The considerable incidence of extra root canals of anterior mandibular teeth that is usually missed due to lack of knowledge and scarce studies leading to improper endodontic treatment, Therefore, endodontists are in need of additional investigations to enhance the quality of the root canal treatment to avoid failure

Settings:

The data collection will be obtained from the data base 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 oral and maxillofacial radiology department for different purposes.

Variables:

•Prevalence of extra root canals in mandibular anterior teeth - Classification and prevalence of observed types -

Data Sources / Measurements:

• 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 0.2 voxel size will be reviewed.
• For proper visualization of the canals number and configuration in anterior mandibular teeth, scrolling through the three orthogonal cuts and oblique reformatted planes.
• 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.
• Vertucci classified the canal configurations of mandibular anterior teeth into four types (Vertucci, 1974) :

Type I: Single canal is present from the pulp chamber to the apex. Type II: Two separate canal leaves the pulp chamber, but join short of the apex to form one canal.

Type III: One canal leaves the pulp chamber, but it divides into two within the body of the root, the canals merge again to exist as one canal.

Type IV: Two separate and distinct canals are present from the pulp chamber to apex.

Type V: A single canal leaves the pulp chamber but divides into 2. Type VI: 2 separate canals leave the pulp chamber, join at the midpoint, and then divide again into 2 with 2 separate apical foramina.

Type VII: 1 canal leaves the pulp chamber, divides and then rejoins within the root, and finally redivides into 2 separate canals with 2 separate apical foramina.

Type VIII: 3 separate and distinct canals begin from the pulp chamber to the root apex.

• Each radiologist will evaluate the images for presence of extra root canal with a time lag of two weeks between the two reading sessions. If present, its configuration (classification) will be registered. Any disagreement will be solved by consensus between the two observers.
• If extra root canals type II , type IV or type VI is detected, then the distance between the canal orifices will be measured using built in measuring tool in the software.
• The measurements will be carried out by one observer (PY) and will be repeated 2 weeks later for intra-observer reliability assessment. Bias No source of bias.

Study Size:

Based on the Iranian paper by Haghanifar et al., 2017, the prevalence of two root canals in mandibular anterior teeth (12.1%) Using a precision of 5, a design effect set at 1 with 95% CI (confidence interval) a total sample size of 170 mandibular anterior tooth will be sufficient. The sample size was calculated by Epi info 7 software.

Inclusion criteria:

• Scans showing the anterior teeth areas.
• The teeth had to be completely developed

Exclusion criteria:

• Teeth to be examined, endodontically treated teeth.
• Teeth with crown restorations.
• Cast metal post inside the canal
• Teeth with apical lesions.
• Carious teeth
• Scans with low quality
• Dilacerated roots
• Resorbed roots

Egyptian population