Background: The second mesiobuccal (MB2) canal in the maxillary first molar is the most commonly missed endodontic canal, and recent evidence suggests the use of CBCT-based bilateral symmetry for prediction of its anatomy. There are no data on the Iraqi populations, and no study has investigated whether configuration symmetry is associated with inter-orifice distance symmetry. 
Objective: This study aimed at investigating the bilateral symmetry of the MB2 presence and configuration, and its association with the inter-orifice distance symmetry, in the Iraqi population.
Methods: A retrospective CBCT study was conducted on 40 subjects (80 maxillary first molars; 20 females, 20 males), classified as either MB2 absent, Fused, or Separate. The bilateral symmetry was assessed using Cohen's Kappa and McNemar's tests. The absolute difference of inter-orifice distance between the configuration-similar and dissimilar pairs was measured and the correlation between the right and left sides was calculated.
Results: MB2 was present in 87.5% of molars (92.5% right, 82.5% left). Concordance of presence was moderate (κ = 0.55, 90.0% agreement) while concordance of configuration was moderate (κ = 0.45, 72.7% agreement, n = 33). The absolute difference of intra-patient distance measurements between concordant and discordant pairs was not significantly different (0.49 ± 0.43 mm vs 0.49 ± 0.39 mm; P = 0.935), while there was no correlation between right–left distances (r = 0.15, P = 0.409).
Conclusion: Moderate bilateral concordance of MB2 presence and configuration in this Iraqi-Iranian population was seen to be lower than what had been reported elsewhere and was without any inter-orifice distance symmetry. Bilateral anatomy can help in clinical suspicions but cannot substitute for independent examination of each individual tooth.