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Dentistry/Numbing a tooth


QUESTION: Hi I went to my dentist today to be fitted for a crown.  I had a large filling in there and a few weeks ago it cracked on the one side.  My problem is he could not get the tooth numb.  I have never had this happen before.  It is the last lower molar.  He tried about 10 times and it got slightly numb but not numb enough to drill.  Every time he tried to drill the plain was intense and he had to stop.  He told me to come back in a few weeks and we would try again.  I use the anesthesia without the adrenaline because it really makes my heart race but I'm considering trying it again.  I don't know why he thinks it will work in a couple of weeks.  What do you think?

ANSWER: Hi Lynn,

I'm sorry to hear you had this experience. Unfortunately, it is not an uncommon occurrence. When we give shots to get the lower jaw numb, we give them way in the back to the place where the nerve comes out of the jaw, rather than right next to the tooth like when you get a shot for upper teeth. At can be difficult to get the needle in the exact location...often it is too high, too low, too long or too short so the anesthetic doesn't reach the nerve to get you numb. It seems that the more shots you get, the less likely you are to get numb...nobody can really explain that. In our office, we quit after 3 shots, but we use adrenaline whenever we can and that makes a "miss" even more difficult to get the patient numb on the next shot.

This happens to ALL dentists from time to time and is even complicated by the anatomy of some patients. We are aiming for an area about the size of a dime and in some patients, that place can be a bit different than most patients. This can cause some patients to have a VERY hard time getting numb on the lower and becomes frustrating for them as well as the dentist. Be thankful you are not one of these patients and this is just your first time this has happened.

You also asked why things would be better in a couple weeks. First, there is some trauma to the area from all the shots...that needs to heal some at least. Second, just giving things time will usually result in success the next time. It's exactly what we do when this happens in our office.

I realize I haven't given you a real scientific answer, but this is the best I can do. Most likely all will go just fine for you the next time.

Hope this helps.

Gary Backlund DMD, MSD

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

QUESTION: Thank you so much for your prompt reply.  I do feel sore from this experience.  Do they sometimes have to X-ray to find the correct spot?  As you can see I am worried about this but you have made me feel a lot better.

Hi again Lynn,

You are more than welcome. Glad I could help some anyway. Unfortunately, X-rays are really no help because they are a 2 dimensional picture of a 3 dimensional jaw, so locating "the spot" is still a bit of guessing, experience and using landmarks that are the same for most people. Since you have never had this trouble before, you are not one of those that has that "hole" in some weird place. I suspect next time all will go well.

Best regards,

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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