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ORIGINAL ARTICLE
Year : 2020  |  Volume : 23  |  Issue : 12  |  Page : 1753-1758

Accuracy of Estimating Chronological Age from Nolla's Method of Dental Age Estimation in a Population of Southern Saudi Arabian Children


Department of Pediatric Dentistry and Orthodontic Sciences, College of Dentistry, King Khalid University, Kingdom of Saudi Arabia

Date of Submission29-Nov-2019
Date of Acceptance26-May-2020
Date of Web Publication23-Dec-2020

Correspondence Address:
Dr. S M Yassin
Department of Pediatric Dentistry and Orthodontic Sciences, College of Dentistry, King Khalid University, Guraiger, P.O. Box: 3263, Abha-61471
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_648_19

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   Abstract 


Objectives: The aim of this study was to test the accuracy of estimating chronological age using Nolla's method of dental age assessment in a Saudi Arabian population considering sex and age group variables. Materials and Methods: This cross-sectional study involved a retrospective evaluation of 458 orthopantomographs (187 males and 271 females) of 5–11 years old healthy Saudi children. Seven permanent left mandibular teeth were assessed as per Nolla's method to record dental age. The mean difference between dental age and chronological age was calculated using a paired t-test. Correlation between chronological age and dental age was analyzed using Pearson's correlation coefficient. Results: There was a statistically significant difference (P < 0.05) between the estimated dental age and chronological age in all age groups irrespective of gender. The mean difference between estimated dental age and chronological age in males ranged from −2.68 to −6 months and −2.17 to −4.24 months in females. Pearson's correlation coefficient showed a strong positive correlation (r = 0.95 for males and r = 0.94 for females) between estimated dental age and chronological age. Conclusion: Nolla's method is suitable for estimating chronological age in Southern Saudi children, as the mean difference between estimated dental age and chronological age was within an acceptable range.

Keywords: Age estimation, dental age, Nolla's method, Saudi children


How to cite this article:
Yassin S M, M AlAlmai B A, Ali Huaylah S H, Althobati M K, A AlHamdi F M, Togoo R A. Accuracy of Estimating Chronological Age from Nolla's Method of Dental Age Estimation in a Population of Southern Saudi Arabian Children. Niger J Clin Pract 2020;23:1753-8

How to cite this URL:
Yassin S M, M AlAlmai B A, Ali Huaylah S H, Althobati M K, A AlHamdi F M, Togoo R A. Accuracy of Estimating Chronological Age from Nolla's Method of Dental Age Estimation in a Population of Southern Saudi Arabian Children. Niger J Clin Pract [serial online] 2020 [cited 2022 May 25];23:1753-8. Available from: https://www.njcponline.com/text.asp?2020/23/12/1753/304434




   Introduction Top


Estimating age in children is of paramount importance when chronological age is questionable. Chronological age is essential in many societies for school attendance, social benefits, employment, and marriage.[1] Age Assessment is critical in various civil and criminal scenes as well as in mass disaster situations. Age estimation applicability in different areas of science makes it a vital tool in identifying the age of both living and dead individuals. In the clinical scenario, age assessment in children serves a pediatric dentist to assess whether the dental maturity of a child is delayed or advanced in case of a specific disease.[2] Dental age estimation helps orthodontists to plan the timing of particular treatments in children as dental maturity varies with different forms of malocclusion.[3]

Age assessment can be done using biomarkers, secondary sexual characters, physical examinations, histological analysis, radiometric analysis, and radiographic evaluations. Most of these methods are often expensive and imprecise. However, age estimation using tooth development is a time-tested method as it is influenced mostly by genetics and less affected by environmental factors. Further, the human tooth being an enduring tissue shows negligible changes during life.[4],[5]

Although various methods of dental age assessment methods are available, age estimation using tooth mineralization is more reliable.[6] Tooth development is a continuous process displaying specific mineralization stages without being influenced by external factors.[7],[8],[9] Nolla's method uses this concept and estimates dental age based on stages of mineralization of permanent tooth that is graded on a scale of 0-10.[10] The technique devised by Nolla is widely used in teaching and clinical practice.[11] Nolla's method has been studied in different populations and is reported to be more accurate in estimating chronological age than other methods.[12],[13],[14]

In Saudi Arabia, studies have estimated chronological age using Demirjian's method, London  Atlas More Details method of human tooth development and eruption, and found it to be inaccurate.[15],[16] Ibrahim et al.[17] used Cameriere's method and derived a regression equation formula specific to the Saudi population. Although Nolla's approach is reported to estimate chronological age more accurately in other populations,[12],[13],[14] its accuracy in the Saudi population is yet to be tested. Therefore, there is a need for this study to test the accuracy of estimating chronological age using the Nolla's method of dental age assessment in a Saudi Arabian population considering variables such as sex and age groups.


