Gums become inflamed or swollen and may bleed when brushed. This early stage is known as gingivitis. If gingivitis is not treated, periodontitis can develop. If periodontitis is not treated it can lead to a loss of supporting bone in the jaw that surrounds teeth. Eventually teeth may fall out.
This is also known as dental caries or dental decay. Dental decay happens when the enamel and dentine of a tooth become softened by acid attack after you have eaten or drunk anything containing sugars. Over time, the acid makes a cavity (hole) in the tooth.