A tooth infection that is left untreated can spread and get worse.
When the tooth infection spreads and gets worse then it can lead to infecting your blood and even your heart and cause serious health issues that can potentially be life threatening.
Most tooth infections are nothing to worry about and go away on their own even without treatment however in rare cases a tooth infection can be serious enough to cause a heart attack, heart disease and even death.
Usually you'll know when a tooth infection is getting worse or more severe as you'll usually have a fever and or swelling of the gums or your mouth.
If you do have a fever and swelling or one or the other go to the emergency room or get to your dentist as soon as possible so that the tooth infection can be stopped and treated.