In the early stages of gingivitis, bacteria in plaque build up, causing the gums to become inflamed and to easily bleed during tooth brushing. Although the gums may be irritated, the teeth are still firmly planted in their sockets. No irreversible bone or other tissue damage has occurred at this stage.
The good news is that you can prevent and reverse gingivitis by simply brushing your teeth, flossing, and having regular dental cleanings and checkups with your dental professional.