Lower Jaw take longer to respond to Novocain than Upper Jaw?!
Question:
Lower Jaw take longer to respond to Novocain than Upper Jaw?
I've had several cavities filled over the last few weeks. The first few were on the top of my mouth and the last few have been on the bottom. I felt NO pain whatsoever with the top fillings and I seemed to react very quickly to the local anesthetic or Novocain.
I’ve noticed that it takes an extremely long time to get numb on the bottom and have to have several shot of Novocain before I even feel ‘tingly’ Even after several shots I still seem to feel discomfort and pain. Is this normal? Is there a scientific explanation for this?
I’m worried because I’m getting a root canal done tonight….on the bottom.
Answers:
Well, since you asked for the scientific explanation, here it is:
(warning: dense technical details ahead!)
The lower jaw is harder to numb than the upper jaw, yes.
The upper jaw is easy to numb because its outer hard layer of bone is very thin, which means you can just inject in the gums near the tooth roots, and let the anesthetic diffuse past the thin layer of bone. That numbs up the tooth roots in the upper jaw nicely.
On the other hand, you can't do that on the lower jaw. The lower jawbone's outer hard layer is VERY thick. Anesthetic injected in the vicinity of the tooth will NOT diffuse in there to numb a tooth.
That means a different approach is needed to numb the lower jaw-- You have to give the injection towards the back of the jaw, where an entire nerve trunk enters the jawbone through an opening there. That's called the Inferior Alveolar Nerve Block (IANB) injection. When done right, the entire side of the jaw controlled by that one nerve trunk goes numb, all the way up to one side of your lower lip.
The IANB injection is not easy to do because the dentist has to guess where the nerve trunk goes into the bone-- The location of that opening is different in everyone. Sometimes it takes just 1 shot to hit it, sometimes it takes 4, sometimes it takes half an hour.
If you want to avoid pain in your lower jaw tooth while getting the root canal, you have to wait until half of your lower lip is numb. If it isn't, the root canal is going to hurt.
Hope this helps.