If your dentist detects a small area of erosion on your enamel before it reaches the dentin, he may suggest an approach that would help repair the spot. This process might include using mouth rinses, toothpastes or filling materials that contain fluoride, calcium and phosphates.
When decay reaches the dentin, there is no turning back. A small cavity can be repaired with either an amalgam filling (composed of silver and other metals) or a tooth-colored resin material. If the tooth has lost a lot of its structure, however, your dentist may need to do a crown. Crowns strengthen and restore shape and function to your teeth, but they cost quite a bit more than a simple filling.
An abscessed tooth is the worst-case scenario, and your treatment options are slim. You can either opt for a root canal treatment or an extraction, though dentists will typically only do extractions when there are no other means of saving the tooth. Should you require a root canal, your dentist or an endodontist will remove the diseased pulp and clean and seal the pulp chamber; the Journal of Clinical and Diagnostic Research's article contains more details about this process. After root canal treatment, teeth can become more brittle and break easily. If you have lost a lot of tooth structure due to decay, your dentist may also recommend a crown for your tooth.
Do you see a pattern here? The longer you put off dental treatment, the more involved and expensive it becomes — and the more pain you may have to endure. The moral of this story is to go to the dentist at the first sign of trouble. Better yet, prevent tooth decay from occurring by brushing and flossing daily, and visiting your dentist regularly for a more thorough cleaning and check-up.