What should you do when you break part of a tooth off on a holiday weekend?

Call your dentist: Most dentists will be available to treat their patients in an emergency so call your regular dentist, especially if you have pain. If it a minor problem with no pain, swelling, or bleeding you can wait until the holiday is over to call.

Emergency: My advice would be first to call your own dentist. Often they have emergency number or service to get after hour messages and will get back to you. Sometimes just hearing from them puts your mind at easy, knowing they are there for you if you really need them in a pinch. They may have alternate doctor covering for them when not available. There are some 24\7 emerg services but try to avoid them.