A new study suggests that drinking black coffee may also help people maintain a healthy set of teeth. For the study "Antibacterial effect of coffee: calcium concentration in a culture containing teeth/biofilm exposed to Coffea Canephora aqueous extract," which was published in Letters in Applied Microbiology June 7, researchers from Rio de Janeiro, Brazil found that coffee that contains high amounts of caffeine can destroy bacteria that cause dental plaques.

"Dental plaque is a classic complex biofilm and it's the main culprit in tooth decay and gum disease," said study researcher Andrea Antonio, from the Federal University of Rio de Janeiro in Brazil.

Unfortunately, coffee drinkers may not be able to enjoy the dental health benefit of coffee if they add sugar, milk, or cream because these will give teeth the opposite effect. Coffee should be black, strong, and unsweetened in order to have a positive effect on oral health.

For their study, Antonio and colleagues used bacteria in the saliva to cultivate biofilms in fragments of milk teeth that were donated by children. They then treated the teeth daily with an extract of the coffea canephora. Also known as Robusta coffee, this particular variety of coffee, which makes up about 30% of the coffee produced worldwide, is mostly grown in Vietnam, Brazil, and Africa. Earlier studies showed that Robusta coffee contains high amounts of polyphenols, compounds that are known to prevent and treat oral diseases.

The researchers observed that the fragments that were treated with Robusta coffee extract appeared to have been lysed, a process wherein the polyphenols destroy the bacteria on the teeth by bursting them open. After a week, the researchers also observed that the teeth that were exposed to coffee extracts appeared to be in better condition compared with those that were treated only with filtered water.

Despite the study finding association between strong coffee and dental health, Antonio warned against drinking too much coffee. Although coffee can help destroy plaque-causing bacteria, she said that excessive coffee consumption may also cause staining and the coffee's acidity may negative impact the tooth enamel.

Other food products that are known to have a positive effect on dental health include cheese and yoghurt because of their calcium content, as well as green tea, grapes and coffee because of their antibacterial properties.