Selective Anesthesia in Diagnosis

Diagnosis is perhaps the most critical step in the endodontic process.

We formulate our treatment plans, our patient discussions, and our expectations all from making the correct diagnosis. Simply stated, diagnosis is the basis of just about everything we do. But this is not always an easy task.

Of course we most often see the straight forward pain or infection conditions; the deep carious lesions, the radiographically obvious infections, or the traceable fistulas that are easy to determine. The challenging cases however require a much more involved approach to diagnosis. I want to simply use this blog to remind ourselves of one often overlooked clinical step in diagnosis: selective anesthesia.

I suspect we all use the standard tests in the diagnostic process. Evaluating the biting/chewing pressures towards a set of teeth lends significant information about ligamental inflammation and/or infection. Percussion and palpation tests offer a similar way to localize tenderness. Cold and hot tests give a measure of pulpal conditions. But there are many times when these tests do not add up to a clearly identifiable localization or a pain experience.

We deal with many grades of inflammation leading to differences in symptoms. For example, sometimes cold is the only provoking factor, sometimes cold offers relief of the pain, sometimes cold lingers and sometimes it doesn’t. And this is only the start of the ways cold can affect our teeth. Yet these 3 different reactions are all signs of pulpal inflammation of endodontic origin related to coldness, but with different interpretations based on the different grade of inflammation. Would it not just be easier if there was just one way a patient could interpret a cold response? Unfortunately that is far from reality.

We have to be knowledgeable about the brain’s interpretation of pain along a trigeminal neural pathway that supplies all our teeth. Radiating pain pathways often create challenges in diagnosis. I saw a patient recently who reported that yesterday she felt the pain on the bottom right. It was so strong it kept her awake at night. She arrived to our office the next day reporting the pain moved and is now distinctively on the top right (we ultimately found tooth #31 as the problem tooth). She was so certain of the pain coming from the top tooth that it took perhaps 5 minutes of discussion and ultimately giving her a nerve block to convince her of the true pain origin.

Additionally, we have to be aware of the intangible and subjective interpretation of pain by our patients. For example the reactions of one patient to a series of endodontic tests may be entirely exaggerated as compared to another more stoic and/or reserved patient. Any preconceived ideas of proper patient expression are useless. On a side note this is why we must test many teeth rather than just one tooth so as to gauge the individual response to testing methods.

Taking all this into consideration, there are a lot of challenges associated with proper diagnosis. Chapters and even books have been written on this subject. I will not attempt to regurgitate that information. Rather I just want to be a bird on the shoulder and remind all of us (myself included) that selective anesthesia can be a remarkable tool. It is easy and effective in many cases. But it does have some limitations.

Generally speaking pulpal inflammatory conditions will radiate pain much more than pulpal infection conditions which tend to be more of a localized experience. Thus in situations where a patient expresses they feel pain on an entire side of the face without specifically pointing to an upper or lower right area we can expect to be dealing most likely with a pulpal inflammatory condition. These cases you might expect to get a marked difference with a cold (or heat) test on one tooth vs. adjacent teeth to help formulate a diagnosis. But remember there are varying grades of pulpal inflammation and thus varying grades of cold interpretation. Ultimately the cold test might not give the specific localization of the problem tooth. The same can be stated for testing the ligamental inflammation by biting, or percussion exams.

It is not at all uncommon to evolve from the initial testing a suspicion of endodontic needs towards two teeth. I suspect I personally see this once every two weeks. Some of those cases actually involve teeth of opposing arches. Sometimes we will come across an upper tooth that expresses a clinically significant cold reaction, but no tenderness to biting/chewing/percussion. And the same patient will have a remarkable tenderness to biting/percussion to a tooth below it in the lower arch. This is just one example, but indeed there are so many variations of tests, patient responses, and expressions that can be described in a similar way. Personally I will look to provoke endodontically significant symptoms from at least 2 different tests to feel more confident in the pain origin. But a situation like this leaves some level of uncertainty. This uncertainty that can lead to improper diagnosis and improper treatment.

In situations like this we can use selective anesthesia to the maxilla or mandible to make a determination of pain localization. It does not really matter which arch you get numb. If the pain resolves instantly then you know the tooth in that arch is the problem tooth. If the pain remains then you know the culprit tooth is the opposite arch. This test can offer that sometimes needed help and confidence in determination the pain origin.

It does have some limitations though. For example we cannot predictably select anesthesia for adjacent teeth. Infiltration injections will affect adjacent teeth. Thus I cannot expect to get #5 numb without effects towards teeth #4 or #6. We might however be able to use the innervation of some roots to select between teeth separated by another tooth. For example I have had some unique situations where a patient present with deep decay of #15 and #12. I can recall a patient of this condition last year. He was having significant pain in the upper left side and while he ultimately needed RCT of both teeth (based on radiographic interpretation of deep decay) it was not clear which tooth was the primary pain source. He only had the finances to treat one tooth. Thus we needed to be right! Both teeth had elevated cold responses, and both teeth had mild tenderness to percussion and biting tests. Yes this might seem odd, and indeed it is. But we see all the odd things in our office when dealing with varying grades of pulpal/ligamental inflammation. The diagnostic testing was giving mixed results. I therefore gave a PSA (posterior superior alveolar) block knowing the nerve endings of this nerve do not reach #12. His pain persisted despite the anesthetic given. I treated #12 and his pain resolved. (He wished to wait for treatment of #15 in the New Year with renewed insurance which is why we did not treat both the same day).

Ultimately, the use of selective anesthetic while not an everyday tactic can be very helpful in finding the offending tooth and making the right diagnosis. As mentioned earlier, I feel this method is often forgotten about during a challenging diagnostic situation. But if you can remember to use it and if you can apply it to particular conditions, I suspect it will be a real advantage for you and of course for your patients who want their problem diagnosed and treated.

By Dr. Michael Brown

Thanks for visiting us at Tri City and Fallbrook Micro Endodontics of San Diego, CA.