Here, we'll use multiple images to explain the thought process behind our treatment protocol. Fig. 1 Fig. 3 A 36-year-old patient presents with a chief complaint of needing a root canal in his upper tooth. The patient had a previous formocresol pulpotomy to address pain and discomfort; upon examination, it was noted that the tooth had a severely curved mesial buccal root in addition to the previous pulpotomy. Note: The presence of a prior pulp cap can complicate the procedure if there is any coronal calcification associated with the previous pulp therapy. This is something to be mindful of as one begins the procedure. Following access through the original temporary filling, access is modified to gain straight-line access to the orifice of each canal before creating straight-line access to the body of each root. The use of ball-shaped ultrasonic tips can be a great help along with regular tapered tips. Note: It's important to remember that proper straight-line access is imperative for instrumenting a severely curved canal. Good access is key for clinical success. Fig. 4 Fig. 2 Higher magnification shows the isthmus connecting the MB1 and MB2 canals. Even though MB2 joins MB1 in this case, it's important to instrument this portion of the root canal to ensure proper cleaning and disinfection. Note: Ultrasonics are a great help in this part of the procedure, because of their ability to clean in a three-dimensional manner. A CBCT was obtained to fully evaluate the root anatomy and to formulate a treatment plan to manage the 90-degree curvature on the mesial root. The axial section shows the presence of an MB2 canal, while the coronal section through the MB root demonstrates that MB1 and MB2 join somewhere midroot. Note: The vast majority of mesial buccal canals (MB1 and MB2) do join together. This is why, for many years, molar endodontics worked, even though we weren't fully aware of the prevalence of additional canals. 38 JANUARY 2021 // dentaltown.com DT0121_Nasseh_Koch_Endo_MM.indd 38 12/16/20 10:45 AMhttp://www.dentaltown.com