Abstract: PURPOSE: To evaluate the incidence of pain during intracanal medication before and after root canal instrumentation for therapeutic reference. METHODS: Three hundred and twenty four teeth were selected in this study, and the teeth received root canal therapy with crown-down technique using ProTaper rotary system, followed by calcium hydroxide intracanal medication. The degree of reported pain was recorded as 4 levels after treatment according to the Negm criteria. The incidence of endodontic interappointment emergencies (EIAE) at various recording times starting from root canal preparation was evaluated based on the results analyzed with MATLAB and SPSS19.0 software package. RESULTS: All patients reported of pain immediately after root canal therapy and calcium hydroxide intracanal medication, of which 1.54% were diagnosed as EIAE, the prevalence and degree of pain were increased. The prevalence of EIAE reached 25.62% one day after treatment, and decreased to 3.70% 3 days later. Most of the pain released without treatment; however, few patients experienced severe pain. The relationship between the EIAE percentage and time duration after treatment was fitted by using MATLAB as P(t)=100%×0.066t exp (t: hour; RMSE=3.91). The patient started to report free of pain 6 hours after the treatment, 33.64% of the patients were painless 1 week after treatment, and 82.71% were painless 2 weeks later. There was significant difference between the pain level before and 2 weeks after treatment (P<0.01). CONCLUSIONS: During root canal preparation and intracanal medication, the prevalence and degree of pain were increased immediately after treatment, decreased 3 days later, and most of the pain was released 2 weeks after treatment.

Key words: Root canal therapy, Root canal instrumentation, Intracanal medication, Endodontic interappointment emergencies