How Long Does Novocaine Last?

One of the most common questions I see both in private practice and on this site relates to how long you will be numb after a dental procedure. In dentistry, there are a lot of factors that affect the duration, ranging from the type of the anesthetic to the location given, so there is no one correct answer.

In general, and this is a very broad generalization with many exceptions, you can expect to be numb for approximately 2 to 3 hours after you leave the office. Want to learn what factors affect how long you will be numb?

To use or not to use Epinephrine

lidocaine with epinephrine dental local anesthetic

Lidocaine with Epinephrine

Perhaps the most important factor that affects how long you will be numb is the presence (or absence) of epinephrine.

Epinephrine acts to constrict the blood vessels where the anesthetic is injected. By constricting the blood vessels, you have less blood flow in and out of the numbed-up area, and the local anesthetic does not get carried away from the teeth and nerves as quickly. As a result, you remain numb longer and the numbing sensation is much more profound.

Occasionally, some of the epinephrine can end up in the bloodstream, leading your heart to beat more rapidly and some other symptoms. Some people then mistakenly assume they are allergic to epinephrine which is impossible. See this MythBuster post and a follow-up article on why this is not possible.

If you receive an injection with an anesthetic without epinephrine, on average, you will be numb for about 1 hour or slightly less after you leave. This assumes your dentist uses one of the two most common: 3% carbocaine/mepivicaine or Citanest Plain/4% Prilocaine.

Type of Anesthetic

Besides the presence of epinephrine, the type of local anesthetic also plays a role. First off, novocaine is not used anymore, so I personally have no idea how long novocaine would last.

marcaine dental anesthetic will last a long time

This brand of dental local anesthetic can often last 8 hours.

Bupivacaine, which goes under the brand name Marcaine (at least in dentistry), can last a long time. In formulations without epinephrine, it can last 4 – 8 hours. When used in dentistry with epinephrine, it can last for 8 hours or more. In my experience, when I give bupivacaine with epinephrine for removing wisdom teeth, I tell patients that they can be numb until the next morning. Many of them report going to bed and still being numb.

Amount of Local Anesthetic Administered

Root canal procedure you need to be extremely numb

For a root canal, you typically need extra local anesthetic

This seems pretty obvious right? In general, the more you receive, the longer you’ll be numb. But remember that twice as much does not mean you will be numb twice as long. But you will be numb much longer.

For a straightforward filling, one shot (1.7 mL or cc) is typically sufficient, unless you are a patient who is difficult to get numb (see here and here on this phenomenon). For procedures that are a bit more involved, such as an extraction or root canal, dentists typically give more than one injection. The end result is you can often be numb for four or five hours afterwards.

Location, Location, Location!

Real estate is not the only area where this saying is relevant. The location – the area in the mouth where the local anesthetic is injected – plays a role in how long you will be numb.

a nerve block will last longer than other types of dental injections

A nerve block for a lower molar.

For a lower back tooth to be worked upon, you nearly always needs a nerve block. Nerve blocks last longer than infiltrations – which is when the anesthetic is placed directly next to the tooth.  In generalizing data from this paper, if you receive a nerve block, you will be numb approximately 25 to 30% longer than if you received an infiltration.

So what does all this mean? If you had a lower molar worked on, you were likely given a nerve block, and therefore you will likely be numb longer than if you received an injection for an upper front tooth.

Final Thoughts

This list is not exclusive. There are a lot of other factors – metabolism, genetics, hair color – but these four are the most common. I may do a follow-up post where I talk about the other factors. Comments are welcome.

 

Dentistry and Art: A Tooth Puller by Jan Steen

Jan Steen (b. 1626 d. 1679) was a Dutch painter known for painting daily life in the Netherlands in the 17th century. Just like today, people developed teeth problems (albeit more frequently back then), and thus dentistry was a part of everyday existence. Back then, there were no HIPAA laws nor sterilization protocols, so dentistry was frequently performed in public for all to see:

A Tooth Puller painting by Jan Steen showing a dentist

A Tooth Puller by Jan Steen, painted in 1651. Clicking on the photo will show a larger version.

