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Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children
Legal Medicine xxx (2015) xxx–xxx
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Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children Nursel Akkaya a,⇑, Hümeyra Özge Yilanci b, Dinçer Göksülük c a
Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hacettepe University, 06100 Sıhhiye, Ankara, Turkey _ Izmir Dental Training Hospital, 35260 Konak, Izmir, Turkey c Department of Biostatistics, Faculty of Medicine, Hacettepe University, 06100 Sıhhiye, Ankara, Turkey b_
a r t i c l e
i n f o
Article history: Received 8 December 2014 Received in revised form 4 March 2015 Accepted 7 April 2015 Available online xxxx Keywords: Forensic science Forensic odontology Age estimation Children Adolescents A repeated measures ANOVA
a b s t r a c t The aim of this study was to evaluate applicability of five dental methods including Demirjian’s original, revised, four teeth, and alternate four teeth methods and Willems method for age estimation in a sample of Turkish children. Panoramic radiographs of 799 children (412 females, 387 males) aged between 2.20 and 15.99 years were examined by two observers. A repeated measures ANOVA was performed to compare dental methods among gender and age groups. All of the five methods overestimated the chronological age on the average. Among these, Willems method was found to be the most accurate method, which showed 0.07 and 0.15 years overestimation for males and females, respectively. It was followed by Demirjian’s four teeth methods, revised and original methods. According to the results, Willems method can be recommended for dental age estimation of Turkish children in forensic applications. Ó 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Age estimation is one of the important applications both for deceased and living people in Forensic sciences. Estimating chronological age is necessary for identification of criminal cases, victims of mass disasters and investigations of human remains in archeological studies. Age determination for living individuals is required to assess criminal responsibilities, which is crucial to decide whether accused individual or victim is below or above the age threshold for that criminal law. It is also frequently used for civil purposes and social issues such as school attendance, immigration, adoption, marriage and incorrect birth records [1,2]. Dental age estimation can be made using a number of methods, which are based on developmental features [3,4] or age-related changes in teeth, such as attrition, secondary dentin apposition, periodontosis, cementum apposition, root resorption, and root transparency [5,6]. Other approaches for age estimation include the evaluation of racemization of aspartic acid in dentine [7], telomere shortening in pulp DNA [8], the amount of radiocarbon in enamel [9]. ⇑ Corresponding author at: Hacettepe Üniversitesi Disß Hekimlig˘i Fakültesi, Ag˘ız, Disß ve Çene Radyolojisi Anabilim Dalı, 06100 Sıhhiye, Ankara, Turkey. Tel.: +90 3123052205; fax: +90 3123113741. E-mail addresses: [email protected] (N. Akkaya), ozgeerbudak@yahoo. com (H.Özge Yilanci), [email protected] (D. Göksülük).
Dental development is widely used as an indicator of chronological age in sub-adults. Dental age estimation methods and other methods including bone development, secondary sex characters, stature or weight can be applied separately or together to estimate a minor’s age [3,10]. Since dental development is less affected by environmental factors in comparison with the growth of the skeletal, somatic or sexual systems, dental age estimation methods are more reliable and accurate than the other methods, especially for children under 10 years old [1,11,12]. Several methods have been introduced for dental age estimation based on radiographic tooth development [1]. Demirjian dental development method [3,13] is one of the most commonly used techniques for age estimation in children [14]. Demirjian et al. [3,13] established four methods for dental age estimation based on eight calcification stages from calcification of the cusps to closure of the apex. The original Demirjian technique includes seven left mandibular teeth except for third molar. Disadvantage of this method is to require the existence of all seven teeth. In case of bilaterally absence of teeth, the method cannot be used. In 1976, Demirjian and Goldstein [13] presented three more methods: revised seven teeth method; four teeth method (M2, M1, PM2, PM1); and alternate four teeth method (M2, PM2, PM1, I1). In these methods, each tooth is rated based on its developmental stage, each stage is allocated a score, then sum of each score (maturity score) are converted to dental age by using standardized tables or percentile curves (50th percentile) for each gender separately.
http://dx.doi.org/10.1016/j.legalmed.2015.04.003 1344-6223/Ó 2015 Elsevier Ireland Ltd. All rights reserved.
