Need advice! Insurance won’t cover dental work

Sorry if this is the wrong place to post this, r/advice said no medical or insurance related questions so figured this would be the next best place. It’s kind of a long story but basically my last dentist ignored that I had fluorosis and a very severe cavity, once I moved cities and went to a new dentist they told me that I have an abscess from the cavity that went untreated which needs a root canal and I need 8 crowns from letting the fluorosis go untreated for so long. Everything all together would cost about $5000. I have dentaquest through molina medicaid but they said they wouldn’t cover anything. My dental coverage expires when I turn 20 in a couple months anyways so I was thinking about just paying for my own dental insurance but I’ve read that they have a yearly limit on what they will cover. I just moved out a year ago and am struggling to get by so I really can’t afford $5000 out of pocket, I don’t have any credit so I’m not sure if I’ll get approved for any payment plans. I’m in a lot of pain and am visibly watching my teeth just rot away but I have no idea what to do about this. Sorry for the long post, any advice would be greatly appreciated!!!