Take an x-ray. Please!
As I travel around dental practices I observe a consistent and very common problem.
Without any doubt in my mind, the most common, preventable cause of mistakes in dentistry is failure to take an x-ray. In particular, a well exposed periapical.Some typical examples of mistakes I've seen:
A crown made on a tooth with a large periapical area associated with a failing root filling
A dentist starting a root filling on an unsavable tooth
A patient who was treated for 5 visits for TMJ problems when they had a carious pulp exposure on a lower molar
A dentist filling the mesial of a tooth and missing decay on the distal of the same tooth
Taking an x-ray is of benefit to all concerned - you avoid errors, you locate problems, you foresee difficulties and you get paid for taking it. What a win-win. You earn more money and the patient gets higher quality treatment.
My rule is that I would never work on (or extract) any tooth if I didn't have a current periapical film of that tooth.