Mesalazine Sustained-Release Tablets and 0.02L glycerol mixed, 2.5% mesalazine glycerol suspension liquid, gently apply to the ulcer surface, 3 times/day. Daily treatment time of the drug is 8 am,12 pm and 4 pm.

wipe the riboflavin sodium phosphate injection to the ulcer surface, 3 times/day. Daily treatment time of the drug is am,12 pm and 4 pm.

Mesalazine sustained-release tablets 500mg and 0.02L glycerol mixed, the preparation of 2.5% the mesalazine glycerol suspension liquid, gently apply to the ulcer surface, 3 times/day. The application time of the drug is 8:00,12:00, 16:00. Daily 20:00 measure the size of the mouth ulcers and record the symptoms in the diary card.

The primary outcome is ulcer healing, oral ulcer area can be divided into 3 degrees: 1 degrees for a single ulcer, area ≤ 8mm; 2 degree for a single ulcer, 8mm ≤ area ≤ 15mm, or two ulcers, area of every ulcer ≤ 8mm; 3 degree for a single ulcer, area ≥ 15 mm, or 2 ulcers, every area between 8 to 15mm. Recovery refers oral ulcer is healing completely. The effective is the ulcer area decrease more than 1 degree. Invalid means the ulcer area is no change.

to observe the recurrence rate of ulcer

Symptom effective rate =（total score before treatment - total score after treatment）/total score before treatment x 100%. Total score = frequency + severity. Frequency score is calculated by all the frequency of oral pain, anorexia,and eating difficult. Severity is accumulated by the degree of symptoms described above,which is divided to 4 degree as 0 presenting none,and 3 presenting most severe.