system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: How do your gums hold onto your teeth?
gpt
Dentist here. Imagine how velcro works. There's hooks on one side and loops on the other. The hooks attach to the loops and are stuck. In a similar sense, your gums are actually attached directly to your tooth with ligament fibers, which are like the hooks. These fibers in the gums are collectively called the periodontal ligament (PDL). So what does the PDL attach to on the tooth? Your tooth has a layer on the roots called cementum (this is the loops). So your gums are stuck onto your tooth this way. But this is one velcro you don't want to pull off. It's rare for it to reattach back the same way once the gum is separated from your teeth. 

It's a liiiitle more complicated than that in reality, but that's the gist of it.