Coffee is certainly a controversial beverage. There seems to be evidence that coffee can lower risk of stroke, improve diabetes, and lower stress. A study by the Journal of Conservative Dentistry showed that people who drink coffee have a lower prevalence of cavities than those who do not. However, these coffee drinkers drank the coffee black. When sugar and other additives are added to the coffee, the prevalence of cavities goes up.
What makes coffee a cavity fighter? Perhaps it is the antibacterial properties against the bacteria that cause cavities. Little is known at this point, but as long as the coffee is without milk and sugar it may actually fight decay!