Dental age (DA) assessment is a vital component of pediatric dentistry and orthodontics, as it objectively measures a child’s dental development relative to chronological age (CA). Accurate evaluation of DA allows clinicians to determine the optimal timing for interceptive orthodontic treatment, monitor growth and development, and identify deviations from normal maturation patterns, indicating underlying systemic or developmental conditions[1,2]. In particular, DA helps predict the timing and sequence of permanent tooth eruptions, allowing effective treatment planning for space management, impaction management, and prevention of malocclusion progression[3,4]. Its primary clinical significance for pediatric dentists lies in optimizing patient care and tailoring treatment strategies according to each child’s developmental status, although DA estimation has applications in forensic and anthropological contexts.

Several methods have been proposed for estimating the DA, most notably the Demirjian and Willems method, utilizing the developmental stages of teeth on panoramic radiographs. While the Demirjian method is the most widely adopted worldwide, the Willems method was developed to enhance accuracy and reduce the tendency of overestimation, and has been validated in different populations[1,5,6]. Validation studies on Korean juveniles have shown that Willems’ method yields more accurate results than Demirjian’s method, indicating that it is more suitable for Korean children and adolescents[7].

Researchers have explored factors that may influence dental development using reliable and validated DA estimation approaches. DA is influenced by genetic, environmental, and systemic factors. Genetic background plays a major role in determining the pace and pattern of tooth development, while environmental influences such as socioeconomic status, living conditions, and access to dental care can also affect dental maturation [8-10]. Systemic health conditions, such as endocrine disorders (e.g., growth hormone deficiency and thyroid disorders) and metabolic diseases, may accelerate or delay tooth development, and chronic illnesses or long-term medication use can further modify these patterns [11-13]. Nutritional status is another important determinant, as inadequate nutrition during growth can lead to delayed dental maturation, whereas over-nutrition may be associated with accelerated development[14-16]. In the present study, nutritional status was evaluated using body mass index (BMI) as a surrogate marker, enabling the evaluation of its potential association with DA.

Body mass index (BMI) is a widely used anthropometric measure for evaluating the nutritional status of children and adolescents. It is calculated as weight in kilograms divided by height in meters squared and serves as a simple yet effective screening tool for categorizing individuals into underweight (< 5th percentile), normal-weight (5th - 84th percentile), and overweight/obese (≥ 85th percentile) groups based on age- and sex-specific percentile charts. Numerous studies have shown that BMI is closely associated with growth and maturation, with overweight/obese children often exhibiting accelerated skeletal development compared with their normal-weight peers[17]. This acceleration has been attributed to hormonal and metabolic factors, such as elevated leptin, insulin, and insulin-like growth factor 1 (IGF-1) levels, which may influence bone and tooth development[18-21].

However, while the relationship between BMI and skeletal maturity is well established, few studies have explored its impact on dental maturation, and the findings have been inconsistent across populations and age groups. Some studies have reported that children with higher BMI exhibit accelerated dental development, indicating that nutritional status may play a role in dental maturation[15,22-24]. Conversely, other studies have found no significant association between BMI and dental development[15,22,23]. This controversy underscores the need for further research to clarify whether BMI influences DA and whether CA modifies this association. Hence, this study aimed to evaluate the association between BMI and DA among Korean children and adolescents, and to examine the hypothesis that a higher BMI corresponds with advanced dental maturation, an effect becoming more pronounced in older age groups.

This retrospective study was approved by the Institutional Review Board (IRB) of Ajou University Hospital (IRB File No.: AJOUIRB-DB-2025-342) in line with the Declaration of Helsinki (revised 2013).

Our study revealed that a higher BMI was significantly associated with relatively advanced dental maturation in Korean children and adolescents. Specifically, children in the overweight/obese group demonstrated the greatest advancement in DA relative to CA, with DA - CA values significantly higher than those of their normal-weight and underweight peers. Interestingly, no significant difference was noted between the underweight and normal-weight groups. This finding may be explained by the fact that an underweight status, as defined by BMI percentiles, does not necessarily reflect clinically significant undernutrition. Children classified as underweight in our sample may not have experienced sufficient nutritional deficiencies to cause delayed dental development. Furthermore, the relatively small number of participants in the underweight group may have limited the statistical power to detect subtle differences. Similar trends were reported in a previous study in which underweight status did not reliably correspond to delayed DA[26].

