Apical Size and Root Canal Treatment Success Trial

This study is looking into two different ways to perform a root canal treatment. The study will look at differences and compare the two different treatment options over a 2-year period.More specifically, this study evaluates a small "skinny" root canal shape compared to a larger "broad" root canal shape and if this affects the success of the root canal treatment. Both types of treatment are standard of care and aim to treat the infection inside your tooth. When a tooth is infected with bacteria, we can see a dark area on the radiograph around the roots of the infected tooth. If this dark area becomes smaller or goes away completely after root canal treatment and you do not feel any pain or other symptoms, then we know that the treatment was successful and there is no need for further treatment on this tooth. To measure the size of the dark area around the tooth (i.e. volume) before and after the treatment we will need to take two limited volume three-dimensional radiographs (cone beam computed tomography-CBCT), one prior to treatment and one at two years after the root canal treatment is completed. These radiographs are more accurate in detecting changes in lesion size than the regular periapical radiographs. We will assess the changes in lesion volume for all teeth included in the study and that will help us find differences in success between the two root canal treatment protocols, We are specifically looking for persons that have been diagnosed with a necrotic permanent mandibular molar with an evident radiographic lesion (i.e. dark area around the tooth) that can be retained in the mouth with root canal treatment and permanent restoration. This study place participants in different treatment groups after randomization. Randomization means that you are placed by chance (like flipping a coin) into a treatment group. For this study, there are two treatment groups (protocol) and they are listed below. Protocol 1: Group S: Root canal treatment will be performed in 2-visits using hand files and rotary instruments to a final canal shape of size #25. Protocol 2: Group L: Root canal treatment will be performed in 2-visits using hand files and rotary instruments to a final canal shape of size #35