A 55-year-old woman came to a dentist with complaints of burning in her oral cavity when eating irritant foods, a sensation of roughness, and an unusual appearance of the buccal mucosa. The patient has a history of chronic cholecystitis. Objectively, she has artificial crowns made of various metals in her oral cavity Against the background of unchanged buccal mucosa, she has patches of small whitish papules in the retromolar space. They are keratinized, slightly raised, form a ring-shaped pattern, and cannot be removed by scraping. Make the provisional diagnosis.