The study design of this study research was passed on Yang et al design .
This study was approved by the Medical Ethics Committee of the Faculty of Dental Medicine, Al Azhar University, Assuit, which granted approval for the research with number (AUAREC20200315-11). The procedures were carried out in conformity with applicable laws and regulations. All patients provided signed consent forms after being given written information.
Patients required radiographic examination of CBCT as part of their dental treatment. The images were taken as part of the routine examination, diagnosis, and treatment planning of patients that included those suffering facial trauma who required oral surgery, orthodontic treatment or who needed implant treatment. With the informed consent of the patients.
CBCT was used to scan the mandibular region of the patient to obtain a continuous image of the mandibular 1st molar and its periodontal tissue.
CBCT scan of 1650 patients were observed between January 2021 to February 2022 were collected using the CBCT imaging system from the database of the department of oral radiology, faculty of dental medicine, Al-Azhar university - Assiut branch. All images were included in the study and further analysis according to the following inclusion criteria:
- Age between 20 and 60 years.
- Lower 1st molars that had not been received root canal treatment.
- Lower 1st molars without periapical disease.
- Lower 1st molars exhibit absence of coronal or post and core restorations, which may obscure the imaging study.
- Cases where physiological or pathological processes compromised the anatomy, and the original root canal morphology was not clear.
- Images with missing all mandibular molars.
CBCT images were acquired using Orthophos S 3D extraoral imaging system (Dentsply Sirona) A scout view was acquired, and adjustments were made to ensure that all patients were correctly adjusted in the scanner according to light beam before acquisition. the Feld-Of-View size (FOV) of 8×8 cm, a peak voltage of 90 kV, a beam current of 16 mA and an exposure time of 14.s for a full arch. The voxel size was 160 μm×160 μm, and the minimum layer thickness was 0.16 mm. The detector resolution was 1024×1024 pixels, and the pixel size was 127 μm×127 μm.
After acquisition, data were exported and transferred to Sidexis software (Sirona, DICOM viewer software, version 4.0.2, Germany) Serial axial, coronal, and sagittal CBCT images were thoroughly examined from the pulp orifice to the apex. All the images were assessed separately by two endodontists. In cases of disagreement, these two endodontists discussed the data until a consensus was reached. An oral radiologist provided guidance when necessary. CBCT was used to scan the mandibular region of the patient to obtain a continuous image of the mandibular 1st molar and its periodontal tissue.
Variables to be analysed in this study:
1) Incidence frequency of the MMCs present in lower 1st molars (Figure 1).
2) Middle Mesial Canals classification (Figure 2) according to the classification of Pomeranz et al. :
a) Confluent either with the mesio buccal canal or with the mesio lingual canal, b) Independent, and c) Fin type (no separate orifice).
3) Frequency of occurrence of MM canals according to age.
Categorical data were presented as frequencies (n) and percentages (%) and were analyzed utilizing Fisher’s exact test. Numerical data were explored for normality by checking the data distribution, calculating the mean and median values, and using Kolmogorov-Smirnov and Shapiro-Wilk tests. Data showed parametric distribution, so they were presented as mean and standard deviation (SD) values and were analyzed using one-way ANOVA test. The significance level was set at p ≤0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.0.3 for windows ® Core Team (2020).