Abstract: Objective To study the effectiveness and security of Pudilan Keyanning toothpaste on the treatment of recurrent aphthous ulcer(RAU). Methods A randomized, doubleblind, placebocontrolled clinical trial was applied in the treatment of RAU. 40 cases in the experimental group and the other 40 cases（39 cases finished） in the control group were administered with Pudilan Keyanning toothpaste and placebo respectively on the ulcer twice a day for 6 days. The effect was evaluated by ulcer healing ratio, ulcer healing time, change of pain indexes, ulcer area, exudates and hyperemia score of ulcer. Safety of the toothpaste was monitored by adverse even (AE) observation. Results Treatment was completed,40 and 39 cases in the experimental and control groups respectively. The ulcer healing ratio of two groups was 95.00% and 51.28% respectively at day 6（P<0.05）. DR (Days) of 50% cases in the experimental and control groups were 5 and 6 respectively. Comparisons of pain indexes, area of ulcer, exudates and hyperemia score of ulcer at day 6 showed remarkable significance. No AE related to the toothpaste occurred in the two groups. Conclusions Pudilan Keyanning toothpaste is effective and safe in the treatment of RAU. 

Key words: recurrent aphthous ulcer, Pudilan Keyanning toothpaste, randomized doubleblind trial