Legal age estimation using developing mandibular third molar roots of various developmental stages in Malaysian population: a CBCT study.

Impacted mandibular third molars (IMTM) are often excluded from dental age estimation due to limited accessibility and morphological variability. This study aimed to develop an age estimation model based on the apical surface area (ASA) of IMTM roots using cone-beam computed tomography (CBCT). A total of 446 CBCT images of Malaysians aged 15-25 years (243 females, 203 males) from Malay and Chinese ethnicities were retrospectively analyzed. ASA measurements were obtained using Mimics and 3-matic software (Materialise NV, Belgium). Impaction levels were classified via a modified Pell and Gregory system, and impaction types using Quek's modification of Winter's classification. IMTM angulation, root number, and orientation across three planes were assessed. ASA means were compared by sex and ethnicity using t-tests, and ANOVA was used to evaluate differences across impaction levels, types, and root numbers. General linear regression was applied to identify significant predictors of chronological age and to develop the model, which was validated using an additional 123 CBCT scans. ASA showed a strong inverse correlation with age (r = -0.73). Significant sex-based differences in ASA were observed (male: p = 0.02; female: p = 0.03), with no significant differences between ethnicities. ASA, sex, number of roots, and impaction type were significant predictors of age. The model achieved an R2 of 0.607 and mean absolute error ranging from 0.85 to 4.87 years across age groups. This study underscores the use of IMTM from CBCT data as a feasible method for legal age estimation in the Malaysian population, particularly in distinguishing juveniles from adults.