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.

 

Doc, That Short Hurt – Part II

In Part I of this series, I wrote about why some dental injections hurt while others do not. I approached this topic knowing that there were more than five factors affecting the amount of pain felt from the “shot at the dentist.” So here we go with five more reasons:

6. Size Matters?

Dental needle photo showing needles of different sizes

Wouldn’t you be more scared of the bigger one?

Many people – both dentists and patients – incorrectly assume that the larger the needle, the more painful the dental shot is going to be. While that may seem to be true, some well designed research studies contradict this.

What is true – and this is based on years of my own observations – is that when a patient sees a large needle coming at them – they are WAY more likely to complain that it hurt.

So, the last time you received a painful shot at the dentist, did you look at the needle? If yes, the sheer size may have “psyched you” in to thinking it was going to hurt! Perhaps the time it didn’t hurt was when the dentist and/or assistant distracted you so you didn’t see the needle.

7. Good Good Good Vibrations

It is unlikely that the Beach Boys were thinking of their trips to the dentist when they composed this famous song. However, when it comes to dental injections, vibrations are good.

Many dentists, myself included, will rapidly jiggle and wiggle the area we’re about to inject. Why? According to the Gate Control Theory of Pain, the intense stimulation of the wiggling will essentially prevent the pain of the needle. Stated another way, by wiggling the area so much, that wiggling “closes the gate” that the pain signals need to travel through. See the wikipedia article if you want more info.

Dentalvibe works by creating vibrations to prevent injection pain

The DentalVibe

I can promise you that if I give you an injection without doing any wiggling, you will feel it. However, if I apply techniques from Part I of this post and wiggle a lot, you will barely feel it!

Vibrating can make such a profound impact on whether you feel pain or not that there is even a product you can buy! It is called the DentalVibe and it is basically a professional wiggler. I have not used it but have seen it demonstrated at various dental conventions.

So, if you received a dental injection that hurt, it could be in part because your dentist did not wiggle the area (please note that in some circumstances it is not possible to wiggle).

8. Speed Kills

Many patients think that the most painful part of the injection is the initial pinch as the needle penetrates. In reality, there is another part that can also hurt: the forceful pushing of the fluid (the local anesthetic) into a confined area (the cheek or gums).

photo of teaspoon and tablespoon to depict amounts of dental local anesthetic

Imagine over 1/3rd of a teaspoon injected into you over 4 seconds. Ouch! (Image courtesy wiki commons)

So, what do you think happens when you receive an entire dental shot – 1.8 cc – approx 1/3rd of a teaspoon – into your mouth in under 5 seconds? It will hurt! That entry creates tremendous pressure on the tissue at the injection site, and that leads to pain. This study confirms this fact.

One of the key elements of a pain free injection is to go slowly. I try to do it very slowly – at least 30 seconds – sometimes as long as a minute. In nearly all cases, patients say “Doc, that took a long time, but I didn’t feel a thing!”

9. Local Anesthetic Buffering

This is distantly related to Point #5 –  Choice of Local Anesthetic. But it is different enough – and its impact large enough – to warrant its own entry. And this the buffering of the local anesthetic injection. But what the heck is a buffer?

lidocaine with epinephrine has a pH below 4

This comes at a pH of less than 4.

The pH, which is a measure of the acidity of your bloodstream and tissues, is approximately 7.4. In general, the closer the local anesthetic pH is to 7.4, the less it will sting during administration. One of the most common dental anesthetic formulations in the United States – 2% lidocaine with 1:100,000 epinephrine – has a pH of 3.85! Don’t you think that will sting?

Anutra Medical buffered local anesthetic

The Anutra Local Anesthetic Buffering System I use in my office.

One way to get around this is to buffer the local anesthetic. I won’t bore you with the chemistry but ask any high schooler who took AP Chemistry and he/she can explain it in more detail. But in essence, buffering will raise the pH close to your body’s normal pH. Do you think that an injection at a pH equal to that of your body will sting? No. And many research studies support this.

So why don’t all dentists use buffered local anesthetics? Well, it is not that easy. Local anesthetics cannot be manufactured this way because they would break down with 24-48 hours. However, a new product on the market called Anutra Medical allows dentists to do just this. It has not been widely adopted yet because it is new, requires special supplies be kept in stock, and is also slightly more expensive compared to traditional injections.

Having used the product, I can say with 100% certainty that it works. Patients feel less of the shot. It’s that simple.

10. Your attitude

This is the perhaps the most important factor but also the most difficult one to describe.

If you come in feeling nervous and anxious, act somewhat hostile to the dentist and/or assistant, complain that the topical anesthetic tastes bad, don’t want to open your mouth, stare at the needle as it comes towards you, move and jerk around as the needle goes in, then the injection will hurt. I’ve had patients where I’ve employed nearly every point in this post – and it still hurt because they did not let me do my job.

