INTRODUCTIONMost pain studies have been based on a postsurgical, third molar model using ibuprofen (IBU)/acetaminophen (APAP). Studies have found quicker onset of pain relief with a newer formulation of IBU - ibuprofen sodium dihydrate (ISD). The purpose of this study was to compare pain reduction of ISD/APAP to ISD in an acute endodontic pain model of untreated patients experiencing moderate to severe pain with symptomatic apical periodontitis.METHODS AND MATERIALSIn this double-blind randomized study, 64 adult emergency patients in acute moderate to severe pain, a pulpal diagnosis of symptomatic irreversible pulpitis or necrosis, and symptomatic apical periodontitis participated. Each patient randomly received either one dose of 768 mg ISD/1000 mg APAP or one dose of 768 mg ISD. Pain intensity scores were recorded every 15 minutes over 240 minutes using the Heft-Parker VAS along with time to first sign of pain relief, time to meaningful pain relief, and time to 50% pain relief also recorded. The data were analyzed statistically.RESULTSBoth ISD and ISD/APAP groups showed a progressive decrease in pain from baseline to 120 minutes after medication administration. Afterward, a relative plateau was seen in the patients' pain. There was no difference in the VAS scores between the ISD and ISD/APAP at any given time point, time to first sign of pain relief, time to meaningful pain relief, and time to 50% pain relief.CONCLUSIONSThe addition of APAP to ISD for pain control in an untreated endodontic pain model did not differ significantly from ISD alone.