How effective is whiskey or mixed drink for a toothache?

Not Effective. I guess if you're drunk enough, you won't care about your toothache for a while, but alcohol doesn't cure or help a toothache in any significant or long-term way. Your symptoms may subside for a while, but they will definitely come back vehemently in the future. The only way to take care of this problem is to see a dentist. The sooner the better!
Minimal. The alcohol may help decrease the pain but does nothing for the cause. Depending on how much whiskey you need for the pain may incur a secondary problem- a hangover. See a dentist. You can also try homeopathic hypericum for the toothache. You may also find acupuncture can help as well. See a dentist.