Sometimes halitosis or bad breath is not due to oral hygiene. There are several other reasons so need to be clinically correlated.
Respiratory tract infections? sore throat, swollen lymph nodes (" swollen glands") in the neck, fever, stuffy nose, a greenish or yellowish nasal discharge, a mucus-producing cough external agents? cigarette stains on fingers and teeth, a uniform yellow" coffee stain" on teeth dry mouth? difficulty swallowing dry foods, difficulty speaking for a prolonged period because of mouth dryness, a burning sensation in the mouth, an unusually high number of dental caries, dry eyes (in sjgren's syndrome) systemic (bodywide) illnesses? symptoms of diabetes, lung disease, kidney failure or liver disease.