Which of the following is NOT an appropriate treatment for recurrent aphthous ulcers (canker sores)?

Recurrent aphthous ulcers (RAU) are self-limiting lesions with a characteristic clinical appearance (well-defined, round/oval, painful ulcers with a yellowish fibrinous base and erythematous halo) that do not require excisional biopsy for diagnosis. Excisional biopsy is performed to diagnose lesions of uncertain or potentially malignant nature — not for lesions with a clear clinical diagnosis. Treatment of RAU includes topical corticosteroids (first line), antimicrobial mouthwash (chlorhexidine), laser therapy for pain relief and healing promotion, and topical anesthetics. Incisional biopsy may be performed if a lesion fails to heal or looks atypical.