   Materials and Methods Top


This cross-sectional study involved retrospective evaluation of the orthopantomographs of 5-11 years old children who attended the pediatric dental clinics at the King Khalid University College of Dentistry. Following ethical approval from the institutional review board (SRC/ETH/2016-17/034), access to the patients' data was obtained. Only Saudi children aged 5–11 years with complete case records and clear orthopantomographs were included in the study. Subjects with congenital anomalies, systemic diseases, fractured teeth, teeth with periapical lesions, malformed teeth, congenitally missing teeth, extracted permanent teeth, and history of orthodontic treatment were excluded from the study. Details regarding systemic diseases, congenital anomalies, and the history of orthodontic treatment were obtained from the case records. All orthopantomographs were acquired by digital ORTHOPANTOMOGRAPH® (OP200D Instrumentarium Dental, Finland) with a 1:1 magnification. Of the total 536 orthopantomographs, 458 fulfilled the inclusion criteria. The distribution of subjects by gender and age are presented in [Table 1].
Table 1: Distribution of study samples by age and gender

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Details of the child's age, date of birth, gender, and nationality were obtained from patients' case file records. The chronologic age was obtained by subtracting the date of birth from the radiographic date and was recorded as completed years and months. Orthopantomographs that fulfilled the inclusive criteria were coded with a numerical ID to avoid examiner bias. Thus the examiner was blinded to chronological age and gender of the study subjects. The dental age was assessed on orthopantomographs based on stages of tooth mineralization of all seven permanent mandibular teeth (excluding the third molar) on the left side. The phases of tooth mineralization were graded into ten stages, beginning from stage 1 (no sign of calcification) to stage 10 (apical end completed). If the tooth was in between two stages, an appropriate fraction of (0.2, 0.5, or 0.7) was added based on the degree of mineralization. The staged scores of mineralization for each tooth were summed up and matched with normality table for males and females formulated by Nolla[12] that provided the estimated dental age. Chronological age and estimated dental age were recorded in months to maintain a better accuracy similar to the one reported by Kurita et al.[18]

A single investigator who was trained and calibrated performed dental maturation assessments. The examiner was blinded to chronological age and gender of each subject when tooth developmental stages were assessed. Twenty radiographs were randomly selected and reexamined four weeks after the initial examination by the same investigator. A paired t-test revealed no significant difference (P = 0.18) between the two readings.

Statistical analysis

All data were entered in Microsoft Excel file and further analyzed statistically using STATA (9.2) software. Kolmogorov–Smirnov test revealed a normal distribution of data. A paired t test was applied to assess the mean difference between estimated dental age and chronological age. The level of significance was set at 5%. The difference between estimated dental age and chronologic age was considered as age error. A negative age error indicated an underestimation of age, whereas a positive age error indicated an overestimation of age. Pearson's correlation coefficients were used to evaluate the correlation between chronological age and dental age.


   Results Top


Of the total, 458 orthopantomographs selected, 187 (41%) belonged to males, and 217 (59%) belonged to female children. The difference between estimated dental age and chronologic age as per Nolla's method for different age groups are presented in [Table 2]. The mean difference between estimated dental age and chronologic age in males ranged from –2.68 to–6 months, with a maximum mean difference of −6± −2.87 months in 132 to 143 months age group, whereas the minimum difference of −2.68 ± −1.62 months in 96–107 months age group. There was a statistically significant difference (P < 0.05) between estimated dental age and chronologic age in all age groups indicating that Nolla's method underestimated chronological age among males. The relationship between estimated dental age and chronologic age among males is in [Figure 1].
Figure 1: Plot showing the relationship between dental age (DA) and chronological age (CA) in males

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Table 2: Differences between chronological age and dental age determined by Nolla's method

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The mean difference between estimated dental age and chronologic age in females ranged from −2.17 to −4.24 months, with a maximum difference of −4.24± −5.02 months in 84-95 months age group and a minimum difference of −2.17 ± −2.38 months in 60-71 months age group. There was a statistically significant difference (P < 0.05) between estimated dental age and chronologic age in all age groups among females indicating that Nolla's method underestimated chronological age among females. The mean difference between estimated dental age and chronological age was found to be more in males than in females. [Figure 2] shows the relationship between estimated dental age and chronological age in females.
Figure 2: Plot showing the relationship between dental age (DA) and chronological age (CA) in females

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Pearson's correlation coefficient was used to assess the correlation between chronological age and estimated dental age. A strong positive correlation for males (r = 0.95) and females (r = 0.94) was observed and is presented in [Table 3].
Table 3: Comparative analysis between the mean chronological age and dental age using Nolla's method for males and females

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   Discussion Top


Dental age is considered to be more pertinent with chronological age than other growth development markers. Dental age assessment based on tooth mineralization is said to be more reliable than gingival emergence or eruption, the reason being that tooth mineralization is primarily controlled by genes and less influenced by external factors. Among various dental age assessment methods, the radiographic method has been found to be more advantageous as it is simple, economical, non-mutilating, and noninvasive.[19],[20] In particular, panoramic radiographs are widely preferred to assess dental maturity as it provides a distortion-free single image of the entire dentition.

