I'd been drinking apple juice in similar quantities before and since for years (when I say "started" I really mean I switched from apple to orange), which I believe has similar sugar content.
Don't know about your teeth, but that sugar is pushing for diabetes. Drinking juice straight (not diluted with water) at 100+ kCal/cup rate, in quantity, is a bad idea
Yeah, this is a few years back now; I spoke to a nutritionist last year for the first time in my life and that was the first thing she told me to cut (and I have).