The above work can be found in the Mauritshuis in The Hague, Netherlands.

You see the usual onlookers featured in nearly all paintings of this era. By the looks of it, this “dentist” appears to be a travelling one, going from village to village pulling teeth.

Nearly all dental paintings of that era show one thing: tooth extractions. Back then, there was no such thing as porcelain veneers, smile makeovers, or teeth whitening. Cocaine, the first local anesthetic (and what inspired novocaine), was still 200 years away from being used in dental procedures. If you had a problem back then, that meant only one thing: that tooth was going to come out and it was going to hurt!

Aren’t we all glad that dentistry has changed in the past 350 years or so?

 

More on the Fabled “Epinephrine Allergy”

Ever since I posted Dental MythBuster #10 – I’m Allergic to Epinephrine back in November 2013, I have observed its growing popularity. But much to my surprise, the “epinephrine allergy” post generated a tremendous number of comments and emails which attempted to refute my assertions and/or attack me personally. In fact, one email even threatened physical harm!

photo of epinephrine where people believe they are allergic

Many believe they are allergic to this.

I had no idea that I would strike such a nerve. Apparently, there are many individuals out there who are convinced they are allergic to a substance that has been running through their bloodstream since before they left their mother’s uterus. And they will stop at nothing to attack, ridicule, or even threaten anyone who might suggest otherwise.

While I generally attempt to stay away from the more controversial dental topics out there (like public water fluoridation or amalgam fillings containing mercury), I do feel compelled to publish additional facts and data to support the fact that an epinephrine allergy does not exist!

You Could be Reacting to Sulfites or Latex

Many individuals who claim to have an epinephrine allergy learn, either through an allergist or through my blog, that their post-injection symptoms were caused by either sensitivity or allergies to two components found in most dental injections: sulfite preservatives and/or latex.

Sulfites found in local anesthetics and red wine can give you allergic reactions.

Sulfites are found in most red wine and in local anesthetics containing epinephrine.

Sulfites are used to preserve epinephrine in dental anesthetics. Sulfites can provoke severe sensitivity reactions in certain individuals. If you receive a dental injection with sulfites and you are sensitive to it, the reaction can closely resemble an allergic type response (for in depth details on sulfites and dental local anesthetics, see this post I published).

On the tip of every dental local anesthetic carpule is a tiny piece of latex. Studies have shown that the latex allergen can enter into the local anesthetic solution when that latex is pierced for an injection. But those same studies also show no reports of an allergic reaction due to the latex. (Study info: Shojaei AR, Haas DA. Local anesthetic cartridges and latex allergy: a literature review. J Can Dent Assoc. 2002;68:622-626.)

I mention all this to demonstrate that there are at least two chemicals in the injection which could potentially cause an allergic type response. But it’s not the epinephrine!

It’s Documented in Textbooks and Articles

Many readers of my first post simply attacked me personally and stated that I was wrong. Others wanted proof. Here is a screen shot from an online article:

Article proving that an allergy to epinephrine does not exist

This screen shot is from this article in the magazine Dentistry Today. It says “allergy to epinephrine cannot occur.” It can’t get any more clear cut than with that statement!

Need more proof? In the book a Handbook of Local Anesthesia by Dr. Stanley Malamed, he writes:

Allergy to epinephrine cannot occur in a living person.

This is on page 320 from the 5th edition.

Why isn’t an Epinephrine Allergy Listed on the Drug Insert or Prescribing Information?

After tobacco companies, pharmaceutical firms are probably the biggest litigation targets out there. Haven’t we all seen ads on TV looking for plaintiffs to sue drug companies? Ever hear of the website 1800baddrug.com?

Naturally, drug companies list all the known adverse effects on the drug sheet. If they don’t list something, and then an event occurs, the attorneys will have a field day! So if an allergy to epinephrine existed, wouldn’t it be listed on the drug sheet?

penicillin lists an allergic reaction as a  risk

Unlike epinephrine, the insert for penicillin mentions the risk of allergy.

