So it all depends on the state of the tooth. If your cavity just started, a fluoride treatment(tap water toothpaste, and mouth rinses) may help restore your tooth's enamel and can sometimes reverse a cavity in the very early stages. Professional fluoride treatments contain more fluoride though. But when the tooth can't be saved due to severe rot, your dentists should extract the tooth and replace it with a denture, bridge, or an implant. But overall, its better if you see a dentist and learn the state of the tooth and the better treatment option. Hope it helps.