Bridging gaps in age estimation: a cross-sectional comparative study of skeletal maturation using Fishman method and dental development using Nolla method among Egyptians

Abstract

Estimating the chronological age of humans is a prevalent need in forensic practice. Comparing the accuracy of different age identification methods helps provide the most reliable method for a specific population. This study aimed to compare the accuracy of age assessments using skeletal maturation and dental mineralization in a sample of Egyptians and to assess if combining both methods yields more precise age prediction. A cross-sectional study included 176 Egyptian children and adolescents aged between 8 and 16 who underwent orthopantomograms and hand-wrist radiographs. All radiographs were scored independently for skeletal maturation using the Fishman method and dental development using the Nolla method. While Fishman and Nolla methods were valid and reliable age predictors with variable sex and age group accuracy in Egyptians, the Nolla method showed superior performance. The Nolla method slightly underestimated the chronological age, while the Fishman method slightly over-estimated it, showing median differences of -0.21 and 0.17, respectively. Correlating the estimated age using the Fishman and Nolla methods and the chronological age showed intraclass correlation coefficients of (0.854 and 0.660) and (0.973 and 0.977) for females and males, respectively (P < 0.001). The model adopting the Nolla score exhibited the highest R² (0.973 and 0.968) and the lowest Akaike information criteria (96 and 106) for females and males, respectively, which is comparable to the model adopting both Nolla scores and skeletal maturation indicators. Therefore, we recommend adopting the model incorporating only the Nolla scores for age estimation without the need for further hand and wrist radiography.

Keywords: Dental age estimation; Egyptians; Fishman method; Forensic odontology; Nolla method; Skeletal age estimation.

Fig. 1

a) Hand-wrist X-ray of a 13.22-year female patient showing different sites (in white) of skeletal maturity indicators (SMI) assessed by Fishman method; capping of epiphyses of the middle phalanx on the fifth finger (SMI = 7), and skeletal age is 12.51 years, b) Panoramic X-ray of the same patient showed different scoring of dental development of the mandibular and maxillary teeth on the left side (except the third molar), marked according to the Nolla method; the total scoring was 138.1 and the calculated dental age was 13 years

Fig. 2

a) Hand-wrist X-ray of a 9.05-year female patient showing different sites (in black) of skeletal maturity indicators (SMI) assessed by Fishman method; the proximal phalanx of the third finger showed equal width of the epiphysis and diaphysis (SMI = 1), and skeletal age is 10.23 years, b) Panoramic X-ray of the same patient showing different scoring of dental development of the mandibular and maxillary teeth on the left side (except the third molar), marked according to the Nolla method; the total scoring was 118 and the calculated dental age was 9 years

Fig. 3

a) Hand-wrist X-ray of a 14.98-year male patient showing different sites (in white) of skeletal maturity indicators (SMI) assessed by Fishman method; capping of epiphyses of the middle phalanx on the fifth finger (SMI = 7), and skeletal age is 14.43 years, b) Panoramic X-ray of the same patient showing different scoring of dental development of the mandibular and maxillary teeth on the left side (except the third molar), marked according to the Nolla method; the total scoring was 137.5 and the calculated dental age was 14 years

Fig. 4

Bland and Altman plots showing differences between a) Fishman skeletal age and chronological age in all participants, b) Nolla dental age and chronological age in all participants. The middle bold dashed line represents the mean difference, and the two extreme bold dashed lines define the limits of agreement

Fig. 5

Graphical representation of the Spearman correlation between a) The chronological age and both of Fishman skeletal age and Nolla dental age in female participants, b) The chronological age and both of Fishman skeletal age and Nolla dental age in male participants, c) The Fishman skeletal age and Nolla dental age in both female and male participants

Fig. 6

Calibration of the proposed models in female participants a) Fishman skeletal age model, b) Nolla dental age model, c) Skeletal maturity indicator model, d) Nolla score model

Fig. 7

Calibration of the proposed models in male participants a) Fishman skeletal age model, b) Nolla dental age model, c) Skeletal maturity indicator model, d) Nolla score model

Fig. 8

Calibration of the proposed models predicting the chronological age using SMI and Nolla Score in a) Female participants, b) Male participants