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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N. Akkaya et al. / Legal Medicine xxx (2015) xxx–xxx
Demirjian method is based on the radiographs of French– Canadian children. The technique has been widely applied in other populations, but revealed general overestimation in most of the studies [15–26]. Several studies have pointed out that generation of new standard curves, which are specific to the population, is required [20,21,23,27,28]. Based on Demirjian scoring system, Willems et al. [29] proposed a new method that includes new tables for each sex and age score, which directly expresses in years. The adapted method was validated and resulted in more accurate dental age estimations in a Belgian Caucasian population. Previous studies generally used Demirjian’s seven teeth methods [16–26]. Also in a few researches, Demirjian’s four teeth methods were investigated [15,30,31]. In Turkish population, previous studies showed overestimation of the chronological age, which were conducted based on seven teeth methods of Demirjian [27,32–35]. Demirjian’s four teeth methods and Willems method have not been tested before in Turkish children and adolescents. Therefore, the aim of this study was to evaluate the applicability of Demirjian’s four methods; original, revised, four teeth and alternate four teeth methods, and Willems method for age estimation in a sample of Turkish children.
2. Materials and methods Investigational protocol described herein was approved by NonInterventional Clinical Researches Ethics Board at Hacettepe University. The records of the patients in the age group of 2– 16 years, who visited the Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hacettepe University between 2011 and 2012, were reviewed. Panoramic radiographs of the patients without any obvious developmental anomalies were selected from the patients’ records. The radiographs that were unclear and that bilaterally showed teeth with gross pathology, root canal treatment, shape and position anomalies and bilateral absence of the teeth in the mandibula were excluded. The study sample comprised of digital panoramic radiographs from a total of 799 individuals (412 females, 387 males) aged 2.20–15.99 years. The chronological age of each subject was calculated by subtracting the date of the panoramic examination from the date of birth in decimal system. For all five methods (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method and D: Demirjian’s alternate four teeth method, and E: Willems method), each of the seven left permanent teeth of the mandible was assessed, and maturity scores were determined according to developmental criteria (A–H) by two observers. The right permanent teeth were evaluated when the left side was unsuitable for the evaluation. Demirjian’s sex-specific numerical scores assigned to each tooth, and they were summed up to obtain an overall maturity score, for four methods separately. These scores were subsequently converted into a dental age using published conversion tables for original method and maturity percentile curves at the 50th percentile for the other three methods. For Willems method, adapted maturity scores of seven teeth were summed up and directly obtained dental age. Before analyzing data, inter and intra-observer agreement was evaluated via Cohen’s Kappa statistic to ensure that there was no significant measurement error. To evaluate intra-observer reliability, 71 radiographs were randomly selected from the different age groups and re-examined six months after the initial scoring by two observers separately. Similarly, randomly selected 94 panoramic radiographs, seven teeth for each, were examined to evaluate inter-observer reliability. To compare dental methods among gender and age groups, a repeated measures ANOVA was performed on age differences, i.e. residuals, which is the magnitude of
difference between estimated age and chronological age. The response variable was symmetrically distributed among comparison groups, however; statistical tests rejected normality as a result of large sample size [36,37]. Previous studies showed that ANOVA is robust to moderate departures from normality and can be used when sample size is large enough [38,39]. Pairwise comparisons between methods were also provided. For each tooth, the amount of kappa was estimated above 0.7. The overall agreement, which was estimated from 658 different evaluations within 94 radiographs for each tooth, was obtained as 0.824. Intra-observer agreement values were 0.950 and 0.878. Table 1 shows that from both inter and intra-observer results, the agreement of measurements was found to be almost perfect according to the categorization of kappa statistic proposed by Fleiss [40]. Although the measuring bias was highly decreased, there still existed imbalanced structures within subgroups. As expected, the number of observations within younger subsets was extremely low. Therefore, age interval 2.99–5.99 was collected to a single group and introduced into ANOVA as <5.99.
3. Results Gender and age distributions of sample are presented in Table 2. Table 3 gives descriptive statistics for age residuals of each method independent from age groups. Willems method (E) provided the best result for both males and females. This result can be graphically seen from Fig. 1. All methods overestimated the chronological age and the amount of overestimation was slightly higher for females (Fig. 1). However, the performance of each method was found to be different for changing age groups according to ANOVA results given in Table 4. The results of repeated measures ANOVA showed that higher order interactions were significant for both within and between subject effects. Hence, we can conclude that each method gave different results for each gender and age groups (Fig. 2). For patients aged below 5.99, each method gave almost similar results for females and males whereas there were differences among methods within gender. We also demonstrated pairwise comparisons in Table 4. Since Willem’s method was found to be more accurate than Demirjian’s four methods, only the pairwise comparisons versus Willem’s method with false discovery rate (FDR) adjusted p-values were given in Table 5. For females, Willems method was significantly diverse from Demirjian’s methods at all ages. However, for males, Demirjian’s four teeth (C) and alternate four teeth methods (D) mostly gave similar results with Willem’s method (E).
