I think your life will be immeasurably simpler if you firmly abstain from any illicit drugs of any kind, Stacey--pot, oxy (whatever it is!), or otherwise. If you need pain killer for your teeth, the dentist can provide them or you can buy topical ointments at the pharmacy. If all your friends know that you just don't do any of those drugs, it will become a nonissue.
Of course, hanging out with someone who "say[s] over and over, all I want is a buzz," is putting yourself in one of those situations that you should be planning for--either by avoiding the situation in the first place (best plan!) or by just leaving when it begins to compromise your decision to abstain from all drugs.
It seems to me that you're anxious about how they'll react if you say no. Don't worry about that!
Don