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Table of Contents   
ORIGINAL RESEARCH  
Year : 2019  |  Volume : 30  |  Issue : 3  |  Page : 352-357
Accuracy of Demirjian's and Indian-specific formulae in age estimation using eight-teeth method in Kanyakumari population


1 Department of Oral Pathology, Malabar Dental College and Research Centre, Edappal, Malappuram, Kerala, India
2 Department of Oral Pathology, Sree Mookambika Institute of Dental Sciences, Kulasekharam, Kanyakumari, Tamil Nadu, India

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Date of Web Publication9-Aug-2019
 

   Abstract 

Background: Most of the scientific formulae for age estimation in forensic odontology were tested among western population and hence cannot be applied to the Indian population consistently. Therefore, it was in this context that Dr. Ashith B. Acharya had carried out a study using the modified Demirjian's method in Indian population and found out that the study gave inferior results for age estimation. So he developed Indian-specific regression analysis and worked out a formula. Aim: This study was done to validate age using Demirjian's eight-teeth method and to compare the effectiveness of Demirjian's formula and Indian-specific formula in Kanyakumari population. Material and Methods: Digital orthopantomographs of 150 patients fulfilling the inclusion and exclusion criteria in the age group of 8–24 years were used in the study. The third quadrant in the radiograph was assessed visually from mandibular central incisor to the third molar using Demirjian's modified criteria chart. Calculation of the dental age was done using Demirjian's formula and Ashith B. Acharya's Indian-specific formula. The difference between chronological age and dental age was calculated, and the mean absolute error (MAE) was obtained. Results: The MAE was 0.20 years for the whole of Kanyakumari population, and for males it was 0.10 years and for females 0.29 years with Indian-specific formula, whereas the MAE was 2.66, 1.86, and 3.51 years, respectively, for the whole of Kanyakumari population, males, and females using Demirjian's formula. Conclusion: The observations from this study suggest that the MAE was less between chronological age and estimated dental age which was calculated using Indian-specific formula, compared with the values obtained using Demirjian's formula. Thereby we conclude that Indian-specific formula is more reliable in age estimation of Kanyakumari population.

Keywords: Age estimation, Demirjian's method, mean absolute error

How to cite this article:
Akhil S, Joseph T I, Girish K L, Sathyan P. Accuracy of Demirjian's and Indian-specific formulae in age estimation using eight-teeth method in Kanyakumari population. Indian J Dent Res 2019;30:352-7

How to cite this URL:
Akhil S, Joseph T I, Girish K L, Sathyan P. Accuracy of Demirjian's and Indian-specific formulae in age estimation using eight-teeth method in Kanyakumari population. Indian J Dent Res [serial online] 2019 [cited 2019 Aug 24];30:352-7. Available from: http://www.ijdr.in/text.asp?2019/30/3/352/264132

   Introduction Top


Age estimation forms one of the most important subdisciplines of forensic sciences and is of paramount importance in medicolegal issues. It plays an important role in several dental spheres. In forensic dentistry, there is always a need to determine the age of unidentified skeletons or individuals who have no record/documentation of their chronological age.[1],[2],[3] Various biological age estimation methods have been developed and they were based on skeletal, morphological, secondary sexual character, and dental findings. The aim of determining age is to give the forensic odontologist an accurate age range within a biological profile. To provide the greatest possible value, the method used should have the lowest achievable standard deviation (SD).[4]

In the present scenario, most of the age estimation techniques are invasive, requiring lengthy processing time, use of expensive instruments, and the services of an expert pathologist to deduce the age of a person. But the biggest pitfall had been the lack of the usefulness of these methods in vivo. It is in this case that the branch of radiology comes handy as it gives an insight into the developmental stages of the teeth, which provides a baseline data for age estimation in children and adolescents.[5]

There are various radiographic methods available for age estimation. But the most commonly used one is the Demirjian's method which is based on French-Canadian population. This is mainly because of the simplicity of the method, as well as radiographic and schematic illustrations of the tooth development and accompanying description, which the original and the subsequent works provided. This method uses orthopantomographs to estimate the extent of mineralized dental tissues and the shape of the chamber of seven left permanent lower teeth. This method classified the development of teeth into eight stages and arrived at an age estimation method.[4],[6]

