Gum diseases are among the most common chronic human diseases, affecting between 20 to 50% of people worldwide. They happen when plaque, a sticky film of bacteria, builds up on teeth. The earliest stages of gum disease are treatable and reversible (gingivitis). But some people develop a chronic destructive form of gum disease, which is irreversible. This disease progresses to tooth loss. A growing body of evidence shows that gum disease can also make people more likely to develop other serious health conditions.