If you come in nervous but allow yourself to be relaxed, keep an open mind about things, and allow us to use our techniques (super topical anesthetic, wiggling, buffering, etc.), then you will feel little to no pain on injection.

Now I realize that not all dentists are the same – and not all dentists actively seek out new products/techniques to reduce injection pain. But most do. And most will be happy to talk to you about how to reduce the pain of the injection.

Might there be a Part 3 of this series? Maybe. If you have ideas, techniques, or products, email me at nick@directionsindentistry.net and maybe I’ll come up with reasons 11 through 15!

Doc, That Shot Hurt – Part I

As a dentist in private practice, I probably administer local anesthetic about ten times a day. Or to state this in terms that patients like to use, I probably give about ten shots each day. Sometimes more, sometimes less.

Very often, my patient will say something like “Wow, I barely felt that! You’re good.” But other times, I’ll hear “Wow, that hurt! My last dentist didn’t hurt me like this!”

The degree to which you will feel the shot while in the dental chair is dependent upon a number of factors. In fact, there are so many factors that they will be spread across two blog posts. Here’s part 1:

1. Location, Location, Location!

roof of the mouth or palate shot photograph

Any injection on the palate will hurt!

Just as the real estate saying goes, location is probably the number one factor in determining how much, if at all, a dental injection will hurt.

It is universally agreed upon by both dentists and patients that the shot on the roof of the mouth (more formally known as a palatal injection) hurts the most. Why? First off, the type of gum tissue present does not allow for topical anesthetic to work effectively. Secondly, the tissue is so tight and firm that the local anesthetic fluid has literally nowhere to go – making it very painful as the fluid is pushed in.

Conversely, other areas, such as on the outside of an upper tooth, we can make almost painless. You would literally not even know the injection occurred. This, however, assumes other factors are taken into account (those factors are outlined here and in the next post).

2. Topical Anesthetic

topical anesthetic used for dental injections photo

Topical Anesthetic

Topical anesthetic, more frequently referred to as “numbing jelly,” will reduce the initial “pinch” of the injection.

How does it do it?

The jelly is actually an anesthetic – just a viscous form similar to what is injected. When applied to the inside of the mouth, it will numb the area in approximately 1 minute. By making the superficial layers numb, the initial sensation of the pinch of the needle is either eliminated or reduced.

Most dentists use standard topical anesthesia these days. Some dentists, myself included, will use a high powered version that is compounded at a local pharmacy. When used properly, this type can almost completely eliminate the sensation of the needle.

If your dentist does not use topical anestheisa, you should request it. It makes a BIG difference.

3. Temperature

thermometer photo showing temperature affects pain from dental shots

Temperature of the local anesthetic affects how much you feel it.

This should be very obvious. Dental anesthetic is typically at room temperature – approximately 68 degrees Fahrenheit – and your body temperature is approximately 98 degrees Fahrenheit. Don’t you think that the 30 degree difference in temperature will make the shot be more painful?

If you answered yes, you are correct. And many research studies have confirmed this. It can make such a difference that there are actually local anesthetic warmers that dentists can buy.

Having used warmers before, I can attest that they appear to make a difference in how much you feel. But again, this assumes all other techniques are being used.

4. Presence of an Infection

Occasionally, a patient will have a significant dental infection that requires treatment. In many of those cases, an injection needs to made directly into the infected site.

pericoronitis photo where the dental shot will hurt

An injection into this infected tooth – with pericoronitis – will hurt.

Infected tissue is already hypersensitive. And the patient is already extremely distressed. And in many cases, there is a buildup of pus which is causing an increase in pressure. So what happens when you inject 1.8 cc of a local anesthetic into the infected area? You feel pain. This is because of the hypersensitivity, the likely buildup of pus underneath, and the stress.

So, injections into infected areas will always hurt, no matter what I or any other dentist try to do.

5. Choice of Local Anesthetic

First off, we dentists no longer use novocaine. In the United States, there are many different type of local anesthetics available. These include lidocaine, articaine, mepivicaine, bupivicaine, and many others. Some come with epinephrine and some come without.

According to some research studies, the choice of local anesthetic can affect how much pain you feel. This is because of differences in pH (the acidity). In humans, the pH at the injection site is typically 7.4. Doesn’t it make sense that the closer the local anesthetic is to 7.4 the less pain you will feel?

Lidocaine local anesthetic used for dentist shots

Some research says lidocaine hurts more than other local anesthetics!

One local anesthetic, prilocaine (brand name Citanest), has a pH of between 6.0 and 7.0. Many other common local anesthetics have pHs of approximately 5.0. So it stands to reason that prilocaine will hurt less because its pH is much closer to our body’s normal pH.

