I suppose it depends on how long you live, and some luck. My 82 year old stepfather, who is a retired dentist, has mostly okay teeth. My 75 year old FIL had to have some ugly gum work done, but he has okay teeth otherwise.

I am guessing that the better your teeth are at 15, the better they'll be at 45, and the better they'll be at 75. I have one crown, which I got at 38, which goes all the way back to a cavity I had as an early teen (which was filled, but was large, and eventually the tooth broke.) So some of it is cumulative.

Like many things a lot of the teeth stuff is genetic.

Yeah, I think most of teeth stuff is luck.

Well, and flossing, and not having a meth addiction, and so forth, also.

Yeah, I think most of teeth stuff is luck.

Or controlled by the Tooth Fairy.

I had to go in for implants last week and it was the absolute worst. Ghastly. But I do really like my dentist.

My implant wasn't the worst dental experience I've had, but it wasn't awesome.

If you take reasonably good care of your teeth and see a dentist twice a year, will your teeth probably remain mostly OK for the rest of your life?

I think generally yes, assuming (like flea said) some good luck/genetics. If you're seeing the dentist twice a year, they'll let you know if anything is amiss, and if you're not an ass like me and actually follow up on it, you should be fine.

and not having a meth addiction

Okay, I at least have that going for me.

I think some of it is nutrition as well. My mom and uncles were a little malnourished, and my mom had most of her bad teeth stuff happen in her early 20's. When she was in her mid 60s all the crowns fell out and she just had little stubs. So she got dentures.

I don't have great teeth, but my teeth in my early 40s are all my own, unlike my mom and uncles.

Well, and flossing, and not having a meth addiction, and so forth, also.

Sure, sure. And the nutrition stuff like Sophia said. But like, I've not had gum issues beyond the bleeding after ~40 years of not really flossing. I chalk that up to good luck. And my broken teeth/crown/root canal situations to bad luck!

With care and, as said, genetic luck, your teeth should do all right. By the time you're an adult you'll probably have a reliable indication, assuming you take care of them and visit a dentist regularly.

I had something awful happen to my teeth in my early teens (so permanent teeth, worse luck) and now have huge fillings and many crowns (with the promise of more to come) on my back teeth, where my braces were anchored. My mother's father, who was malnourished when he was young, had to get dentures at a fairly early age.