Local Anesthetics

Dental Anesthetic Epinephrine
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When you get a dental injection, your body wonders why on earth you’re allowing a sharp metal object to penetrate your gums!  It quickly tries to repair the damage by increasing blood flow to the area so it can carry away the anesthetic, which it views as a foreign substance. As you might have guessed, if your body’s protective response tries to get rid of all of the anesthetic, it’s not going to last very long.

Dental Anesthetic Epinephrine

This was a big problem with anesthetics back over 100 years ago.  Then, something exciting (to dentists anyway) happened!  A guy named Abel discovered adrenalin (a more common name for epinephrine) in 1897.   In 1903 Braun suggested using adrenalin as a “chemical tourniquet” to make anesthetics last for a longer period of time.

This Braun fellow recommended using epinephrine at the very small concentration of 1 part to 10,000.  That may seem weak, but we’ve found that even diluting it to 1 part to 200,000 still retains the beneficial effects of epinephrine while minimizing the side effects.

Epinephrine is what is known as a vasoconstrictor, which is just a fancy word for something that causes your blood vessels to constrict, or get smaller.

Why Dental Anesthetic Has Epinephrine

It is this vasoconstrictor effect of epinephrine that makes it so useful in dental anesthetic.  By constricting your blood vessels, it benefits you and your dentist in the following three ways.

1 – The anesthetic gets absorbed more slowly into your body because blood flow to the injection site is decreased.  Since blood levels of the local anesthetic are decreased, the risk of having an “overdose” of the dental anesthetic is minimized.

2 – Since there is less blood flow, the dental anesthetic stays put right around the nerve for a much longer time, allowing it to work for a longer period of time than it would without epinephrine.  This means that you stay comfortable throughout the entire procedure.  It also means that you might be numb for a few hours after leaving the dentist – a sometimes unwanted and embarrassing side effect!

3 – Minimizes bleeding where the anesthetic was administered.  This is great if the dentist is performing a more involved surgical procedure involving the gum tissue since it makes it much easier to see what we’re doing if there’s hardly any bleeding.

Epinephrine is the most common vasoconstrictor used in dental anesthetic in the United States.  In Europe, a vasoconstrictor called levonordefrine is commonly used.

If you prefer to not have these beneficial effects of epinephrine or if you have had heart problems, your dentist may elect to use a dental anesthetic without epinephrine. If that’s your preference and you want to seem like you know what you’re talking about, just ask your dentist for Carbocaine without epinephrine. That’s the most common brand name of dental anesthetic without any epinephrine.

If you have any questions about dental anesthetic and epinephrine, feel free to leave a comment below.  Thanks for reading!

Why Your Dentist Can't Get You Numb
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Did you know that over four million dental injections are given every year in the United States?  The failure rate is estimated to be anywhere from 5 to 15%.  that means that there are anywhere from 200,000 to 600,000 dental injections that don’t get the patient numb.  That means that people get poked by their dentist with a needle and don’t end up getting numb about every minute.

Dentist Getting Patient NumbIt’s no wonder that a lot of people come into my dental school and tell me something similar to, “My dentist has trouble getting me numb –  I usually need a lot of novocaine in order to get numb.”  As a side note, we normally use lidocaine, not novocaine as many patients believe.

So why do so many dental anesthetic injections not work – why can’t your dentist get you numb?

Seven Reasons Why Your Dentist Can’t Get You Numb

An article published in the January 1991 issue of the Journal of the American Dental Association sheds some insight into this issue by giving five reasons why dental injections sometimes don’t work.  I also found a couple of others and added them onto the list below.

1 – Anatomic Variations

Everyone is different.  Some people’s jaw flares out wider than others, making it hard to visualize where that person’s nerve is.  Some people have a longer jaw or extra muscle and/or fat around their jaw. In patients that are missing lots of teeth in the back of their mouth, it’s harder to visualize where the nerve is.  Also, young patients can have different anatomy depending on their stage of growth, making it hard to get the anesthetic in the right spot.