Previous studies reported comparable results. For example, Kim et al. explored Korean children and found that only the obese group showed significant advancement in dental maturity compared with the normalweight group, whereas the overweight group did not differ significantly[22]. Contrarily, our study revealed that the overweight/obese group differed considerably from their normal-weight and underweight peers. This discrepancy may be explained by methodological differences (Willems method with DA - CA in our study vs. Demirjian method with maturity scores in Kim’s study), different BMI reference standards (KDCA vs. CDC growth charts), and variations in age distribution (7 - 13 years in our study vs. 5 - 10 years in Kim’s study). Notably, the inclusion of older children in our study may have further highlighted the effect of an elevated BMI on dental maturation. Similarly, Hilgers et al. reported that overweight/obese American children exhibited accelerated dental development compared with their normal-weight counterparts[23]. These findings support the notion that excess body weight is associated with advanced dental maturation, although causal inferences cannot be drawn from this cross-sectional study.

In addition to group differences, our study identified a significant positive correlation between BMI and DA - CA, indicating that an increase in BMI was consistently accompanied by advanced dental development. This finding is broadly consistent with that of Kim et al., who reported a positive relationship between BMI and dental maturity among Korean children[22]. Although their analysis used maturity scores derived from the Demirjian method rather than the DA - CA method, the overall direction of the association was the same: a higher BMI was linked to accelerated dental maturation. Thus, despite the differences in methodology and study design, both studies concluded that BMI was positively related to dental development.

Our regression analysis demonstrated that the BMI z-score and CA were significant factors associated with DA - CA. Notably, the positive effect of the BMI z-score became more pronounced with increasing age. Using BMI z-scores standardized for age and sex, we accounted for individual differences in growth status, thereby reinforcing the robustness of this association. These findings are consistent with those of Mack et al., who employed multivariable linear regression to orthodontic patients and demonstrated that higher BMI percentiles were independently associated with advanced DA, as evaluated using the Demirjian method, even after adjusting for age and sex[24]. Mack et al. reported that BMI is related to skeletal maturation, further supporting the broader influence of BMI on developmental processes. Although their analysis did not incorporate an interaction term, our study demonstrated a significant BMI × age interaction, demonstrating that the effect of BMI on dental maturation is more evident in older children. This highlights a novel aspect of our findings, suggesting that BMI not only contributes independently to dental development but that its influence is age-dependent. Furthermore, a sensitivity analysis using DA as the dependent variable yielded essentially identical results, confirming that our conclusions are robust regardless of whether DA or DA - CA was used. Altogether, these results reinforce the notion that BMI should be considered a relevant factor in dental maturation, beyond the influence of CA.

Overall, boys exhibited significantly higher DA - CA values than girls. This finding contrasts with the conventional understanding that girls generally mature dentally earlier than boys[27]. Caution is warranted when interpreting this result, as the overweight/obese group in our sample, which demonstrated accelerated maturation, contained a disproportionately higher proportion of boys. This imbalance in group composition may have contributed to the observed sex differences, rather than reflecting a true biological reversal of the typical maturation pattern. It should also be noted that the Willems method employs sex-specific conversion scores for each tooth stage, with boys generally assigned slightly higher scores than girls. While this adjustment was designed to enhance the accuracy of age estimation, it may have influenced the observed sex differences in DA - CA in our study. Therefore, part of the apparent male predominance could be attributed to the methodological features of the Willems system, in addition to the sample composition. Age-stratified analysis further highlighted divergent trajectories between the sexes. Boys tended to demonstrated decreasing DA - CA values with advancing age, whereas girls exhibited an increasing trend, and this divergence became more apparent during the pubertal period. These sex-specific trajectories, particularly the earlier acceleration observed in girls, may be related to the differences in the timing of pubertal onset.

In our tooth-level analysis, statistically significant differences were observed in several teeth when comparing the overweight/obese and underweight groups; however, the effect sizes were small (r = 0.17 - 0.20), which limits their clinical significance. The second molar was the only tooth that revealed a significant difference between the overweight/obese and normal-weight groups (r = -0.122, 95% CI: -0.20 to -0.04, p= 0.009). Although this effect size was small, the second molar is of particular biological and clinical interest because it is a late-developing tooth that coincides with the pubertal growth spurt. Therefore, the observed advancement in the second molars of overweight/obese children may reflect both the natural timing of pubertal development and the additional influence of obesity-related endocrine changes. Nevertheless, the small magnitude of the effect indicates that these findings should be interpreted with caution, and further studies are required to confirm their clinical relevance. Furthermore, unequal age distributions among BMI groups should be considered. Children in the overweight/obese group tended to be older on average than those in the underweight group, which may have partly contributed to the observed differences in dental maturation. Although our regression analysis was adjusted for CA, the imbalance in age distribution across BMI categories indicates that group comparisons should be interpreted with caution.