The original method used only the seven mandibular teeth on the left side and assigned a gender-specific maturity score to each tooth. The scores were summed up and compared with the centile charts to arrive at the estimated age.[4] The original Demirjian's method excluded the third molar because of variability in its development, eruption, and anatomy. But the third molar provides the only reliable radiological parameter for age estimation in the age group of 16–23 years. Chaillet and Demirjian in 2004 proposed changes to the original method by incorporating the third molar and developed a new maturity score based on a French population.[7],[8],[9]

Most of the scientific formulae for age estimation in forensic odontology were tested among the western population and hence cannot be applied to the Indian population consistently. Hence, it was in this context that Dr. Ashith Acharya had carried out a study using the modified Demirjian's method in the Indian population and found out that the study gave inferior results for age estimation. So he developed Indian-specific regression analysis and worked out a formula.[10],[11] This study was done to validate age using Demirjian's eight-teeth method and to compare the effectiveness of Demirjian's formula and Dr. Ashith Acharya's Indian-specific formula in Kanyakumari population.


   Materials and Methods Top


The study sample consisted of digital orthopantomographs of patients, which were taken from the archives of Departments of Oral Medicine and Radiology and Orthodontics. The sample size was calculated to be 132 and approximated to 150 with the power of 80%, and data for the sample size calculation were taken from the study conducted by Sarkar SS et al. in 2013. The study group comprised 150 digital panoramic radiographs of patients within the age group of 8–24 years, equally distributed between the sexes and which fulfilled the inclusion and exclusion criteria [Table 1].
Table 1: Exclusion criteria

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All the radiographs taken for routine diagnostic purpose and orthodontic treatment were considered. The subjects selected for the study were contacted to verify chronological age, and informed consent was obtained. In this study, the third quadrant in the radiograph was assessed visually from 31 to 38 using Demirjian's modified criteria chart, which included 10 developmental stages instead of 8. The stages were then entered into a separate scoring proforma following which the sex-specific maturity score for each tooth was entered depending on the scoring grades developed by Demirjian. Calculation of dental age using the mandibular third quadrant teeth was carried out separately using Demirjian's [9] and Ashith B. Acharya's Indian-specific formulae.[11] The value so obtained was designated as the calculated dental age.

The difference between the chronological age and dental age was calculated and the mean absolute error (MAE) was obtained. MAE is considered as a standard measure to estimate the effectiveness of the methods in age estimation studies. The accuracy of age prediction is usually represented by the MAE, which is calculated as the difference between the calculated age and the actual age at the time of exposure. The number of values that fell in the error group of <±1 year, within 1.1–2 years, and >±2 years was noted. Error of <±1 year is considered a good result and error rate of >±2 years is considered as inaccurate.[11],[12]

Statistical analysis

The mean and SD were calculated using the descriptive statistics. Data were analyzed by Statistical Package for Social Services (SPSS 20.0) trial version. Normality of the data was assessed using Kolmogorov–Smirnov test. Data were found to be normally distributed, and hence, “paired-t” test was used to find statistical significance. The limit of statistical significance was set as 0.05 (P < 0.05).


   Results Top


The dental age of each individual was calculated by evaluating the panoramic radiographs using Demirjian's eight-teeth method, Demirjian's formula, and Indian-specific formula developed by Ashith B. Acharya. Accordingly, the mean dental age of males was 15.61 years and that of females was 17.47 years; 16.54 years was the calculated mean dental age for the total sample size according to Indian-specific formula; whereas using Demirjian's method, the mean dental age of males, females, and that of total sample was 13.85,14.25, and 14.08 years, respectively. The interquartile range of chronological age for study sample was 6, whereas it was 5 and 5.63 for dental age calculated by Demirjian's method and Indian-specific formula, respectively.

