The bottom line is, if done incorrectly, lip piercings can destroy your teeth. To combat this, work closely with your piercer to make sure your jewellery fits. When done right, Gottschalk says the piercing should "nest" and tuck into your lip, which is your body's natural way of keeping the jewellery off of your teeth. Once it's been downsized, the piercing also shouldn't stick out too much from your lip.
Any implant grade metal works best, but metal is harder than your teeth, so if you've had extreme dental work, consult your piercer beforehand about any potential risk. While oral damage of some kind is to be expected with lip piercings, Beall says it should be pretty minimal if the placement of the piercings is correct, with the jewellery more towards the gum line rather than the teeth. Beall also prefers titanium studs for "snake bites" with flat discs on the inside to reduce damage.