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Two canals in mesiobuccal roots of maxillary molars.

The purpose of this study was to examine extracted root canal treated maxillary molars cleared for: (i) the presence of a mesiopalatal (MP) canal in both first and second molars, (ii) the extension of MP canal from the pulp to the apical area, and (iii) the incidence of two foramina in the MB root. Seventy-two extracted maxillary molars (42 first and 30 second molars) were root canal treated by graduate students. The mesiobuccal (MB) roots of these samples were rendered transparent using a clearing technique. The results demonstrated that 52.3% of first and 40% of second molars had two canals obturated in the MB root. After clearing the same roots, the presence of MP canals rose to 80.9% and 66.6%, respectively. The MP canals were root canal treated as far as the foramen in 35.2% of first and 35% of second molars. However, after making them transparent, 91.1% and 90% showed the presence of this canal to the anatomical apex. The MB roots of the root canal treated first molars showed the presence of two foramina in 47% of cases but in 88.2% after clearing. The second molars showed 50% and 70%, respectively. The differences between root canal treated teeth before and after clearing were significantly different in almost all comparisons in both first and second molars. The only exception was when the presence of two foramina was compared before and after the clearing process in second molars (McNemar test P < 0.05).