An aphtha is an ulcer in the oral cavity and is one of the most common diseases of the oral mucosa. It is usually white, sometimes yellow, with a characteristic red border on the mucous membrane. It forms a light-coloured bubble which may develop into a smaller or larger ulcer on the bottom of the gums, on the tongue or the inside of the lips.

Epidemiological data show that diabetes is one of the main risk factors for periodontitis or periodontal disease (colloquially periodontitis). The susceptibility to periodontitis increases by about three times in people with diabetes. Gum disease is one of the consequences of unmanaged diabetes. Oral health is an essential component of the management of this chronic disease.