Orthodontic Journal of Nepal, Vol. 11 No. 1 January - June 2021 40 Research Article Dr. Sumita Upadhyay 1 , Dr. Sijan Poudyal 2 , Dr. Prashant Khatiwada 3 , Dr. Bibardha Khanal 4 , Dr. Rasna Shrestha 5 1 Associate Professor, 4, 5 Lecturer, Dept. of Pediatric and Preventive Dentistry, Kathmandu University School of Medical Sciences, Dhulikhel Hospital, Dhulikhel, Kavre, Nepal. 2 Associate Professor, Dept. of Community Dentistry, KIST Medical College and Teaching Hospital, Kathmandu, Nepal. 3 Assistant Professor, Dept. of Radiology, National Academy of Medical Sciences, Bir Hospital, Kathmandu, Nepal. Corresponding author: Dr. Sumita Upadhyay; Email: drsumipedo@gmail.com Introduction: Dental age estimation using orthopantomogram is very useful in pediatric dentistry, orthodontics in clinical diagnosis and treatment planning and also has forensic application. Demirjian method is widely used for age estimation and Willems method has been suggested to be accurate than Demirjian in various populations. To estimate the dental age of children in a specifc population of Nepal by Demirjian and Willems method, compare them with the chronological age and assess their applicability. Materials and Method: Digital orthopantomograms of 5 to 14 years of children were used to estimate the dental age by Demirjian’s 7- teeth method and Willems method. Descriptive statistics was used and mean with standard deviation was calculated for gender and age of the samples. Paired t-test was used for comparison of chronological age with dental age. P < 0.05 was considered as statistically signifcant.Pearson correlation was used to assess the correlation between chronological and dental age in both the genders. Result: By Demirjian method, there was an underestimation of 0.276 years in males and 0.194 in females and by Willems method, 0.652 in males and 0.847 in females which were statistically signifcant. There was an underestimation of dental age in all the age groups except in the age group of 5,7 and 14 for Demirjian age which was statistically nonsignifcant. Pearson correlation demonstrated strong positive correlation between chronological age and dental age. Conclusion: The underestimation of dental age was more by Willems method as compared to Demirjian method. There was a strong positive relationship between chronological age and dental age in both the genders. Demirjian’s 7- teeth method was more applicable as compared to Willems method when tested in selected Nepalese children population. KEYWORDS: Age estimation, Dental age, Demirjian method, Nepalese children, Willems method INTRODUCTION Dental age estimation has signifcance in clinical practice in pediatric dentistry, orthodontics, research in biological growth and development as well as in forensic odontology. Estimation of dental age in children can simply be done on the basis of time of teeth emergence but tooth calcifcation has been found to be a defnitive measure of dental maturity as it is not infuenced by local factors such as the loss of primary teeth, crowding, malnutrition, caries, ankylosis. 1-3 There are various methods for estimation of dental age in children based on permanent tooth formation. 1, 3, 4 -7 The most widely used method is Demirjian method. This method was frst done in French Canadian population. 1 Several researches using this method in different population has either overestimated 8-11 or underestimated dental development. 12, 13 Estimation of Dental Age by Demirjian and Willems Method in a Tertiary Care Hospital of Nepal ABSTRACT