Assessment of Reliability of Demirjian Formula for Age Estimation Using Mandibular Third Molar in a Sample of Egyptian Population Using CBT: a Cross-sectional Study

this is a cross-sectional study.

The data collection will be obtained from the database available at the Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Cairo University. CBCT images will be obtained from Egyptian patients who were referred to the CBCT unit in the oral and maxillofacial radiology departments for different purposes.

• Retrospective Data Analysis will be performed after the CBCT images are pooled from the computer database.
• Exposure parameters of the scans will vary depending on patients' sizes (according to the manufacturer's recommendations).
• Images with 0.4 voxel size or less will be reviewed.
• Evaluation of the calcification of third molar will be done using the reformatted panoramic view of CBCT scans and will be compared with the Demirjian chart (8 stage grading scheme for third molar).
• The third molars from the lower left quadrants will be assessed and categorized into their respective developmental stages given by Demirjian.
• CBCT images will be interpreted by two oral and maxillofacial radiologists (with different experiences) independently; blinded from demographic data of the patients and from the results of each other.
• Each radiologist will evaluate the images for proper determination of the third molar calcification stage and to decide the dental age of the patient according the chart provided by demirjian et al.
• The calcification stage determination will be carried out by one observer and will be repeated later for intra-observer reliability assessment.
• Any disagreement will be solved by consensus between the two observers.
• The chronological age recorded based on his/her date of birth will be correlated with developmental stages of third molar.

The two oral and maxillofacial radiologists interpreting the scans will be blinded from demographic data of the patients and from the results of each other.

A power analysis was designed to have adequate power to apply a statistical test of the null hypothesis that there is no difference would be found between chronological age and developmental age of third molar according to modified Demirjian chart. By adopting an alpha level of (0.05) a beta of (0.2) i.e. power=80% and an effect size (d) of (0.26) calculated based on the results of Mohammed, Rezwana Begum, et al. ; the predicted sample size (n) was a total of (117) cases. Sample size calculation was performed using G*Power version 3.1.9.7 Numerical data will be explored for normality by checking the data distribution, calculating the mean and median values and using Kolmogorov-Smirnov and Shapiro-Wilk tests. If the data was found to be normally distributed, it will be presented as mean and standard deviation values. If the assumption of normality was found to be violated, the data will be presented as median and range values.