There may actually be quite a few reasons why a dentist is unable to numb a patient’s mouth – Journal of the American Dental Association (1991).
Why dental injections may sometimes not work
1. Anatomic Variations – or everyone is a little different in understandable terms. Differences between people may include the following:
The jaw flares-out wider than others (making it harder for the dentist to visualize exactly where the nerve that needs numbing is), longer jaw bones or extra muscle and/or fat around the jaw, or people who have some missing back teeth are also reasons that may trick the dentist into think a nerve is in a certain place when it is actually in another.
Another consideration may include: the anatomy of a young person (stage of growth) – variable.
2. Dentist Errors – when considered that dentists are only human beings just like the rest of us (wrong placement of the injection [too far to the side, too deep, placed in a blood vessel], too low [high] a dose of anesthetic, or the dentist may just not be up to scratch).
3. Anxious Patients – may actually think that they are going to feel pain and that they are not numb enough (mind-over-matter can sometime result in a situation where the pain actually becomes a major issue and is more powerful that the anesthetic itself).
4. Inflammation or Infection – can affect how anesthetics work by making it more difficult to numb a given area in the mouth (acidic tissue is more difficult to numb due to the anesthetic not taking effect so easily). Also it is believed that when someone has suffered from pain for a long period, any increased sensitivity of pain becomes harder to numb.
5. Defective Anesthetic Solutions – may count for quite a few problems when numbness does not take effect (defective anesthetic that has expired, or improperly stored/manufactured anesthetics [brand names are always a better bet for dentists to use]).
Other reasons may include: having red hair (red-haired people are more resistant to subcutaneous local anesthetics – the American Dental Association [they also fear the dentist more]), and having Joint Hypermobility (sufferers of Ehlers-Danlos Syndrome are usually insensitive to dentistry local anesthetics).
Conclusion: By properly looking after one’s teeth (cleaning them after every meal [use floss at least twice a day], and have regular checkups) will promote good healthy strong teeth and offer the less chance that treatment may need to be carried-out, resulting in – numbing the mouth not being an issue.