OTC painkillers do absolutely nothing for me. (If you have any access to stronger painkillers use it...) If it's a tooth pain from a cavity maybe one of those Ambesol or clove oils might help, but I've never tried these.
You might consider some booze and some sleeping pills (or benadryl), something with Diphenhydramine HCL in it. (if drinking, make sure it's plain D HCL and does not contain anything elses) I the standard dose is 50 mg, but if you drink (not stinking drunk, but a good few drinks...) and take maybe 75-100 mg this will knock you out and you will sleep like a rock tonight, and you'll be dozing off much of tomorrow. Do the same tomorrow night, then you can do a more normal (50 mg) dose sunday night. Monday comes and you're off to the dentist.
This way you will have slept off most of the time with pain.
I know drinking and overdosing sounds bad and I won't argue that fact. I will say that I have taken rediculous doses of OTC sleeping pills (due to increasing tolerance) for extended periods of time + drinking, and I've never had any bad health resulting or anything show up as abnormal in bloodtests in yearly checkeups since then.
I've done the whole prescriptions pills + OTC + drinking thing for a few years (trying to fix insomnia, only made it worse in the long run though...), and got off it. It hasn't effected my health so I think I stopped before doing any real damage. A couple of nights of this though should be safe enough.