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Monday, 14 May 2018

Why Do I Take A Long Time To Numb Up At The Dentist?

Dr. Vincent Wan


Is your mouth notoriously difficult to get numb?  Does the dentist have to give you double the amount of local anaesthetic to get you fully numb?  Even then, have you thought that you may still be feeling something in your tooth even though your lips and tongue feel numb and fat?

It is not all in your head.  Some patients’ mouths are simply not easy to numb up.  There are 3 main reasons for this:

  1. Complex Anatomy

Some patients have complex anatomy which makes it difficult for local anaesthetic to reach your nerves.  To numb up the teeth in the lower jaw, local anaesthetic must enter a small in the jaw bone next to the inside of your cheek.  If that small hole is particularly obscured by thick muscle, fatty tissue or mucosa, then you may not get much local anaesthetic numbing up your nerves.  If the hole is angled towards the back of the mouth, again not much local anaesthetic may get to the nerves.  There is usually one big nerve trunk, however some patients may have more than one nerve or multiple branches of the one nerve in the area where we are trying to numb.  One nerve or one nerve branch may be numbed, but other nerves or nerves branches may still provide sensation.

  1. Not Enough Anaesthetic

If not enough local anaesthetic can reach the nerves, then you may not have very profound numbness.  If this is the case, then another dose of the same type of local anaesthetic should provide profound numbness.  If you have profound numbness, you should feel numbness in the teeth, gums and surrounding soft tissues such as the cheek, lips and tongue and have little control over these tissues.

  1. Anaesthetic is Too Weak

If an extra dose still doesn’t give you profound numbness, then a different local anaesthetic may used.  Local anaesthetics work differently.  Two different types may provide much better numbness than a double dose of the same one.  Some local anaesthetics are extra heavy duty.  These may be used in difficult to numb cases, but they do take much longer to wear off.