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Dentistry/2nd opinion - Root canal and lack of ability to get local anaesthesia


QUESTION: Dear Dr. Backlund,

Please pardon my interruption of your day, I was hoping for a very quick favor, even though you do not know me...

I had a temporary filling on a crown (tooth #18) for several months (with no pain or sensitivity), and I did a crown impression about one month ago. Last week, I went to my dentist, and they were supposed to set the permanent crown.

The problem was that the permanent crown did not fit properly, and they said they had to do another impression. So, they had to renumb me in order to do the impression. For some reason, they were unable to get me numb. Everything around my face was still numb, but I still had too much pain and sensitivity from blowing air, that they could not do the impression.

Thus, the dentist concluded that I would likely need a root canal. This was news to me, because I had no pain whatsoever prior to the first crown impression. I was wondering if you could give your opinion on two things:

1) Is the root canal truly necessary? (I have attached two X-rays)
2) Why was local anaesthesia unable to be achieved? (This scares me greatly).

Like I said, I am very worried and would be immensely grateful for a moment of your expertise. My appointment with the dentist is currently scheduled next week on Apr 15, but I am looking for second opinions.

Thank you!

ANSWER: Hi Sean,

I'm sorry all this is going on. I'll try to answer both parts of your question at the same time.... hopefully :-).

Since you have had no sensitivity or symptoms from that tooth and the only problem you have had was getting numb for the impression, that is just not typical of a tooth that needs a root canal. If you told me the tooth had been sensitive to hot & cold ever since the temporary was placed, then I might agree with your dentist. But just not being able to get you numb is really not a good diagnosis for doing a root canal in my opinion.

Sometimes on lower teeth all dentists have problems with getting the patient numb enough. It has to do with the location of the nerve and how close the dentist gets the anesthetic to that nerve. Sometimes there are also accessory nerves that come into play. It can be VERY frustrating for the dentist as well as the patient. Still not a good reason to do a root canal. Just because you had problems once getting numb does not mean there will be a problem the next time you need treatment. I assume,from what you wrote, that this is the 1st time you have had trouble getting numb. Before doing anything non-reversible, I would give it another try. You were obviously numb when the temporary was placed.

I hope this helps some and hope that all goes smoothly on the 15th.

Gary Backlund DMD, MSD

---------- FOLLOW-UP ----------

QUESTION: Dear Dr. Backlund,

Thank you for the quick response! This is helpful. I should clarify my situation, though.

The crown impression was the second one being done. My first crown had cracked (after a few years), and they put a filling or something in the crown which held it for a few months until I was able to get back to the dentist.

I had no pain or sensitivity in those few months, nor did I have any prior to the second crown impression (the one the replace the cracked one). And yes, I was able to get numb for it without a problem.

It was after the second crown impression that I woke up the next few days with a pretty severe headache, and then the sensitivity happened after the headache went away.

When they went to place the permanent crown in, for some reason the crown did not fit (I don't know why). So they said they'd need to do the impression again. That is when I was unable to get numb.

It was actually a very bizarre situation. They give me significant LA (not sure which caine), plus epinephrine. When it didn't seem to numb the tooth, one of the assistants said I should stand up and try to move around to make the anaesthetic work more quickly. When I stood up, I almost fainted, and my entire body went into sweats and they put me on an oxygen tank... It was not a good experience. I was left trying to figure out what went wrong that day, which was supposed to just be a simple cementing of a permanent crown... Which turned into (1) A bad fit, (2) an inability to get numb for the second impression (despite the rest of my face and eyes getting numb), (3) the possibility of root canal. Given I am already so dentalphobic, this isn't helping matters, but I am trying to do my best...

Were the Xrays I attached earlier not very useful? I was trying to figure out why those xrays were cropped so that the root is not attached. That is what the dental office gave me when I asked for Xrays. Is this a normal picture, or does it appear to have been cropped? I guess I've lost confidence and am searching for more answers.

Is it possible that something in the tooth was damaged during the  attempt at the crown impression? Would xrays before and after the impression help that? I am just confused and trying to get to the bottom of things.

Thank you once again, in advance!

ANSWER: Hi again Sean,

You're right, the x-rays don't show the end of the tooth. These are called bite wings and are designed to show decay or problems between the teeth, not at the ends. To show the ends requires a different type of x-ray, so these really aren't useful. In addition, x-rays only show problems when the nerve(pulp) of the tooth dies and there is a dark spot that forms at the end of the root. Your tooth is not dead or you would not be feeling temperature sensitivity which tells me your tooth is still alive. Unfortunately, in your situation, x-rays are really not helpful at all.

Like I said, I would just give it another go. Even if you were to select having a root canal, which I wouldn't advise at this point, you still need to be numb to do that procedure. So the goal here is to get your treatment completed and then see what happens. If you have continued problems with the tooth, you may need a root canal, and that can be done through the existing crown, so you won't be out any extra money.

Hope this explains things...

Gary Backlund DMD, MSD

---------- FOLLOW-UP ----------

QUESTION: Hi Dr. Backlund,

I went for an got another X-ray done at a different doctor and was wondering if you could tell anything more with this, relating to my case.

Thanks again for your time and quick thoughts.

Hi again Sean....

The x-ray appear completely normal. Like I said before, since the tooth was tender to air blowing on it, that tells me the tooth is still alive. The x-ray shows normal anatomy at the end of the tooth and no evidence of an abscess which is what I would expect when the tooth tests alive. Remember, even if you decide on a root canal, which I still don't advise, you need to be numb for that so getting you numb is still the issue...

Hope this helps.

Gary Backlund DMD, MSD  


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Gary Backlund, DMD, MSD


I am an Endodontist ( root canal specialist ) and can answer questions about root canals and their treatment. I cannot diagnose or treat online, but can answer general questions. I have been a specialist for 25 years and am Past President of the Washington State Association of Endodontists.


25 years practicing as a specialist

American Association of Endodonists, Past President Washington State Association of Endodontists.

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