Scientists have identified two substances in licorice used extensively in Chinese traditional medicine that kill the major bacteria responsible for tooth decay and gum disease, the leading causes of tooth loss in children and adults.

They say that these substances could help in treating and preventing tooth decay and gum disease.

Stefan Gafner and colleagues explained that the dried root of the licorice plant is a common treatment in Chinese traditional medicine, especially as a way to enhance the activity of other herbal ingredients or as a flavouring substance.

Despite the popularity of licorice candy in the U.S , licorice root has been replaced in domestic candy with anise oil, which has a similar flavour.

Traditional medical practitioners use dried licorice root to treat various ailments, such as respiratory and digestive problems, but few modern scientific studies address whether licorice really works.

To test whether the sweet root could combat the bacteria that cause gum disease and cavities, the researchers took a closer look at various substances in licorice.

They found that two of the licorice compounds, licoricidin and licorisoflavan A, were the most effective antibacterial substances.

These substances killed two of the major bacteria responsible for dental cavities and two of the bacteria that promote gum disease.

One of the compounds licoricidin also killed a third gum disease bacterium. The researchers said that these substances could treat or even prevent oral infections.