Table 1 Inter/intra-observer agreement values. Tooth No.
I1 I2 C PM1 PM2 M1 M2 Total
N
94
658
Inter-observer
N
Kappa
p
0.890 0.915 0.708 0.761 0.697 0.910 0.812 0.824
<0.001
71
<0.001
497
Intra-observer Observer 1
Observer 2
Kappa
p
Kappa
p
0.965 0.862 0.940 0.926 0.982 0.977 0.930 0.950
<0.001
0.888 0.863 0.856 0.829 0.847 0.896 0.915 0.878
<0.001
<0.001
<0.001
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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N. Akkaya et al. / Legal Medicine xxx (2015) xxx–xxx Table 2 Gender and age distribution of sample. Age groups
Boys (N)
Girls (N)
Total (N)
2.20–3.99 4.00–4.99 5.00–5.99 6.00–6.99 7.00–7.99 8.00–8.99 9.00–9.99 10.00–10.99 11.00–11.99 12.00–12.99 13.00–13.99 14.00–14.99 15.00–15.99 TOTAL
5 9 7 10 19 31 43 45 41 22 39 50 66 387
3 5 3 10 11 24 36 23 22 30 52 88 105 412
8 14 10 20 30 55 79 68 63 52 91 138 171 799
4. Discussion The aim of this study was to evaluate the applicability of Demirjian’s four methods and Willems method for age estimation of Turkish children. In this study, all of the five methods were demonstrated to be both gender and age sensitive. Demirjian’s original method showed the greatest overestimation of chronological age by 0.66 and 0.52 years for females and males, respectively. Demirjian’s revised method, four teeth methods and Willems method followed it. For Willems method, differences between chronological and estimated age were 0.15 and 0.07 years for females and males, respectively. Willems method was more accurate Demirjian methods, which was consistent with previous studies [16,17,19,24,25,41–43]. Several previous studies have used original and revised Demirjian methods in different populations [15–26]. The results showed wide variations between different populations and also different groups of same population [20,44]. Considerable numbers of studies using Demirjian method reported overestimation in their population [15–28,32–35], although underestimation was also reported [45]. Studies using original and revised Demirjian methods in Turkish children from different geographic regions showed generally overestimation in dental age [27,32–35,44], as in this study. In Northern Turkish children, Tunç and Koyutürk [27] found that the mean difference between chronological and dental ages ranged from 0.36 to 1.43 years for males and from 0.50 to 1.44 years for females. In Eastern region of Turkey, Çelikog˘lu et al. [32] found that the mean difference between chronological and dental ages ranged from 0.4 to 1.3 years in males and from 0.2 to 1.9 years in females. In another Turkish study, Kırzıog˘lu and Ceyhan [34] showed that Demirjian method gave an overestimation of 0.52 years and 0.75 years for males and females, respectively. Although our results are consistent with these studies, the
Table 3 Descriptive statistics for age residuals. A
B
C
D
E
Female (n = 412)
Mean Median Std. Dev.
0.666 0.660 1.058
0.623 0.630 1.064
0.567 0.550 1.023
0.612 0.590 1.001
0.157 0.180 1.158
Male (n = 387)
Mean Median Std. Dev.
0.526 0.540 1.077
0.328 0.400 1.063
0.209 0.260 1.091
0.180 0.300 1.109
0.076 0.190 1.023
A: Demirjian’s original method. B: Demirjian’s revised method. C: Demirjian’s four teeth method. D: Demirjian’s alternate four teeth method. E: Willems method.
Fig. 1. Error bars of age residuals for each method within gender (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method D: Demirjian’s alternate four teeth method, and E: Willems method).
