Why does local anaesthetic not always work?

My regular dentist recently referred me to a colleague for some root canal work. The injection did not work. He didn't seem too concerned and told me it was because my tooth was infected and my body, in fighting the infection, was also removing the anaesthetic. Is this bullshit?





I've had many dentists. One used to regularly have to give me a second shot but in all other respects he was a very good dentist. I can only think of one more incident where I needed a second shot, which I didn't get on my last visit.

Why does local anaesthetic not always work?
Wow, a bunch of no minds sure were quick to answer you huh? The facts are twofold. One... when you have an infection, the area turns slightly acidic and this will neutralize the anesthetic. If the injection is placed into this area it will sometimes be neutralized to the point of not working. However, this can usually be overcome by placing a nerve block [hard to do on upper teeth though]. Two... if it was a lower tooth [where we normally do a block injection] it's possible to miss the nerve and cause a little hemorrhaging in the area which will neutralize the anesthetic no matter how much is injected. Most of the time [but not always], even if the anesthetic is neutralized, if the tooth can be opened, an injection directly into the pulp [nerve to you] will work
Reply:Dont tell me that...I have to go for treatment soon...always worked for me thankfully...sounds like B.S. to me.
Reply:your dentist is dum... i made sure my dentist injected 5 shots in all surrounding areas before he had my wisdom tooth pulled out, i had 4 removed and each time i made sure he gave me 4-5 shots even if he insisted 2 were enough... i mean come on i am the one whos going to feel the pain if you mess up the anestecia,right!
Reply:If the shot doesn't work, it's probly because they gave it to you in the wrong place. I know that's how epidurals work.
Reply:Usually this is because they do not hit a facial nerve. I have a very hard time getting the shots to work when I have work done. I have found another dentist that can use nitrous oxide so I do not have to go through this anymore. I have never heard of a dentist working on your teeth and there being an infection. That would be a signal that something is wrong here. If this were true, the infection could have spread throughout your body.
Reply:If you've had a lot of anaesthetic in your lifetime, your body can build up a resistance to it.


I remember having two injections in my big toe so I could have an in-growing toenail removed, the doctor said "You will feel a slight pulling." Yeah, right! It bloody hurt like hell!
Reply:Everybody's different. My dentist gives me four shots. Tell him you want gas also.
Reply:sounds like you should start brushing ya teath
Reply:Sorry to tell you this, but your dentist didn't know what he was talking about. The fact you being sick has no effect on the lidocaine that was probably used to numb your gums. Pain tolerance varies from person to person and is based on a number of different factors. Your immune system is not one of them.
Reply:I had the same problem.I dont know why,you could have an infection that interferes with the nerves or something.


I went to a holistic dentist last time %26amp; never felt a thing for 99%


of the time,that he was working on me.He used a herbal anaesthetic %26amp; I would be happy to have it again.
Reply:No, it's not bullshit. I'm a dental nurse and have seen it many times. Although dentists will often try to reduce the infection with antibiotics first before starting any treatment. Anaesthetic just won't take if there is infection present.