Microwave ovens sometimes produce food that is cold externally and very hot internally, and this has led to a rise in the frequency of intra-oral thermal burns. Thermal food burns are usually on the palate or posterior buccal mucosa, and appear as zones of erythema and ulceration with necrotic epithelium peripherally. Electrical burns more commonly affect the oral commissure (corner of the mouth). The lesions are usually initially painless, charred and yellow with little bleeding. Swelling then develops and by the fourth day following the burn the area becomes necrotic and the epithelium sloughs off.Electrical burns in the mouth are usually caused by chewing on live electrical wiring (an act that is relatively common among young children). Saliva acts as a conducting medium and an electrical arc flows between the electrical source and the tissues, causing extreme heat and possible tissue destruction. Chemical injury
Caustic chemicals may cause ulceration of the oral mucosa if they are of strong-enough concentration and in contact for a sufficient length of time. The holding of medication in the mouth instead of swallowing it occurs mostly in children, those under psychiatric care, or simply because of a lack of understanding. Holding an aspirin tablet next to a painful tooth in an attempt to relieve pulpitis (toothache) is common, and leads to epithelial necrosis. Chewable aspirin tablets should be swallowed, with the residue quickly cleared from the mouth.Other caustic medications include eugenol and chlorpromazine. Hydrogen peroxide, used to treat gum disease, is also capable of causing epithelial necrosis at concentrations of 1–3%.
Signs and symptoms
Common symptoms present in the different types of leprosy include a runny nose; dry scalp; eye problems; skin lesions; muscle weakness; reddish skin; smooth, shiny, diffuse thickening of facial skin, ear, and hand; loss of sensation in fingers and toes; thickening of peripheral nerves; a flat nose from destruction of nasal cartilage; and changes in phonation and other aspects of speech production. In addition, atrophy of the testes and impotence may occur.Leprosy can affect people in different ways. The average incubation period is five years. People may begin to notice symptoms within the first year or up to 20 years after infection. The first noticeable sign of leprosy is often the development of pale or pink coloured patches of skin that may be insensitive to temperature or pain. Patches of discolored skin are sometimes accompanied or preceded by nerve problems including numbness or tenderness in the hands or feet. Secondary infections (additional bacterial or viral infections) can result in tissue loss, causing fingers and toes to become shortened and deformed, as cartilage is absorbed into the body. A persons immune response differs depending on the form of leprosy.Approximately 30% of people affected with leprosy experience nerve damage. The nerve damage sustained is reversible when treated early, but becomes permanent when appropriate treatment is delayed by several months. Damage to nerves may cause loss of muscle function, leading to paralysis. It may also lead to sensation abnormalities or numbness, which may lead to additional infections, ulcerations, and joint deformities.