The effectiveness of age estimation by the said criteria, Demirjian's method, and Indian-specific formula was compared in terms of MAE between estimated and actual age, and the number of age estimates that were either <±1, 1.1–2, and >±2 years, respectively. The MAE which was calculated by finding out the difference between chronological age and calculated dental age was 0.20 years for the whole of Kanyakumari population. The MAE for males was 0.10 years and that for females was 0.29 years using Indian-specific formula, and using Demirjian's formula the MAE was 1.86 years for males, 3.51 years for females, and 2.66 years for the whole of Kanyakumari population. The number of age estimates that were either <±1, 1.1–2, and >±2 years were calculated which gave the error rate and accuracy of the results [Table 2].
Table 2: Distribution of percentage (number) of samples under different error rates

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All the values calculated were expressed in terms of mean ± SD. The results obtained were tabulated and subjected to statistical analysis. Statistical analysis did not yield any significant statistical variation (p > 0.05) using Indian-specific formula in all the samples. When Demirjian's formula results were subjected to statistical analysis, there was a significant difference (P < 0.05) between calculated age and chronological age in all samples [Table 3].
Table 3: Statistical analysis between the two formulae

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   Discussion Top


Forensic odontologists often face the problem of determining the age of unknown bodies and also living persons. Tooth is considered as a dependable body part for forensic age estimation since environmental factors have little influence on it.[13] Various methods for age estimation using teeth were formulated through the years. Among the different methods used for age determination in individuals, the radiological method has got a number of advantages over histological, biochemical, and genetic methods.[14]

The original Demirjian's method using the seven mandibular teeth had a high accuracy but poor reliability.[5] Subsequently, Chaillet and Demirjian modified their method to incorporate the third molar and developed a new maturity score based on a French population.[9] Ashith B. Acharya in his study used the eight-teeth method in 547 Indians (199 males and 348 females) age 7–25 years discussed the effectiveness of original formula and Indian-specific formula. The study showed that the cubic functions by Chaillet and Demirjian provided the best fit for French population and same cubic functions misclassified the Indian sample. Regression analysis was performed considering the variations for the Indian sample to derive Indian-specific formula.[11]

In this study, the dental age was evaluated using modified Demirjian's eight-teeth method, Demirjian's formula, and Indian-specific formula developed by Ashith B. Acharya using 150 digital orthopantomographs [Figure 1] and [Figure 2]. The sample size was equally distributed among both males and females. Accordingly, using Demirjian's formula, the mean dental age of males, females, and of the total sample size was 13.84, 14.24, and 14.04 years, respectively. Using Indian-specific formula, the mean dental age of males was 15.61 years and that of females was 17.47 years; 16.54 years was the calculated mean dental age for the total sample size [Graph 1] and [Graph 2].
Figure 1: Orthopantomograph of an 11-year-old male

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Figure 2: Orthopantomograph of a 17-year-old female

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The effectiveness of age estimation by Demirjian's formula and Indian-specific formula was compared in terms of MAE between estimated and actual age.[11] The study revealed that the MAE in Demirjian's formula which was calculated by finding out the difference between chronological age and calculated dental age was 2.66 years for the whole of study population which was greater than studies conducted by Acharya AB (1.29 years),[11] Sarkar S et al. (1.57 years),[15] and Mohammed RB et al. (1.61 years).[16] The MAE calculated by Indian-specific formula was found to be 0.20 years for the whole of study population which was much lesser than studies conducted by Kumar VJ et al. (1.18 years),[5] Acharya AB (0.87 years),[11] Sarkar S et al. (0.94 years),[15] and Mohammed RB et al. (0.53 years).[16] The values in our study were much closer to the actual age compared with the studies done by various other authors, which could be as a result of careful selection of sample and only one-fifth of the sample size above the age group of 20 years where maximum variations are usually seen.

In this study, the MAE which was found out using Demirjian's formula for males was 1.86 years which was lesser than the MAE of the whole population of the same study and greater than studies conducted by various other authors like Acharya AB (0.94 years),[11] Kiran CS et al. (0.89 years),[17] whereas studies done by Sarkar S et al. (1.63 years)[15] and Mohammed RB et al. (1.66 years)[16] showed an MAE equal to our study. Using Indian-specific formulae, the MAE for males was 0.10 years which was much lesser than the MAE of the whole population of the same study and studies conducted by various other authors like Kumar VJ et al. (1.2 years),[5] Acharya AB (0.70 years),[11] Kiran CS et al. (1.72 years),[17] and Tandon et al. (0.85 years).[18] The MAE for males in our study was equal to that of studies done by Sarkar S et al. (0.10 years)[15] and Mohammed RB et al. (0.21 years).[16] Thus, age estimation of males using Indian-specific formula in our study was more accurate than that of the whole population in the same study and the studies by various authors.

