Population-adapted Nolla method for dental age estimation in Northwestern Romanian children.

OBJECTIVES: Accurate dental age (DA) estimation is essential in pediatric dentistry, orthodontic treatment planning, and forensic practice; however, the applicability of international reference standards varies across populations. This study aimed to evaluate the accuracy of a population-adapted Nolla method for dental age estimation in children from northwestern Romania and to compare its performance with the original approach. MATERIALS AND METHODS: A retrospective analysis was performed on 860 digital panoramic radiographs of children aged 3-15 years. Dental development was assessed using the Nolla staging system, and a third-degree polynomial regression model was developed to estimate chronological age (CA) based on the total Nolla score. Model performance was evaluated using coefficient of determination (R²), five-fold cross-validation, and non-parametric statistical tests. RESULTS: The original Nolla method underestimated CA by approximately 1.5 years. The population-specific model showed strong predictive performance (R² = 0.846; cross-validated R² = 0.84) and close agreement between estimated DA and CA (mean difference 0.000 ± 0.976 years; p = 0.983). Accuracy was stable across most age groups, although larger deviations were observed after 12 years. Girls showed slightly more advanced dental maturation than boys, but differences were clinically small. CONCLUSIONS: The proposed population-calibrated equation eliminates systematic bias and provides a reliable tool for dental age estimation in children from northwestern Romania, although external validation is recommended.