Where can a cavity spread to?

Lot's of bad places: I assume you mean a dental cavity. This can cause an abscess if untreated and can spread to your sinuses and even your brain (upper jaw) or all the way down to your heart (lower jaw). Lest we forget, tutankhamun, the boy-king of egypt ("king tut") was thought to have died of a brain abscess from a cavity. Go see your dentist!

Cavities Spread: All cavities start small... 1 surface of decay. The cavity spreads which results in 2 surfaces of decay. If left untreated the decay continues to spread & becomes a 3 surface cavity. Then it moves on to a 4 surface cavity. It becomes too large to fill the decayed area & a crown is needed. Deep cavities also can lead to root canals. Best to treat the 1 surface cavity & avoid crowns & root canals.

Close by: Since cavities are bacterial in nature the adjacent teeth can be affected. This is why flossing is so important. High levels of bacteria in the mouth and food debris together cause cavities.

Jaw: A cavity, left untreated, can spread to your jawbone, blood stream, spine, and/or your brain. Don't leave a cavity untreated!

Outside in: A cavity typically starts in the biting grooves or smooth services in between teeth. They start from the outside in. Enamel--> dentin --> pulp.

Usually to the pulp: Cavities start off small on the tooth surface, called the enamel. The cavity penetrates the middle layer of the tooth, called the dentin, and eventually spreads to the pulp that consists of the blood supply and nerve of the tooth. At this point, the patient usually will have a toothache.