Retreatment due to missed MB2 (again…)
Jon Richards DDS MS
Upper first molars are the most commonly retreated tooth in the mouth. This is due to the very high likelihood of a difficult to locate fourth canal, commonly called the MB2.
It is a miconception that this canal is present only 30-50% of the time. As a general rule, it should be considered present until searches for it are unfruitful (and even then be considered present, but not found!)
This includes clinically (under the maginfication and illumination of the dental operatine microscope), and radiographically. 3D CBCT scans can be very helpful in determining the location of this often elusive canal. Often times it can be found splitting deep from the MB1, or even as a branch exiting at the level of the palatal canal orifice. We find it is present in some form in roughly 85% of the cases we treat.
In this case, tooth #14 was treatment planned for a new crown. The referring dentist was astute and tooth a pre-treatment radiograph which revealed the presence of a periapical finding. In addition, the previous endodontic therapy appeared to have inadequately address the canal spaces in multiple roots.
After the core was placed, the untreated MB2 canal was located. The curvature of the MB root had resulted in a mid-root ledge associated with MB1. This was bypassed. All previous restrorative and obturation materials were removed, and patency was established in every canal.
The patient reported mild symptoms (slight biting tenderness) for a few days following the first appointment, which resolved with over-the-counter ibuprofen.
Following obturation with warm gutta percha and sealer, a bonded amalgam core was placed.