Aphthous stomatitis

Aphthous stomatitis is "a recurrent disease of the oral mucosa of unknown etiology. It is characterized by small white ulcerative lesions, single or multiple,  round or oval. Two to eight crops of lesions occur per year, lasting for  7 to 14 days and then heal without scarring."

Treatment
A tube of 5 gram tube of ointment, containing 5 mg dexamethasone, can be used on ulcers 3 times a day after meals for 5 days. In a randomized controlled trial, the relative risk ratio of dexamethasone ointment, as compared to placebo, for nonhealing at 6 days was 0.4 and the relative risk reduction was 62.2%. In populations similar to those in this study which had a rate of risk as measured by the nonhealing at 6 days of 45% without  treatment, the number needed to treat is 4.