Crypt-to-Tooth Ratio of the Permanent Second Mandibular Molar as an Indicator of Chronological Age in Egyptian Children: A Radiological Study

Background: Dental development is a reliable method to estimate the chronological age in forensic investigations. Crypt-to-tooth ratio (CTR) has emerged as a quantitative tool for age estimation as tooth crypt decreases in size during tooth development. However, its applicability has not been explored in Egypt. Using dental radiographs, this study aimed to evaluate the reliability of CTR of the permanent mandibular second molar as an age estimation tool for Egyptian children and establish population-specific reference data.Methods: This retrospective cross-sectional study analyzed 200 digital panoramic radiographs from Egyptian children aged 5–17 years (97 males, 103 females; mean age 11.14 ± 3.09 years). CTR was calculated using ImageJ software by measuring the crypt area and mineralized tooth area. Reliability was assessed through re-measurement of 20 radiographs. Results: A Strong negative correlation was observed between chronological age and CTR values (r = -0.975, p <0.001). Mean CTR decreased consistently from 2.66 ± 0.28 in the youngest group to 1.00 ± 0.06 in the oldest group. No significant sex differences were found. Linear regression yielded the equation: age = 19.95 - 5.6 (CTR) with R² = 0.856 and standard error of 1.175 years. Validation testing showed no significant difference between estimated and chronological ages (p = 0.670), with most estimates falling within ± 2 years of actual age.Conclusion: CTR of the mandibular second molar demonstrates high reliability for age estimation in Egyptian children and provides a valuable population-specific tool for forensic applications with acceptable accuracy ranges.