reliability¹⁴. To our knowledge, this is the first complex oral health survey in Brazil to examine the association between sedentary behavior and dental caries, with unhealthy food consumption as a potential mediator¹¹. Dietary data were collected using the SISVAN questionnaire, a validated tool from the Brazilian Ministry of Health.

Untreated dental caries is a socially determined disease influenced by factors such as high-sugar diets, inadequate oral hygiene, low socioeconomic status, and lack of water fluoridation¹⁸. Adolescents from families below the poverty line experienced greater disease burden, likely due to fewer dental visits and limited access to hygiene products^11,19. Broader factors such as obesity, stress, and adverse environments also impacted oral health and should be addressed in preventive strategies²⁰. Sedentary adolescents with poor diets were more likely to have untreated caries, while physical activity emerged as a protective factor, associated with lower sugar intake, healthier lifestyles, and reduced caries and periodontal issues²⁰.

Educational level is another key determinant: lower parental education, especially maternal, was associated with reduced awareness of oral health and poorer hygiene practices^6,21,22. Infrequent brushing and flossing were strongly linked to caries prevalence, underscoring the importance of school-based and family-oriented educational interventions¹⁹. Caries negatively affects adolescents’ quality of life, leading to pain, low self-esteem, concentration difficulties, and impaired school performance. Inadequate access to dental care in low-income settings can exacerbate these issues and contribute to long-term oral and general health consequences²³. Access to fluoridated water was associated with lower disease burden, reaffirming its role as a cost-effective preventive measure⁶. However, fluoridation alone is insufficient—equity-oriented policies that address structural barriers in education and healthcare are essential to reducing oral health disparities⁶.

Evidence from Brazil’s Family Health Strategy (ESF-SB) shows that expanding oral health team coverage increases service utilization among adolescents¹⁰. However, inequities persist: wealthier, white adolescents more often use private preventive services, while lower-income, non-white adolescents rely on public services mainly for curative care. Expanding preventive coverage in public schools and promoting health education campaigns can help bridge this gap¹⁰. Other studies have linked excess screen time and high consumption of sugary snacks to higher DMFT scores, with water fluoridation again demonstrating a protective effect^11,18. Furthermore, income trajectory influences caries over time—adolescents from high-income families have better outcomes, while those from low-income households face persistent disease, despite access to universal healthcare²⁴. This highlights the need for early, equitable access to prevention. Longitudinal evidence shows that childhood caries is a strong predictor of adult disease, reinforcing the importance of preventive action across the life course^14,25.

Our findings reinforce the association between unhealthy dietary habits, sedentary behavior, and the prevalence of dental caries in adolescents. In particular, frequent consumption of sweets, soft drinks, and processed foods has been significantly linked to both the occurrence and severity of caries, emphasizing that not only the quality but also the frequency of cariogenic food intake are key determinants of oral health in this age group. Likewise, sedentary behavior, such as excessive screen time involving television, smartphones, or computers, has been associated with higher caries rates and poorer periodontal outcomes. Importantly, screen overuse often co-occurs with unfavorable eating patterns, further compounding the risk of dental disease^26,27,28.

Moreover, studies conducted in high-income settings have shown that caries development is part of a broader set of co-occurring risk behaviors. For example, research from the United Kingdom identified that lower socioeconomic status, reduced use of dental services, inadequate oral hygiene, high sugar intake, alcohol consumption, and tobacco use tend to cluster among adolescents with untreated caries. These findings highlight the complex interaction between social vulnerability and behavioral risk factors, which together increase the likelihood and severity of dental disease²⁹. Similarly, our study identified multiple interconnected determinants of caries, underscoring the importance of adopting a comprehensive approach that addresses both direct and indirect risk factors in adolescent oral health.

Variance Inflation Factor (VIF) values for all independent variables were low (mean of 1.23), indicating no evidence of multicollinearity in the final model. Additionally, interaction analysis using additive measures (RERI, AP), presented in Appendix Table, did not show significant effect modification between race and income in the sensitivity analysis. These findings support the robustness of the multivariable model and the independent contribution of each covariate. Notably, unhealthy food consumption remained a significant factor associated with untreated dental caries, even after adjustment for sociodemographic and contextual variables.

In conclusion, this study confirms that dental caries in adolescents is shaped by multiple, intersecting determinants. Socioeconomic status, access to healthcare, poor hygiene habits, and sugar-rich diets significantly influence caries prevalence. Socially vulnerable adolescents are disproportionately affected, demanding public policies that expand access to care and incorporate preventive strategies such as water fluoridation. Oral health teams must adopt interdisciplinary approaches, promoting healthy diets and physical activity alongside oral hygiene.