Look at the drug inserts for these common medications: Zithromax (Z-Pak), Penicillin, Bactrim

On all of these, you will see mentions of allergic reactions. This indicates that known allergies can occur after taking the medications.

Now look at the prescribing information for all these forms of epinephrine: Epinephrine Auto Injector, Epi-Pen, Epinephrine Injection.

None of them mention an allergy to epinephrine (note that some mention a reaction to the sulfite).

So I’ll pose the question again: if an allergy to epinephrine existed, wouldn’t it be listed on the drug sheet? Why would the drug companies fail to include it knowing they could potentially be sued over its exclusion?

Note that I’ve used the terms Drug Insert and Prescribing Information quite liberally here. There are many variations depending upon who it is for (consumer vs. prescriber), but it is the FDA-required document that pharmaceutical companies must publish.

Show us a Mechanism

If you’ve made it this far, and you’ve already read my first post, you’ve hopefully learned that an allergy to epinephrine is not possible. But for those determined skeptics, I’ll make this request:

Please provide a plausible mechanism for how you can be allergic to a chemical that has been in your bloodstream since before birth and is currently being synthesized and released in your body as you read this.

Should you wish to post comments on this article, I will ask politely that you refrain from profanity and/or personal attacks. And if you read this and your heart starts to race (either because you’re angry at me or you’re excited with what you learned), that’s because of the adrenaline being released into your bloodstream… to which you are not allergic!

What Does a Cavity Under a Crown Look Like?

As this blog approaches nearly 3 years of age and well over 150,000 views, I am able to see what the more popular dental topics are out there. Currently, the fourth most popular post on this site, clocking in with a little more than 19,000 views (as of July 2015), is Dental MythBuster #9: You can’t get a cavity under a crown.

In analyzing what people search for online, many readers – hundreds that is – searched for some variation of: what does a cavity under a dental crown look like?

I had just finished compiling this information when a long time patient of mine – one who I had been telling for several months now about decay under one of her crowns – called to finally schedule her extraction.

Photos and X-rays of Cavities Under a Crown

In this particular case, the decay was so deep that her only option was extraction (see below for why extraction was her only options). Below is a bitewing x-ray:

dental bitewing x-ray showing decay under a crown

The x-ray shows the definite shadow of decay underneath a crown.

I had first diagnosed this nearly a year ago primarily based on the x-ray. In this area of the mouth – the last tooth on the lower left – the cheek drapes up against the tooth – making it very difficult to see – and very difficult to brush!.

I then removed the tooth. And no, I did not put my knee on her chest! The decay was unmistakable. Upon completing the procedure and having the patient go home, the first thing I thought was: “this will make a great photo for my blog!” So here it is:

high quality detailed photo of extracted tooth with decayed cavity under a dental crown

The extracted tooth in all its glory. If you dare, you can click on it to see a larger version!

You can clearly see the decay on this crown when it is out of the mouth. However, when it was in her mouth, it was nearly impossible to see. It could only be “felt” with a dental instrument. But the x-ray showed it.

Why was the tooth extracted?

If you get decay underneath a crown, it doesn’t always mean that the tooth has to be extracted. Before I explain why this was extracted, let’s look at one where the tooth was able to be fixed:

high quality photo of a cavity under an incisor crown

The decay underneath this crown was predictably fixed with a new crown.

The tooth directly above could be saved because the decay was easily accessible and only extended slightly underneath the gum tissue. The tooth had already had a root canal.

For the first tooth, the decay extended deep underneath the gum tissue and went into the furcation (the furcation is where the two roots of two-rooted tooth meet). No amount of modern dental procedures could have saved the tooth. So we extracted it and placed a dental implant.

Please note that I have greatly simplified the criteria for when a tooth can be saved vs. extracted. There are dozens of other factors – all beyond the scope of this post.

So, to summarize:

  • You can get decay or cavities underneath a crown.
  • The extent and location of the decay as well as other factors will dictate the treatment needed to correct the problem.

As always, your dentist should answer all your questions. If he/she doesn’t, it’s time to look for a new one.