Is it a bad idea to take halcion (triazolam) before a wisdom tooth extraction?

Yes: You should discuss any medications that you may want to take with your surgeon before you have surgery. In addition, halcyon will affect your ability to give consent for the surgery.

Follow pre-op orders: If you are scheduled to have wisdom teeth removed, take only the medications approved or prescribed by your dentist or surgeon. If you are extremely anxious about your surgery, your dentist or surgeon may prescribe something for you to take prior to your appointment.

No: As long as your dentist/surgeon is aware and approves before you take it, it should be just fine. In fact, it is often recommended!