Though Demirjian's method of dental age assessment is often used, Nolla's method is reported to be more accurate in different populations.[13],[21] This method added two more degrees of mineralization of crown than the Demirjian method, in an attempt to make it more precise in assessing dental age.[22] However, the literature search revealed, none of the studies have tested the accuracy of Nolla's method of dental age assessment in the Saudi population. Thus, this study aimed to assess the accuracy of estimating chronological age using Nolla's method of dental age assessment in a Saudi Arabian population.

Accuracy and precision are two essential factors to be considered during the dental age assessment in estimating chronological age. Nolla's method has provided mixed results in various populations. When tested on Turkish children, Nolla's method reported underestimation of chronological age, with the mean age error of –0.3 years.[23] However, it overestimated chronological age, on 5–16 years old Malaysian children with a mean age error of 0.54 years.[24] In contrast to other studies, Nolla's method was found to be suitable in estimating chronological age for a group of Brazilian children with due care considering the growth spurt commencing around 11 and 12 years.[13]

In our study, though there was a strong positive correlation between chronological age and estimated dental age, Nolla's method underestimated chronological age in all age groups and both genders. The age difference was found to be –2.68 months to –6 months in males and –2.17 months to –4.24 months in females. Maber et al.[25] reported similar results of underestimation of chronological age by –0.87 years for males and –1.18 years for females in their study on 3–16.99 years old children of Bangladesh, and British Caucasian ethnic origin. Bolanos et al.[10] concluded that Nolla's method predicted chronological age more accurately for Spanish males and females below 10 years age group, similar to the findings of our study. The different results in various populations can be attributed to genetic variations, ethnicity, climate, nutrition, sample structure, and biological variation of individual children.[26] Thus population-specific dataset needs to be formulated to ensure sufficient accuracy in age estimation.

Gender wise difference has been reported and needs to be considered. In this study, the chronological age was underestimated for both genders. However, the underestimation observed was lesser for females than males indicating an advanced dental maturity in females. The mean difference between estimated dental age and chronological age was –3.66 months in males and –3.29 months in females. Besides, there was a statistically significant difference between males and females in all age groups. Similar findings were reported by Nur et al.[12] in their validation study using Nolla's and Demirjian's method in Turkish children, reported the mean difference between chronological age and dental age in females was 0.15–1.24 years, whereas it was 0.27–1.60 years in males. Aisha et al.[27] in their study on 8–17 years old Pakistani orthodontic patients using Nolla's method, observed an advanced dental maturity of 0.21 ± 1.64 years in females, whereas a delayed dental maturity of –1.00 ± 1.54 years in males. Previous studies have reported that both tooth formation, as well as tooth emergence, is more advanced in females similar to other maturity markers such as sexual maturity, height, and skeletal development. Thus because of their faster maturation, females might show less variation of estimated dental age to chronological age than males.[28],[29],[30]

The probable reason for the underestimation of chronological age by Nolla's method could be due to the increased number of stages. The method enables the observer to choose between the ten stages with additional three interstage options for each stage, accounting for a total of 40 stages. Expanding the number of stages is reported to decrease the exactness and accuracy of the method.[31],[32]

Moreover, tooth formation stages are not similarly dispersed during their development and are not of equal term. Information on the exact timing of crown/root fraction formations is minimal till date. The variation between ethnic groups is a vital factor and is supported by recent findings by differences in tooth formation. The other reason could be the genetic and environmental influences affecting the biological growth and dental development among populations. Hence chances of misrepresentation of health status and growth data can occur if the standard used for one population is applied to the other as seen in this study.[26],[33]

Chaillet et al.[34] considered a mean difference of ±1 year between chronological age and dental age as accurate in forensic anthropology, whereas McKenna et al.[35] commended ±0.5 years to be more acceptable. An age estimation method is accurate if it predicts the chronological age as close as possible. In this study, the mean difference between chronological age and dental age in male subjects was less than six months in all age groups except those in the age group of 132 to 143 months. Thus, Nolla's approach can be used for age estimation in Southern Saudi males aged between 60 and 131 months. Nevertheless, in female subjects, the mean difference between chronological age and dental age was less than six months in all age groups studied, suggesting that Nolla's method can serve as a reliable tool for estimating chronological age in Southern Saudi females.

The study had limitations such as including a limited number of age groups and a collection of samples from a single site. Hence, the results of this study cannot be generalized to the Saudi population. Further studies with larger samples and a more extensive age range from all regions of Saudi Arabia need to be carried out with greater emphasis on nutrition, gender, and age. This research also provides more scope for comparing with other age estimation methods in the Saudi population.


   Conclusion Top


Nolla's method can be used for chronological age estimation in Saudi children with due considerations of the limitations mentioned above. However, for a more precise estimate, we recommend creating population specific standards with larger samples.

Financial support and sponsorship

This research work was funded by the Collaborative Centre of Creative and Maxillofacial Research and Treatment modalities, College of Dentistry, King Khalid University (PROJECT NUMBER: MRMC-01-019).

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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