and Objective: On the basis of etiology of aphthous ulcer, there are many factors, which cause this problem such as immunologic and hematologic disorders and emotional stress. For treating this disorder, it is recommended using a steroid drug. This study was performed to investigate one of the natural bases as a bioadhesive dosage form in the management of aphthous ulcer. Methods: In this experimental study, there were two groups. The first twenty persons received bioadhesive without

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... ne acetonide (As pilot study) for determining the rate of adherence and possibly side effects of the bioadhesive. The second twenty persons as case and control, with history of minor aphthous ulcer were selected and treated in two courses of disease, once with bioadhesive containing drug (Case) and once again without drug (Control). The data were statistically analyzed by using student t-test. Findings: In the pilot study group, duration of adherence on the oral cavity was more than 20 minutes and there were not side effects or undesirable reactions such as bad smell or taste. There was not significant difference in analgesia and healing time course between case and control groups. Healing time in case and control groups after treatment were shorter than before treatment (P<0.000). Conclusion: Using bioadhesive as coating and protective agent may cause reduction of pain and healing time course. Also, triamcinolone in bioadhesive don't affect on reduction of pain and healing time.