Table 4 Results of repeated measures ANOVA. df
SS
MS
F
p
Within subjects Method Method ⁄ gender Method ⁄ age Method ⁄ age ⁄ gender Error (within)
4 4 48 48 3092
54.574 5.439 18.892 16.05 314.1
13.64 1.360 0.394 0.334 0.102
134.3 13.38 3.874 3.292
<0.001 <0.001 <0.001 <0.001
Between subject Gender Age Gender ⁄ age Error (between)
1 12 12 773
16.655 207.507 125.644 3813.49
16.655 17.292 10.470 4.933
3.376 3.505 2.122
0.067 <0.001 0.014
minor differences in findings may be explained by variations of study design, statistical methods, sample size, age groups, age and sex distribution of the study population, and performance of observer [46]. Environmental factors such as socioeconomic status, nutrition, dietary habits and life-style may have also contributed to these differences. As mentioned by several articles the accuracy of the age estimation methods should be verified in different populations and the studies should be done to create population-specific databases [20,23,27,28,34,45]. Therefore, some authors have calculated new scores [19–21,29,47]. Willems et al. [29] firstly modified Demirjian method for the Belgian Caucasian population. In their study, Willems et al. estimated chronological age with minimal errors (a median of 0.1 years for males and 0.2 years for females), but these were not statistically significant. It was reported that Willems method provided more accurate age estimation than the Demirjian’s methods [16,17,19,24,41–43,48,49]. Our results also support this fact. Liversidge et al. [50] suggested that advancement in dental maturation may be explained by positive secular trend in growth and development. Improvement of the life conditions with better nutrition and the decline in the severity and frequency of diseases in childhood for many populations may accelerate dental development [11]. Willems et al.[29] published their revised maturity scores almost 25 years later than the study of Demirjian et al. [3,13]. Therefore, Willems et al.’s maturity scores were closer to the present time. Also in Turkish children and adolescents, positive secular changes in growth were demonstrated [51].
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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N. Akkaya et al. / Legal Medicine xxx (2015) xxx–xxx
Fig. 2. Age residuals of the methods for age and gender groups (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method, D: Demirjian’s alternate four teeth method, and E: Willems method).
Table 5 Pairwise comparisons (Demirjian’s vs. Willem’s Method – FDR adjusted). Gender
AE BEà CE§ DE((
Female Male Female Male Female Male Female Male
<5.99
0.000 0.000 0.001 0.000 0.002 0.004 0.007 0.007
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
6.99
7.99
8.99
9.99
10.99
11.99
12.99
13.99
14.99
15.99
0.001 0.006 0.022 0.006 0.046 0.008 0.194* 0.071*
0.002 0.010 0.034 0.017 0.001 0.416* 0.002 0.371*
0.001 0.017 0.005 0.092* 0.000 0.416* 0.000 0.092*
0.000 0.002 0.000 0.000 0.000 0.563* 0.000 0.009
0.000 0.000 0.000 0.000 0.000 0.324* 0.000 0.226*
0.000 0.000 0.000 0.000 0.000 0.099* 0.000 0.027
0.000 0.000 0.000 0.735* 0.000 0.463* 0.000 0.767*
0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.338*
0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.123*
0.000 0.000 0.000 0.005 0.000 0.640* 0.000 0.468*
*
à §
p > 0.05. Demirjian’s original method versus Willems method. Demirjian’s revised method versus Willems method. Demirjian’s four teeth method versus Willems method. (( Demirjian’s alternate four teeth method versus Willems method.
All the methods tested in this study showed similar results for males and females whose ages below 5.99. Our findings are consistent with the previous studies [52,53] which stated that there was no difference in the timing of dental development between males and females up to 5–6 years of age. According to our results, generally, performance of each method increased slightly with age, and was better in males. The differences between chronological and estimated age showed systematic decrease between the ages of 6 and 12 years and then drastically changed for the age of 13 years in males, whereas these differences were unsteady with firstly increasing and then decreasing values for the ages from 10 and 15 years in females. This may be due to fluctuations in pubertal growth period of these ages. A mean age difference of ±1.0 year is considered accurate in forensic anthropology [47], but an acceptable range is defined ±0.5 year in some studies [31,54]. However, ideally age estimation method should arrive at an age as accurate as possible [17,43]. Among all of the five methods tested in this study, Willems method gave relatively better results than the others. Demirjian’s four teeth methods showed lower overestimation than the seven teeth
methods, as in other studies [42,54]. Moreover, Demirjian’s four teeth and alternate four teeth methods gave similar results with Willem’s method at most of ages in males. Therefore, Demirjian’s four teeth methods can be improved with further studies to estimate age in case of tooth absence for the evaluation.
5. Conclusion Based on the results of this research, it was concluded that Willems method is more suitable than Demirjian methods for dental age estimation. Therefore, this method can be used for forensic procedures in Turkish children. References [1] Lewis JM, Senn DR. Dental age estimation. In: Senn DR, Weems RA, editors. Manual of Forensic Odontology. Boca Raton: CRC Press Taylor & Francis Group; 2013. p. 211–55. [2] Büken B, Demir F, Büken E. Evaluation of cases sent for age estimation to forensic medicine department between 2001 and 2003 years and difficulties in forensic practice. Düzce Med J 2003;5:18–23.
