What percentage of maxillary first molars have two canals in the MB root?
A. Maxillary molars have a mesiobuccal (MB) root that usually contains two root canal systems which oftentimes communicate anatomically along their respective lengths. Histological research has shown the MB root holds a second MB2 canal approaching 100% of the time. Clinically, the MB2 root canal system can be identified and treated in approximately 75% of the cases without a microscope and in over 90% of the cases with a microscope. The MB2 system lies mesial to an imaginary line between the MB1 and palatal orifices. Access cavities need to be expanded laterally at the expense of the Mesial Marginal Ridge (MMR), rather than chasing deep at the expense of the pulpal floor, to facilitate identification and treatment. The maxillary 2nd molar should be suspected of having a second canal in the MB root until proven otherwise. Importantly, research shows that the MB1 and MB2 terminate separately in two or more foramina about 60% of the time.
