OBJECTIVE: To evaluate the onset of analgesic effect for a new formulation of ibuprofen sodium dihydrate versus conventional ibuprofen (ibuprofen acid). MATERIALS AND METHODS: In this randomized, double-blind, double-dummy, crossover trial, patients requiring surgical removal of two impacted or partially impacted mandibular third molars received: ibuprofen sodium dihydrate 400 mg plus conventional ibuprofen placebo (Group 1); or conventional ibuprofen 400 mg plus ibuprofen sodium dihydrate placebo (Group 2) following the first surgery. Patients were then crossed over to the alternative treatment. RESULTS: 72 patients were enrolled in Group 1 and 72 patients in Group 2. Ibuprofen sodium dihydrate produced faster initial pain relief than conventional ibuprofen as assessed by time to first pain relief (24.6 vs. 30.5 minutes; p = 0.004), and patient-assessed pain relief at 15 minutes ("some" to "complete" pain relief: 43% vs. 29%; p < 0.001) and 30 minutes (82% vs. 63%; p < 0.001) and pain intensity at 30 minutes (p < 0.001). Substantial pain relief with ibuprofen sodium dihydrate was twice that of conventional ibuprofen at 30 minutes (11% vs. 5%; not significant); 29% and 33% of patients did not reach substantial pain relief at 120 minutes. There were no adverse events leading to treatment discontinuation and only two serious adverse events (oral abscess and facial paresis with conventional ibuprofen) considered unrelated to treatment. CONCLUSIONS: Ibuprofen sodium dihydrate was as effective as conventional ibuprofen, but had a faster onset of initial pain relief and significantly reduced pain intensity within the first 30 minutes after administration, providing rapid clinically meaningful pain relief for patients.