What tests are needed before determining whether a tooth requires root canal treatment or not?

Several: Depending on the need and individual situation, a dentist may perform percussion tests, vitality tests with hot liquid and possibly ice. An x-ray is required to see the end of root where the proposed root canal will occur but is not the only diagnostic tool needed to assess the health (or lack therof) of the nerve.

No one test: In some cases the need for a root canal is obvious as in a draining abscess or a clear sign on an x-ray. In some situations the tests are relative. Generally pain to cold or especially heat that is prolonged is an indication of irreversible damaged, necessitating a root canal. An electric pulp tester, percussion and palpation may also be used.

Vitality tests: Percussion, palpation, hot, cold and electric pulp testing. X-rays are also considered valuable.