2 – Technical Errors by the Dentist

Dentists aren’t perfect!  Sometimes we can put the needle in the wrong place and give the anesthetic too low, too high, or too far to the side.  Also, we might not put the needle in deep enough, or we may accdentally deposit the anesthetic in a blood vessel, which is why your heart can beat fast when getting a dental injection.

3 – Anxious Patients

Some anxious patients may think that they aren’t numb and jerk away in fear when we start to drill.  In cases like this, I usually tap around their gums on the numb side and then on the side that isn’t numb to let them feel the difference and realize that they really are numb.

4 – Inflammation or Infection

When people have swelling in an area, it can be harder to get them numb.  One theory says that the acidic tissue makes it harder for the anesthetic to take effect.  Antoher theory says that since the patient has been in pain for so long, they have an increased sensitivity to pain which makes it harder for them to get numb.

5 – Defective Anesthetic Solutions

I haven’t had experience with this one, since my dental school has a pretty good quality control program to ensure that the dental anesthetic stays potent.  However, sometimes a dentist may use dental anesthetic that has expired or was improperly stored or manufactured.  This made me realize that I should always go with a respected brand name of dental anesthetic and not get the cheaper stuff to save money.  There’s no point in cutting corners if it will inconvenience my patients.

6 – Having Red Hair

People with red hair have more difficulty succumbing to the numbing effects of dental anesthetic.  They also have a greater fear of the dentist.

This article published in the July 2009 Journal of the American Dental Association states, “People with naturally red hair are resistant to subcutaneous local anesthetics and, therefore, may experience increased anxiety regarding dental care.”

7 – Having Joint Hypermobility

Those who suffer from Ehlers-Danlos Syndrome can be insensitive to local anesthetics used in dentistry.  You can check out this article for more information on local anesthetic failure in those with joint hypermobility.

Conclusion

If your dentist can’t get you numb, more than likely there is a specific reason.  In my experience, I’ve found that there are many people who have slightly different anatomy in their jaws which makes it harder to position the needle so that the anesthetic gets deposited where their nerve is located.

Do you have any questions, questions, comments, or concerns about getting numb at the dentist?  If so, feel free to go ahead and leave a comment below.  Thanks for reading!

Dental Anesthetic Makes Your Heart Beat Faster
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You may have noticed that when you get a dental injection, sometimes your heart feels like it’s going to beat right out of your chest.  You’ve probably just assumed that your heart is beating so hard because you’re nervous.

That’s partly true, but there’s another reason — the dental anesthetic actually contains something that makes your heart beat faster!

Why Your Heart Beats Faster When You Get a Dental Injection

Dental InjectionAs I mentioned above, nervousness may play a role in making your heart beat faster when you get a dental injection.  When we get nervous, our heart beats faster because our body sends out a substance called adrenaline that increases our blood pressure and causes our heart to race.

Most of the local anesthetics used in dentistry in the United States contain epinephrine (also known as adrenaline.)  Not only is your body causing your heart to speed up by releasing adrenaline, your dentist is giving you adrenaline in the local anesthetic!

Don’t worry, dentists don’t want you to have a double-dose of adrenaline to make you nervous.  Local anesthetics contain epinephrine for another reason: The epinephrine constricts your blood vessels.

With your blood vessels constricted, the local anesthetic stays near your tooth for a long time.  That way, it gives your dentist a lot of time to work on your tooth without you feeling it.  Another reason that dentists want your blood vessels constricted is so that only a small amount of local anesthetic gets absorbed into your body.

Conclusion

You may have felt your heart pounding more during some dental injections more than others.  If the dentist happens to inject the local anesthetic into a small blood vessel, it can quickly travel to your heart and cause it to beat very hard and fast.  This generally subsides after 10 seconds or so and is not dangerous to you.  Most of the time, the local anesthetic is not injected directly into a vessel and stays right near the nerve without affecting the heart.

Have you ever felt your heart race when getting a dental local anesthetic injection?  I’d love to hear your comments and questions in the comments section below.  Thanks for reading!

Update 2/25/13 – I wrote a new post about why dental anesthetic makes your heart beat faster, with more science to back it up after some comments below made me question whether or not this can really happen. You can read it here: Can Dental Anesthetic Really Make Your Heart Beat Faster?