Well, one study confirms this finding, while another study finds no difference in type of anesthetic.

You might be asking then, why don’t all dentists use prilocaine? Prilocaine does not last as long as other local anesthetics. And many dentists (myself included) feel it is not as effective in getting patients properly numb. So many dentists elect not to use it.

Believe it or not, there are 5 more reasons why some shots hurt more than others. Part II can be found here.

5 More Reasons You Can’t Get Numb at the Dentist

In my recent post titled 5 Reasons You Can’t Get Numb at the Dentist, I laid out five reasons why this phenomenon occurs. This was based on years of experience as well as my own research.

In writing that post, it became clear that there were more than five reasons to explain the “I couldn’t get numb” occurrence.  So here are five more reasons why some patients experience this difficulty.

6. You have a Hot Tooth

Flames representing a hot tooth

Hot Teeth are tough to get numb!

If you are in severe pain in a specific tooth, it can be much more challenging to get you numb. This phenomenon, known by dentists as a hot tooth, produces these challenges in a different way than having an infection (infection was Reason #1 in the the first post on this subject.)

So why does this happen? There are two major reasons. When the nerve of a tooth becomes inflamed (such as from a large cavity), the nerve actually changes and becomes more excitable. Stated another way, the nerves are much more easily stimulated, and thus way more local anesthetic is needed.

The other reason is that the cavity can also cause the nerve to develop even more “receptors.” While the specific details are not that important for this summary, it basically means that there are more nerves that need to be taken out by the local anesthetic.

The end result in these cases is that it can take several injections to get a hot tooth numb. And in rare cases, sometimes antibiotics and two days off are needed for the tooth to calm down enough to be properly anesthetized!

7. Your metabolism

The term metabolism is technically inaccurate. But it is the best term to describe that in some individuals, your vascular system removes the local anesthetic from the area of the tooth nerve much more quickly than in other individuals. This results in you being adequately numb for only a short period of time, or simply not being numb enough at all. In either case, you end up feeling pain during the dental procedure.

Modern dental anesthetics are primarily metabolized in the liver. So any dentist who says you are metabolizing the local anesthetic too quickly is technically incorrect. But that will be addressed in another blog post.

8. I just used expired local anesthetic!

Dental lidocaine photo about to expire

Box and carpule of lidocaine. Yes, it can expire!

I can personally vouch that this has never happened to me. My assistants and I check the expiration date of each and every cartridge before injection. However, local anesthetic can and will expire. The average shelf life of local anesthetic is 12 to 18 months.

What happens if it expires? I really don’t know – but like any expired medication, it will likely begin to break down and result in a decrease in efficacy.

9. I missed

In many cases, in order to achieve adequate numbness, a dentist has to do a nerve block.

Femoral nerve block with an ultrasound

Ultrasound guided nerve block. Courtesy wikipedia.

Nerve blocks are not unique to dentistry. The photo to the left shows a femoral nerve block being performed by an anesthesiologist. In this case, the anesthesiologist is using an ultrasound to help guide the needle. This is done because inserting the needle and guiding it to the nerve is difficult.

Dentists do not have the luxury of using an ultrasound. Nor is it practical. For many nerve blocks, we have to insert a needle one and a half inches deep and rely on several anatomic indicators to help guide us.

Ted Williams was the last baseball hitter to hit above .400. That means 60% of the time, he didn’t get a hit. Most dentists have a batting average of around .900 for nerve blocks. So that means, just like Ted Williams, we sometime  swing and miss! So we have to inject again. And sometimes again. It’s part of doing nerve blocks… you don’t always hit a home run on the first at bat.

10. You’re Nervous

It is not a surprise that many people hate coming to the dentist. That it is a fact. Many people get very nervous coming to the dentist. That is a fact as well.

nervous people are tough to get numb

Dentistry is not a walk on the beach for most!

There is very little research to support my observation (and similar observations of other dentists) that patients who are very nervous tend to be more difficult to get numb.

Over the years, I’ve developed many theories for this. Many patients will forget to breathe and/or hold their breath. They may also clench their jaw muscles. Any of these will change the blood chemistry in a way that makes the local anesthetic less effective (similar to the blood chemistry changes I outlined in Point 1).

Since I do IV and Oral sedation dentistry, I’ve observed that patients who are sedated are much more easily numbed. This also suggests that nervousness and anxiety can make you more likely to experience pain.

The end result is that a nervous patient = a patient who may be difficult to get numb.

An eleventh and important reason – Ehlers Danlos – has its own post here

Do any patients or dental professionals reading this have other reasons? I have another list going but it is not at 5 yet. Leave a comment or email me at nick@directionsindentistry.net.