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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Legal Medicine journal homepage: www.elsevier.com/locate/legalmed
Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children Nursel Akkaya a,⇑, Hümeyra Özge Yilanci b, Dinçer Göksülük c a
Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hacettepe University, 06100 Sıhhiye, Ankara, Turkey _ Izmir Dental Training Hospital, 35260 Konak, Izmir, Turkey c Department of Biostatistics, Faculty of Medicine, Hacettepe University, 06100 Sıhhiye, Ankara, Turkey b_
a r t i c l e
i n f o
Article history: Received 8 December 2014 Received in revised form 4 March 2015 Accepted 7 April 2015 Available online xxxx Keywords: Forensic science Forensic odontology Age estimation Children Adolescents A repeated measures ANOVA
a b s t r a c t The aim of this study was to evaluate applicability of five dental methods including Demirjian’s original, revised, four teeth, and alternate four teeth methods and Willems method for age estimation in a sample of Turkish children. Panoramic radiographs of 799 children (412 females, 387 males) aged between 2.20 and 15.99 years were examined by two observers. A repeated measures ANOVA was performed to compare dental methods among gender and age groups. All of the five methods overestimated the chronological age on the average. Among these, Willems method was found to be the most accurate method, which showed 0.07 and 0.15 years overestimation for males and females, respectively. It was followed by Demirjian’s four teeth methods, revised and original methods. According to the results, Willems method can be recommended for dental age estimation of Turkish children in forensic applications. Ó 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Age estimation is one of the important applications both for deceased and living people in Forensic sciences. Estimating chronological age is necessary for identification of criminal cases, victims of mass disasters and investigations of human remains in archeological studies. Age determination for living individuals is required to assess criminal responsibilities, which is crucial to decide whether accused individual or victim is below or above the age threshold for that criminal law. It is also frequently used for civil purposes and social issues such as school attendance, immigration, adoption, marriage and incorrect birth records [1,2]. Dental age estimation can be made using a number of methods, which are based on developmental features [3,4] or age-related changes in teeth, such as attrition, secondary dentin apposition, periodontosis, cementum apposition, root resorption, and root transparency [5,6]. Other approaches for age estimation include the evaluation of racemization of aspartic acid in dentine [7], telomere shortening in pulp DNA [8], the amount of radiocarbon in enamel [9]. ⇑ Corresponding author at: Hacettepe Üniversitesi Disß Hekimlig˘i Fakültesi, Ag˘ız, Disß ve Çene Radyolojisi Anabilim Dalı, 06100 Sıhhiye, Ankara, Turkey. Tel.: +90 3123052205; fax: +90 3123113741. E-mail addresses: [email protected] (N. Akkaya), ozgeerbudak@yahoo. com (H.Özge Yilanci), [email protected] (D. Göksülük).
Dental development is widely used as an indicator of chronological age in sub-adults. Dental age estimation methods and other methods including bone development, secondary sex characters, stature or weight can be applied separately or together to estimate a minor’s age [3,10]. Since dental development is less affected by environmental factors in comparison with the growth of the skeletal, somatic or sexual systems, dental age estimation methods are more reliable and accurate than the other methods, especially for children under 10 years old [1,11,12]. Several methods have been introduced for dental age estimation based on radiographic tooth development [1]. Demirjian dental development method [3,13] is one of the most commonly used techniques for age estimation in children [14]. Demirjian et al. [3,13] established four methods for dental age estimation based on eight calcification stages from calcification of the cusps to closure of the apex. The original Demirjian technique includes seven left mandibular teeth except for third molar. Disadvantage of this method is to require the existence of all seven teeth. In case of bilaterally absence of teeth, the method cannot be used. In 1976, Demirjian and Goldstein [13] presented three more methods: revised seven teeth method; four teeth method (M2, M1, PM2, PM1); and alternate four teeth method (M2, PM2, PM1, I1). In these methods, each tooth is rated based on its developmental stage, each stage is allocated a score, then sum of each score (maturity score) are converted to dental age by using standardized tables or percentile curves (50th percentile) for each gender separately.
http://dx.doi.org/10.1016/j.legalmed.2015.04.003 1344-6223/Ó 2015 Elsevier Ireland Ltd. All rights reserved.
