system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why is it that you can break a piece of a tooth and it doesn’t need fixing, but if you have the tiniest cavity it has to get filled ASAP?
gpt
A cavity is decay-it is dead and dying areas with bacteria, and can spread if not taken care of. A cracked broken piece of tooth, depending on how deep the break is, won't cause increasing problems over time.