That's exactly what we're saying, you can submit without any DAT score at all if you've never taken it before, you just tell them when you're scheduled to take it. They'll see your DAT score of 19 no matter what, but that's the average accepted DAT, so why would they filter you out? SDN has a high-score bias because high scorers want to show off and low scorers don't, but 16s-18s get accepted every year. Just inform every school that you have a retake planned (if it's not part of AADSAS somewhere, email their admissions offices directly, I don't remember specifically if it's on there). Nobody who isn't actually on an adcom can tell you what their exact protocol is, but since we know that applicants are allowed to submit without a score and that dental schools encourage you to send them updates to your application throughout the cycle, we can only assume they'll either look at a scoreless applicants and say they'll interview them if their score comes in higher than x, or that they won't look at them at all until the score gets in. Since you already scored the accepted average, you have absolutely nothing to lose applying ASAP, you have a really good shot at getting some interviews already, your GPA isn't that low. Schools that like your whole app might invite you right away. Others might hold off judgment knowing you're retaking, if you send them a 22, 23, 24 in a few weeks, they certainly will take another look.
Regarding supplemental essays, yes, you just have to go to every single school's website and find the supplemental application info. It's a pain in the butt. Some schools want essays, some literally just want another $100 check sent in the mail.
One last thing, I said your GPA isn't that low, but it is kinda low. You should almost certainly apply to at least 10ish schools if you want a decent chance of getting accepted. There are varying opinions on this but if I remember right the stats show that fewer than that with average stats and there's a pretty decent chance of no acceptances. Having to reapply means you pay application fees and buy flights and hotels again, losing 1 year of $100000+ income, plus paying higher tuition for your whole education since it rises ever year. It's absolute worth another $500 right now to increase your overall chance of acceptance this year. Get a credit card if you have to. Also, make sure you know whether or not every school you apply to tends to accept students from your state and probably avoid entirely the schools that take very few OOS applicants like UNC, UConn, etc. If you do score really high on the DAT and one of those is your dream school, you can add them later but I'd argue it's not worth the fee when a 19 isn't high enough for one of 3 or 4 highly competed OOS seats.