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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N. Akkaya et al. / Legal Medicine xxx (2015) xxx–xxx
Demirjian method is based on the radiographs of French– Canadian children. The technique has been widely applied in other populations, but revealed general overestimation in most of the studies [15–26]. Several studies have pointed out that generation of new standard curves, which are specific to the population, is required [20,21,23,27,28]. Based on Demirjian scoring system, Willems et al. [29] proposed a new method that includes new tables for each sex and age score, which directly expresses in years. The adapted method was validated and resulted in more accurate dental age estimations in a Belgian Caucasian population. Previous studies generally used Demirjian’s seven teeth methods [16–26]. Also in a few researches, Demirjian’s four teeth methods were investigated [15,30,31]. In Turkish population, previous studies showed overestimation of the chronological age, which were conducted based on seven teeth methods of Demirjian [27,32–35]. Demirjian’s four teeth methods and Willems method have not been tested before in Turkish children and adolescents. Therefore, the aim of this study was to evaluate the applicability of Demirjian’s four methods; original, revised, four teeth and alternate four teeth methods, and Willems method for age estimation in a sample of Turkish children.
2. Materials and methods Investigational protocol described herein was approved by NonInterventional Clinical Researches Ethics Board at Hacettepe University. The records of the patients in the age group of 2– 16 years, who visited the Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Hacettepe University between 2011 and 2012, were reviewed. Panoramic radiographs of the patients without any obvious developmental anomalies were selected from the patients’ records. The radiographs that were unclear and that bilaterally showed teeth with gross pathology, root canal treatment, shape and position anomalies and bilateral absence of the teeth in the mandibula were excluded. The study sample comprised of digital panoramic radiographs from a total of 799 individuals (412 females, 387 males) aged 2.20–15.99 years. The chronological age of each subject was calculated by subtracting the date of the panoramic examination from the date of birth in decimal system. For all five methods (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method and D: Demirjian’s alternate four teeth method, and E: Willems method), each of the seven left permanent teeth of the mandible was assessed, and maturity scores were determined according to developmental criteria (A–H) by two observers. The right permanent teeth were evaluated when the left side was unsuitable for the evaluation. Demirjian’s sex-specific numerical scores assigned to each tooth, and they were summed up to obtain an overall maturity score, for four methods separately. These scores were subsequently converted into a dental age using published conversion tables for original method and maturity percentile curves at the 50th percentile for the other three methods. For Willems method, adapted maturity scores of seven teeth were summed up and directly obtained dental age. Before analyzing data, inter and intra-observer agreement was evaluated via Cohen’s Kappa statistic to ensure that there was no significant measurement error. To evaluate intra-observer reliability, 71 radiographs were randomly selected from the different age groups and re-examined six months after the initial scoring by two observers separately. Similarly, randomly selected 94 panoramic radiographs, seven teeth for each, were examined to evaluate inter-observer reliability. To compare dental methods among gender and age groups, a repeated measures ANOVA was performed on age differences, i.e. residuals, which is the magnitude of
difference between estimated age and chronological age. The response variable was symmetrically distributed among comparison groups, however; statistical tests rejected normality as a result of large sample size [36,37]. Previous studies showed that ANOVA is robust to moderate departures from normality and can be used when sample size is large enough [38,39]. Pairwise comparisons between methods were also provided. For each tooth, the amount of kappa was estimated above 0.7. The overall agreement, which was estimated from 658 different evaluations within 94 radiographs for each tooth, was obtained as 0.824. Intra-observer agreement values were 0.950 and 0.878. Table 1 shows that from both inter and intra-observer results, the agreement of measurements was found to be almost perfect according to the categorization of kappa statistic proposed by Fleiss [40]. Although the measuring bias was highly decreased, there still existed imbalanced structures within subgroups. As expected, the number of observations within younger subsets was extremely low. Therefore, age interval 2.99–5.99 was collected to a single group and introduced into ANOVA as <5.99.
3. Results Gender and age distributions of sample are presented in Table 2. Table 3 gives descriptive statistics for age residuals of each method independent from age groups. Willems method (E) provided the best result for both males and females. This result can be graphically seen from Fig. 1. All methods overestimated the chronological age and the amount of overestimation was slightly higher for females (Fig. 1). However, the performance of each method was found to be different for changing age groups according to ANOVA results given in Table 4. The results of repeated measures ANOVA showed that higher order interactions were significant for both within and between subject effects. Hence, we can conclude that each method gave different results for each gender and age groups (Fig. 2). For patients aged below 5.99, each method gave almost similar results for females and males whereas there were differences among methods within gender. We also demonstrated pairwise comparisons in Table 4. Since Willem’s method was found to be more accurate than Demirjian’s four methods, only the pairwise comparisons versus Willem’s method with false discovery rate (FDR) adjusted p-values were given in Table 5. For females, Willems method was significantly diverse from Demirjian’s methods at all ages. However, for males, Demirjian’s four teeth (C) and alternate four teeth methods (D) mostly gave similar results with Willem’s method (E).
Table 1 Inter/intra-observer agreement values. Tooth No.
