I’ve been asked to comment on anaesthetic testing of teeth. This is a diagnostic test that’s done to try to localize pain to a particular area or tooth or to even rule out odontogenic aetiology as the source of pain.

While I was an endo resident I rotated through Mt. Sinai’s facial pain clinic and one thing that I’ll probably remember forever is a patient who presented with a nagging toothache. She pointed at the 16. I don’t remember her history, but for some reason her regular dentist suspected non-odontogenic pain. We suspected the same thing once we saw her and examined the area. My supervisor at the time recommended that we try an anesthetic test to see if we could rule the tooth in or out as a source of the woman’s pain. Muscle palpation in the area was unremarkable, so it wasn’t like the anesthetic would numb up active trigger points that were the source of the pain.

So I reclined the chair as I was telling her about the test I was going to do. I applied some topical anesthetic and told her we’d wait a little for that to take effect before I used the real stuff. After about a minute of letting the topical soak in, my patient looked at me and said that her chronic ache was gone. Hmm. Confused was I. But not my supervisor. Off to the neurologist our patient went.

Patients will often present with toothaches that they can’t localize to a particular tooth, or even point at a tooth that has nothing obviously wrong with it, and the responsibility falls on the dentist to diagnose the problem and treat the correct tooth.

Anaesthetic testing is most useful for eliminating quadrants as suspects rather than adjacent teeth (obviously). This however, can be a valuable tool, because referred tooth pain often does cross the horizontal midline.

Explanation by way of example:

A friend, K, called the office in tons of pain about 3 weeks ago. They were actually at their regular dentist and the dentist was pointing at 16 as the source of pain. K agreed.

I had seen her for the 16 about a year ago because of some pulpitic-type sensitivity she was having there. The problem turned out to be deep caries. I did some caries control and ended up with a pin-point vital pulpal exposure. I decided to pulp cap with MTA and see how things went. I also told her to have 48 extracted because it was partially erupted and picking up caries on the distal.

Everything settled after about a week.

With the phone call from the other office, it made sense that any current toothache had 16 as the likely source. My personal schedule (getting ready for the ProAm) didn’t allow me to see K quickly. Antibiotics and anti-inflammatories were of little help.

We managed to finally get K into the office. She hadn’t been sleeping well for about 3 days at that point. Again, she pointed at the 16, but said that the pain was pretty much on her whole right side at the back. Xrays of both upper and lower quads showed no areas consistent with apical pathosis. Because I figured we were dealing with an acute pulpitis, I didn’t want to torture K by cold testing the 16, but out of habit and instinct, I decided to test other teeth to try to definitively rule in 16 as the source of pain.

Cold testing was normal where it should have been except on 48. Cold applied to 48 provided some reduction in K’s overall pain level. Hmm. I decided to percussion-test the teeth. Both 47 and 48 were percussion sensitive relative to 16. Both 16 and 48 had been filled with resins by K’s dentist. Both fillings were falling apart.

So in comes the anaesthetic test. I gave 1/2 a cartridge of lidocaine as a buccal infiltration about 16. After 5 minutes, K indicated that she felt the pain still everywhere except for where I had given the freezing. The pain was practically the same intensity. This led me away from the 16 as the source, and to the 48 as the next likely candidate. A subsequent mandibular block eliminated the pain.

The problem turned out to be an irreversible pulpitis on 48. I didn’t go back and try cold-testing 16, but I’m assuming at this point that it’s pulpally ok…

When testing areas this way I usually start with inflitrations on top and save the lower block as the last injection. It’s much easier to control the field of anaesthesia on the upper arch than the lower. Field control is a good thing because the more we can isolate the anaesthesia to a particular tooth, the more information we glean from the test.