I think teeth is a problem for inexperienced suckers. Any competent deepthroat sucker surrounds his teeth with his lips and avoid the slightest of contact with the teeth at all times.
For example, my partner is just above normal size and I only lip-protect when taking it in, mostly to create some resistance as I slide my folded lips on his dick; when taking it out, my lips grab it and pull it gently while I am resurfacing it. Both movements are to mimic the push-pull effect of a handjob. It's pretty awesome technique since most guys I've done that came without touching their cock in any other way. Anyway, I never touched him with my teeth not even for a second, not even when I suckle him while deepthroating or when ballsurfing him (deepthroat him and then stick my tongue out to lick his balls or the area around his cock).
Even for a good sucker, though, if the cock is too thick and the top tries to throatfuck you, the lip protection might slip for a second (happened with another, super thick guy once), which is the reason throatfucking is either for the most advanced deep suckers or for non-super-thick cocks.