I1 I2 C PM1 PM2 M1 M2 Total
N
94
658
Inter-observer
N
Kappa
p
0.890 0.915 0.708 0.761 0.697 0.910 0.812 0.824
<0.001
71
<0.001
497
Intra-observer Observer 1
Observer 2
Kappa
p
Kappa
p
0.965 0.862 0.940 0.926 0.982 0.977 0.930 0.950
<0.001
0.888 0.863 0.856 0.829 0.847 0.896 0.915 0.878
<0.001
<0.001
<0.001
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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N. Akkaya et al. / Legal Medicine xxx (2015) xxx–xxx Table 2 Gender and age distribution of sample. Age groups
Boys (N)
Girls (N)
Total (N)
2.20–3.99 4.00–4.99 5.00–5.99 6.00–6.99 7.00–7.99 8.00–8.99 9.00–9.99 10.00–10.99 11.00–11.99 12.00–12.99 13.00–13.99 14.00–14.99 15.00–15.99 TOTAL
5 9 7 10 19 31 43 45 41 22 39 50 66 387
3 5 3 10 11 24 36 23 22 30 52 88 105 412
8 14 10 20 30 55 79 68 63 52 91 138 171 799
4. Discussion The aim of this study was to evaluate the applicability of Demirjian’s four methods and Willems method for age estimation of Turkish children. In this study, all of the five methods were demonstrated to be both gender and age sensitive. Demirjian’s original method showed the greatest overestimation of chronological age by 0.66 and 0.52 years for females and males, respectively. Demirjian’s revised method, four teeth methods and Willems method followed it. For Willems method, differences between chronological and estimated age were 0.15 and 0.07 years for females and males, respectively. Willems method was more accurate Demirjian methods, which was consistent with previous studies [16,17,19,24,25,41–43]. Several previous studies have used original and revised Demirjian methods in different populations [15–26]. The results showed wide variations between different populations and also different groups of same population [20,44]. Considerable numbers of studies using Demirjian method reported overestimation in their population [15–28,32–35], although underestimation was also reported [45]. Studies using original and revised Demirjian methods in Turkish children from different geographic regions showed generally overestimation in dental age [27,32–35,44], as in this study. In Northern Turkish children, Tunç and Koyutürk [27] found that the mean difference between chronological and dental ages ranged from 0.36 to 1.43 years for males and from 0.50 to 1.44 years for females. In Eastern region of Turkey, Çelikog˘lu et al. [32] found that the mean difference between chronological and dental ages ranged from 0.4 to 1.3 years in males and from 0.2 to 1.9 years in females. In another Turkish study, Kırzıog˘lu and Ceyhan [34] showed that Demirjian method gave an overestimation of 0.52 years and 0.75 years for males and females, respectively. Although our results are consistent with these studies, the
Table 3 Descriptive statistics for age residuals. A
B
C
D
E
Female (n = 412)
Mean Median Std. Dev.
0.666 0.660 1.058
0.623 0.630 1.064
0.567 0.550 1.023
0.612 0.590 1.001
0.157 0.180 1.158
Male (n = 387)
Mean Median Std. Dev.
0.526 0.540 1.077
0.328 0.400 1.063
0.209 0.260 1.091
0.180 0.300 1.109
0.076 0.190 1.023
A: Demirjian’s original method. B: Demirjian’s revised method. C: Demirjian’s four teeth method. D: Demirjian’s alternate four teeth method. E: Willems method.
Fig. 1. Error bars of age residuals for each method within gender (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method D: Demirjian’s alternate four teeth method, and E: Willems method).
Table 4 Results of repeated measures ANOVA. df
SS
MS
F
p
Within subjects Method Method ⁄ gender Method ⁄ age Method ⁄ age ⁄ gender Error (within)
4 4 48 48 3092
54.574 5.439 18.892 16.05 314.1
13.64 1.360 0.394 0.334 0.102
134.3 13.38 3.874 3.292
<0.001 <0.001 <0.001 <0.001
Between subject Gender Age Gender ⁄ age Error (between)
1 12 12 773
16.655 207.507 125.644 3813.49
16.655 17.292 10.470 4.933
3.376 3.505 2.122
0.067 <0.001 0.014
minor differences in findings may be explained by variations of study design, statistical methods, sample size, age groups, age and sex distribution of the study population, and performance of observer [46]. Environmental factors such as socioeconomic status, nutrition, dietary habits and life-style may have also contributed to these differences. As mentioned by several articles the accuracy of the age estimation methods should be verified in different populations and the studies should be done to create population-specific databases [20,23,27,28,34,45]. Therefore, some authors have calculated new scores [19–21,29,47]. Willems et al. [29] firstly modified Demirjian method for the Belgian Caucasian population. In their study, Willems et al. estimated chronological age with minimal errors (a median of 0.1 years for males and 0.2 years for females), but these were not statistically significant. It was reported that Willems method provided more accurate age estimation than the Demirjian’s methods [16,17,19,24,41–43,48,49]. Our results also support this fact. Liversidge et al. [50] suggested that advancement in dental maturation may be explained by positive secular trend in growth and development. Improvement of the life conditions with better nutrition and the decline in the severity and frequency of diseases in childhood for many populations may accelerate dental development [11]. Willems et al.[29] published their revised maturity scores almost 25 years later than the study of Demirjian et al. [3,13]. Therefore, Willems et al.’s maturity scores were closer to the present time. Also in Turkish children and adolescents, positive secular changes in growth were demonstrated [51].
Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003
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Fig. 2. Age residuals of the methods for age and gender groups (A: Demirjian’s original method, B: Demirjian’s revised method, C: Demirjian’s four teeth method, D: Demirjian’s alternate four teeth method, and E: Willems method).
Table 5 Pairwise comparisons (Demirjian’s vs. Willem’s Method – FDR adjusted). Gender
AE BEà CE§ DE((
Female Male Female Male Female Male Female Male
<5.99
0.000 0.000 0.001 0.000 0.002 0.004 0.007 0.007
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
6.99
7.99
8.99
9.99
10.99
11.99
12.99
13.99
14.99
15.99
0.001 0.006 0.022 0.006 0.046 0.008 0.194* 0.071*
0.002 0.010 0.034 0.017 0.001 0.416* 0.002 0.371*
0.001 0.017 0.005 0.092* 0.000 0.416* 0.000 0.092*
0.000 0.002 0.000 0.000 0.000 0.563* 0.000 0.009
0.000 0.000 0.000 0.000 0.000 0.324* 0.000 0.226*
0.000 0.000 0.000 0.000 0.000 0.099* 0.000 0.027
0.000 0.000 0.000 0.735* 0.000 0.463* 0.000 0.767*
0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.338*
0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.123*
0.000 0.000 0.000 0.005 0.000 0.640* 0.000 0.468*
*
à §
p > 0.05. Demirjian’s original method versus Willems method. Demirjian’s revised method versus Willems method. Demirjian’s four teeth method versus Willems method. (( Demirjian’s alternate four teeth method versus Willems method.
All the methods tested in this study showed similar results for males and females whose ages below 5.99. Our findings are consistent with the previous studies [52,53] which stated that there was no difference in the timing of dental development between males and females up to 5–6 years of age. According to our results, generally, performance of each method increased slightly with age, and was better in males. The differences between chronological and estimated age showed systematic decrease between the ages of 6 and 12 years and then drastically changed for the age of 13 years in males, whereas these differences were unsteady with firstly increasing and then decreasing values for the ages from 10 and 15 years in females. This may be due to fluctuations in pubertal growth period of these ages. A mean age difference of ±1.0 year is considered accurate in forensic anthropology [47], but an acceptable range is defined ±0.5 year in some studies [31,54]. However, ideally age estimation method should arrive at an age as accurate as possible [17,43]. Among all of the five methods tested in this study, Willems method gave relatively better results than the others. Demirjian’s four teeth methods showed lower overestimation than the seven teeth
methods, as in other studies [42,54]. Moreover, Demirjian’s four teeth and alternate four teeth methods gave similar results with Willem’s method at most of ages in males. Therefore, Demirjian’s four teeth methods can be improved with further studies to estimate age in case of tooth absence for the evaluation.
5. Conclusion Based on the results of this research, it was concluded that Willems method is more suitable than Demirjian methods for dental age estimation. Therefore, this method can be used for forensic procedures in Turkish children. References [1] Lewis JM, Senn DR. Dental age estimation. In: Senn DR, Weems RA, editors. Manual of Forensic Odontology. Boca Raton: CRC Press Taylor & Francis Group; 2013. p. 211–55. [2] Büken B, Demir F, Büken E. Evaluation of cases sent for age estimation to forensic medicine department between 2001 and 2003 years and difficulties in forensic practice. Düzce Med J 2003;5:18–23.
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Please cite this article in press as: Akkaya N et al. Applicability of Demirjian’s four methods and Willems method for age estimation in a sample of Turkish children. Leg Med (2015), http://dx.doi.org/10.1016/j.legalmed.2015.04.003