The underlying hormonal and metabolic mechanisms may explain these patterns including the overall association between elevated BMI and advanced dental maturation. Obesity alters the endocrine milieu and amplifies hormonal changes during puberty, potentially influencing dental and skeletal maturation[28]. Puberty is a critical developmental period during which profound hormonal changes occur, and children with a higher BMI often experience earlier pubertal onset[20]. In our study, DA - CA values were the highest at age 7, declined at age 8, and then showed divergent trajectories between the sexes. Girls exhibited a relative rebound in DA - CA from ages 9 to 11, consistent with the earlier onset of puberty, whereas boys continued to show decreasing values until age 12, followed by a slight recovery at age 13. These sex-specific patterns indicate that puberty may interact with BMI to influence dental maturation, particularly in later-developing teeth such as the second molars, which are significantly more advanced in the overweight/obese group.

Biologically, obesity alters the endocrine milieu through increased levels of leptin, insulin, and insulin-like growth factor 1 (IGF-1), which stimulate bone turnover and may accelerate skeletal growth[29,30]. Leptin, secreted by adipose tissue, acts as a permissive signal for pubertal initiation, whereas IGF-1 promotes somatic and dental tissue development[21,28]. Recent evidence also indicates that leptin receptors are expressed in dental and craniofacial tissues, where leptin stimulates odontoblastic differentiation and dentin mineralization, whereas IGF-1 contributes to dentinogenesis and pulp cell proliferation[31,32]. Together, these pathways provide a plausible mechanism whereby a higher BMI may contribute to earlier pubertal onset and accelerated dental development. Previous studies have shown that obese children experience an earlier onset of puberty and advanced bone age than their normal-weight peers, and these effects have been attributed to metabolic and hormonal changes associated with excess adiposity. Shalitin and Phillip highlighted the role of obesity and leptin in promoting pubertal growth, whereas De Groot et al. revealed that IGF-1 and leptin were significant determinants of advanced bone age in obese children [18,20,21]. These findings support the interpretation that the accelerated maturation we observed in the overweight/obese children, particularly pubertal girls and late developing teeth, may reflect the combined influence of obesity-related endocrine changes and pubertal timing. Although these hormonal pathways provide a plausible explanation for the observed patterns, it should be emphasized that our study did not include the direct measurement of hormonal or biochemical markers. Therefore, these interpretations remain hypothetical and should be interpreted cautiously.

Several methodological and demographic factors may explain why our results differ from those of previous studies that reported no significant association between BMI and dental development, such as those conducted in Brazilian, Iranian, and Sudanese populations[26,33,34]. First, most of these studies used the Demirjian method, which tends to overestimate DA and may be less sensitive to subtle differences in BMI [35]. Conversely, we employed the Willems method and calculated the DA - CA, which has been validated as more accurate for Korean children and provides a clinically intuitive measure of dental advancement[7]. Second, the age range of the study population varied considerably between the studies. Studies that included very young children (as early as 3 - 5 years old) may have failed to capture the influence of BMI, which becomes more evident around the pubertal growth period. Third, the definitions of the BMI groups differed across studies. In this study, BMI was standardized using 2017 KDCA growth charts to generate age- and sex-specific z-scores, that were used for both group classification and regression analyses. Conversely, other studies have applied the WHO z-scores, unspecified CDC/WHO cut-off values, or even unstandardized absolute BMI values. Such heterogeneity may have led to misclassification and obscured the true associations. Fourth, many studies that reported null results relied primarily on group comparisons or simple correlations, which may not adequately account for confounding variables or the nonlinear nature of growth. Our use of multivariable regression, including an interaction term, enabled us to identify not only the independent effects of BMI and age but also their age-dependent interaction. Fifth, differences in sample composition may have reduced the statistical power of earlier studies, particularly when underweight or overweight groups were underrepresented.

