What can happen if you left a cavity in her mouth without treatment? Dental caries is comparable to infection. It consists of harmful microbes that use sugar to alter the tooth. Over time, this will form a small hole in the tooth, and if not repaired with a filling, the decay will continue to grow.
If decay is left untreated, it can possibly ruin a good part of the tooth. This could make it difficult to repair by a conventional seal. If a large portion of the tooth is destroyed, only crown can restore it.
If micro-organisms of decay reaches the pulp chamber, where the nerves and blood vessels are located, the pulp becomes irritated and infected. This can eventually lead to the formation of a dental abscess can cause much pain. Only a root canal can then repair a tooth whose pulp is infected, and a crown will probably be needed later as final restoration.
There are also situations where a tooth is so destroyed by caries that nothing can be done to fix it, not even a root canal or a crown. In this case, the tooth has unfortunately need to be extracted.