An 18-year-old student complains of roughness and dryness of mucous membrane of the oral cavity. He always bites uncontrolledly off mucous membrane along the line of teeth joining. The patient suffers from chronic cholecystitis, he is smoker. Hygiene index is 2,3. Objectively: mucous membrane along the line of teeth joining is quaggy, edematic, whitish. What is the leading factor of this disease development?