Although previous studies have produced inconsistent results, our findings consistently demonstrated that BMI is associated with accelerated dental maturation in Korean children and adolescents. This consistent pattern underscores the clinical relevance of BMI in growth and treatment planning. The clinical implications of these findings are significant in pediatric dentistry and orthodontics. Estimating DA is critical for determining the timing of interceptive treatment, growth modification, and overall treatment planning. Our study demonstrated that overweight and obese children exhibited advanced dental maturation compared with their normal-weight peers. In clinical practice, treatment may need to be initiated earlier in these children to match their accelerated developmental stages. However, it is important to note that conventional DA standards are based on general population averages and may not fully reflect the accelerated maturation observed in the overweight/obese group. If the BMI is not considered, there is a risk of misinterpreting the developmental stage and determining the optimal treatment timing. Therefore, incorporating BMI into DA evaluation can help clinicians achieve a more accurate and individualized assessment of growth and development, leading to improved treatment planning and outcomes.

Although these results provide valuable insights, several limitations should be acknowledged. Most importantly, the retrospective cross-sectional design limited our ability to draw causal inferences, and the study population was drawn from a single institution in Korea, which may have reduced the generalizability of the findings. While we observed significant associations between BMI and dental maturation, it remains unclear whether increased BMI directly accelerates dental development or whether both are driven by other underlying factors, such as hormonal changes or genetic predisposition. Longitudinal studies are required to track individual changes in BMI and dental maturation over time to clarify the temporal and potentially causal nature of this relationship. Second, DA was evaluated using only the Willems method. Although this method has been validated and shown to be more accurate in Korean children than the Demirjian method[7], its reliance on a single method restricts its comparability to other populations and study designs. Future research could strengthen the external validity by employing multiple age estimation methods or combining radiographic assessment with skeletal maturation indices, such as CVMS. Third, skeletal maturity indicators were not evaluated in this study. Dental and skeletal maturation do not always progress in parallel, and considering only DA may not fully capture the overall biological development of children. Including skeletal maturity assessments, such as hand-wrist radiographs or cervical vertebral maturation stages, would provide complementary information and enable direct comparisons between dental and skeletal maturation in relation to BMI. Future research incorporating both dental and skeletal indices will help to clarify whether BMI exerts similar or divergent effects on different aspects of biological maturation. Fourth, the BMI was utilized as a surrogate measure of nutritional status. While BMI is widely employed in epidemiological studies, it cannot distinguish between fat and lean mass and does not account for variations in body composition [36-39]. Moreover, BMI does not reflect the hormonal or biochemical changes associated with obesity, such as leptin, insulin, and IGF-1 levels, which may directly influence dental development. Importantly, our study did not include direct measurements of hormonal or biochemical markers. Therefore, the discussion of potential endocrine mechanisms remains speculative and should be interpreted with caution. Incorporating body composition measures (e.g., DXA and bioelectrical impedance) or biochemical markers in future studies will provide a more precise understanding of the biological mechanisms linking obesity to dental maturation [40]. Fifth, the distribution of participants across BMI groups was imbalanced, with boys overrepresented in the overweight/obese group. This imbalance may have contributed to the higher DA - CA values observed in boys overall and limited our ability to determine whether BMI exerts sex-specific effects on dental maturation. Sixth, dental development is influenced by multiple factors, including genetic background, nutritional status, and endocrine regulation. Although our study highlights the association between BMI and dental maturation, other factors may play a more substantial role in explaining individual variation. As we did not have information on these variables, our ability to isolate the independent contribution of BMI was limited. Future research should incorporate skeletal maturity indices, advanced body composition measures such as DXA or BIA, and biochemical markers, along with large-scale multicenter and longitudinal investigations. Such approaches are essential for validating the findings, enhancing external validity, and establishing normative references across diverse populations.

This retrospective study demonstrated that a higher body mass index was significantly associated with relatively advanced dental maturation in Korean children and adolescents. Overweight and obese participants exhibited more advanced dental development than their normal-weight peers. Regression analysis confirmed that BMI was an independent predictor of DA even after adjusting for CA. The effect of BMI on dental maturation was more evident in the older children, highlighting age-dependent interactions. Although causality cannot be inferred from this cross-sectional study, these findings indicate that BMI may serve as a supplementary indicator when evaluating DA and planning orthodontic treatments. Incorporating BMI as an adjunctive factor into DA assessment may provide a more individualized and accurate approach to growth evaluation, thereby supporting better treatment timing and outcomes.