What happens when you leave a cavity untreated or unfilled?

It gets worse: Untreated cavities just get larger and deeper, and they lead to tooth breakage, nerve exposure, pain, infection, and in very rare instances hospitalization and/or death. They will also spread to other teeth. Instead of simple fillings, one would end up needing extractions, root canals, antibiotic treatment, crowns, or even dentures. If you value your teeth, fix them early on with fillings.

Lead to Infection: If a cavity is left untreated, the decay can make its way into the nerve of the tooth and casue an infection. The deeper the cavity gets the greater chance you will need a root canal or extraction of the tooth to remove an infection. If left untreated an infection in the mouth can cause serious illness and even death.