Using Demirjian's formula, the MAE for females was found to be 3.51 years. When compared, it was more than the MAE in males and that of the whole population of the same study using Demirjian's method. The MAE of females of our study was much more than the studies conducted by various other authors like Acharya AB (1.55 years),[11] Sarkar S et al. (1.54 years),[15] Mohammed RB et al. (1.55 years),[16] and Kiran CS et al. (0.83 years).[17] This was because more number of samples was present in the age group above 20 years in females where the maximum number of variations is present.

The MAE for females in our study using Indian-specific formula was 0.29 years and it was much less than the studies conducted by various other authors like Kumar VJ et al. (1.05 years),[5] Acharya AB (0.99 years),[11] Sarkar S et al. (0.94 years),[15] Mohammed RB et al. (0.85 years),[16] Kiran CS et al. (1.91 years),[17] and Tandon et al. (0.87 years).[18]

The MAE is a quantity used to measure how close predictions are to the eventual outcomes. It is the mean error irrespective of positive or negative sign.[17] The MAE has been advocated by a number of authors as a measure to quantify methods' accuracy. Errors of <±1 year have been considered as “good results,” and errors >±2 years have been designated as “inaccurate.”[11] Accordingly, the age estimates that were either <±1, 1.1–2, and >±2 years were calculated and this gave the error rate and accuracy of the results. The MAE was <±1 years in 37.33% of males, 14.67% of females, and 26% of the whole population using Demirjian's formula; whereas using Indian-specific formulae, 52% of males, 52% of females, and 52% of whole population had an MAE <±1 year. About 18% of males, 13.3% of females, and 18.7% of the whole sample size had MAE in the range of 1.1–2 years, respectively, using Demirjian's formula, whereas 28% of males, 30.7% of females, and 29.3% of whole sample size were found in the same age range using Indian-specific formula [Graph 3] and [Graph 4].



The error rate of >±2 years was established in 38.7% of males, 72% of females, and 55.3% of the whole population using Demirjian's formula. About 20% of males, 17.3% of females, and 18.7% of the whole population had error rate of >±2 years using Indian-specific formula. The error rate of <±1 and 1.1–2 years in our study was in accordance to studies conducted by Ashith B. Acharya and Kumar VJ et al. The error rate of >±2 years was higher in our study than that of Acharya (7%)[11] and Kumar VJ et al (10.75%)[8] using both formulae. The higher error rate of >±2 years in our study could be probably due to the higher sample size in age group of above 20 years, where there is always an underestimation of age by 7.5 and 7.85 years by Demirjian's formula and 4.5 and 3.25 years by Indian-specific formula, respectively, for males and females. The results clearly show that Indian-specific formula had more number of values under error rate of <±1 year when compared with Demirjian's formula making it more reliable. This suggests that the variation is not significant and that Demirjian's eight-teeth method along with Ashith B. Acharya's Indian-specific formula is suitable for estimation of age in Kanyakumari population.


   Conclusion Top


In conclusion, it is proved that age estimation using Demirjian's formula resulted in an inferior age prediction of Kanyakumari population, whereas there was very less difference between estimated dental age and chronological age calculated using Indian-specific formula. Age estimation in males was more accurate than that of the whole population using Indian-specific formula. Further studies with larger sample size are required to validate whether Indian-specific formula can be used to find out age in different populations in India since India is a vast land with distinct ethnic diversity.

Acknowledgement

The authors thank the Departments of Oral Medicine and Orthodontics, Sree Mookambika Institute of Dental Sciences, Kulasekharam.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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Correspondence Address:
Dr. K L Girish
Department of Oral Pathology, Sree Mookambika Institute of Dental Sciences, Kulasekharam - 629 161, Kanyakumari, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_768_17

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