Pain after root canal treatment with various apical finishing sizes

A recent study revealed that the size of apical preparation had a significant impact on postoperative pain levels. The results of this study were published in the journal BMC Oral Health. 
In this study, fifty teeth belonging to twenty-five individuals were separated into two equal groups, with twenty-five teeth in each group using E3 Azure rotary files. Group A was expanded by two sizes in relation to the Initial Binding File (IBF), extending to 40#/0.04 for the distal canals and 35#/0.04 for the mesial canals. Group B, on the other hand, was expanded by three sizes larger than the IBF: 45#/0.04 for the distal canals and 40#/0.04 for mesial canals. Patients were asked to rate their pain levels on a modified VAS form and describe their pain intensity at twelve, twenty-four, and seventy-two hours, as well as after a week. VAS data were analyzed using Freidman's test, Nemenyi post hoc test for intragroup comparisons and signed-rank test for intergroup comparisons.
The outcomes revealed that irrespective of the timing of the measurement, an enlargement of the apical preparation was significantly linked to increased pain scores (p value < 0.001). In both groups, there was a significant decline in reported pain scores over time, with scores at twelve-and twenty-four hours post-treatment significantly higher than those at other intervals (p value < 0.001). Additionally, pain scores at three days post-treatment were significantly higher than those at one week (p value < 0.001).
Thus, it can be concluded that apical preparation size significantly influenced postoperative pain levels.