Oral hygiene is the practice of keeping one's mouth clean and free of disease and other problems (e.g. bad breath) by regular brushing of the teeth (dental hygiene) and cleaning between the teeth. It is important that oral hygiene be carried out on a regular basis to enable prevention of dental disease and bad breath. The most common types of dental disease are tooth decay (cavities, dental caries) and gum diseases, including gingivitis, and periodontitis.General guidelines suggest brushing twice a day: after breakfast and before going to bed, but ideally the mouth would be cleaned after every meal. Cleaning between the teeth is called interdental cleaning and is as important as tooth brushing. This is because a toothbrush cannot reach between the teeth and therefore only removes about 50% of plaque off the surface. There are many tools to clean between the teeth, including floss, flossettes, and interdental brushes; it is up to each individual to choose which tool he or she prefers to use.

Sometimes white or straight teeth are associated with oral hygiene, but a hygienic mouth may have stained teeth and/or crooked teeth. For appearance reasons, people may seek out teeth whitening and orthodontics.