Although the literature may show that there is no difference in treating cases in one vs. two visits, I almost always treat cases with symptomatic apical periodontitis in multiple visits. The main reason is for predictability: I can make sure that we are able to resolve the symptoms prior to finishing the case. A second reason is that we can use calcium hydroxide to help disinfect the root canal system. In the last few years, technological advancements in irrigation have been shown to increase the efficacy of irrigants at disinfecting canals. For patients who have difficulty tolerating dental treatment, the potential exists to treat these case types in a single visit.
Above is a two year recall of #12. The tooth initially presented with a necrotic pulp and an acute apical abscess (acute exacerbation of chronic apical periodontitis, or “Phoenix Abscess”), and a buccal space infection. EndoVac apical negative pressure irrigation was used and treatment was completed in one visit for this 82 year old. Note that the canal shapes are still conservative (30-06). A fiber post was bonded into each canal. The two year recall shows success, with resolution of the periapical radiolucency, and the return of the radiographic PDL space and lamina dura.