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
Condition: Estimated Age Calculated Based on Modified Demirjian Method Using Mandibular Left Third Molar
Study type: Observational

Summary: 
      Aim: To assess the reliability of age estimation in Egyptian adolescents and young adults
      using mandibular third molar stages of calcification, based on the Demirjian method, on CBCT
      scans.

      Methodology: 145 CBCT scans for the mandibular left posterior region were collected from the
      database of the maxillofacial radiology clinic of the faculty of dentistry at Cairo
      University. The scans were then analyzed using Planmeca Romexis software viewer version
      4.6.2.R. The mandibular left 3rd molars were evaluated to determine the calcification stage
      of each of them based on the modified Demirjian method. According to the assigned
      calcification stage, the dental age was determined, and then the mean ± SD for each
      calcification stage was calculated and compared to the chronological age in terms of mean
      difference and mean absolute error. The correlation between the calculation stage and
      chronological age was analyzed, and the probability for an individual to be 18 years of age
      or older in each stage was calculated.
    

Detailed description: 
      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.

      Categorical data will be represented as frequency (n) and percentage (%). Categorical data
      will be represented as frequency (n) and percentage (%) and will be analyzed using chi square
      test. 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 and Paired t-test will be used for the analysis. If the assumption of
      normality was found to be violated; the data will be presented as median and range values and
      will be analyzed using Wilcoxon signed-rank test. The significance level will be set at p
      ≤0.05 for all tests. Statistical analysis will be performed with IBM® SPSS® Statistics
      Version 26 for Windows.
    

Intervention name(s): CBCT scan
Intervention type(s): Other
Intervention description(s): analysis of the CBCT scan to assign a calcification stage to the subject's lower left third molar and accordingly calculate the estimated age of each subject
Observational model: Ecologic or Community
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        CBCT scans from the database available at the department of Oral and Maxillofacial
        Radiology, Faculty of Dentistry, Cairo University.
      
Keywords: Demirjian; CBCT; age estimation