Why do dental injections hurt? –
A patient receiving a dental injection.
One question that dental patients frequently (and understandably) have is: Will my injection hurt?
However, there are some basic factors and rules of thumb that can be used to give you a pretty good idea of what to expect. That’s what this page outlines and explains.
Why do some shots hurt and others not so much?
Location, location, location.
Anyone who’s had very much dental work done knows that the level of pain they’ll experience with any single injection can vary by quite a bit.
And even though most patients have their mind set on the needle as being the main culprit, the more important factor is the location (type of tissue) in which the shot is given. It’s this factor that explains why some injections end up hurting more than others.
The dental injection process.
Every shot is composed of 3 basic parts:
- The needle insertion. – This is the act of initially piercing the patient’s skin.
This step literally is just a pinprick. And even when it’s not totally painless, it only takes a split second to accomplish.
- Needle placement. – Once penetration through the skin has been made, the next step is for the dentist to advance the needle to the position where the anesthetic needs to be deposited.
There can be some discomfort associated with this process. But, as you’ll read below, the dentist has a simple way of minimizing what’s felt.
- Depositing (squirting out) the anesthetic solution. – This is the step that’s typically responsible for whatever amount of pain is felt. As a process, it involves the act of depositing the needed quantity of anesthetic solution into soft tissues.
The ease with which this is accomplished depends on the nature of the tissue itself. And this factor explains why the location where a shot is given is the biggest determinant of how much it’s going to hurt. (See below for more details.)
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The steps of the injection process – How a dentist gives a shot.
Here’s what a dentist does, or at least tries to accomplish, when they give an injection. Note that some of these steps are taken specifically to help to minimize the amount of pain you feel.
- Placing topical anesthetic. – This step precedes the actual injection. It involves placing a numbing agent on the surface of your skin where the shot will be given, in hopes that you won’t feel the prick of the needle as it’s inserted.
Unfortunately, this step really isn’t as effective as you’d expect. But that’s not to say that it doesn’t improve your experience. We explain what we mean in greater detail below.
- Needle insertion. – For this step, your dentist will stretch your skin taut (so it’s easily pierced) and advance the needle through it about 1/4th of an inch.
They’ll then express a few drops of anesthetic and pause for about 5 to 10 seconds as it takes effect.
- Needle placement. – Of course, the needle needs to be positioned properly before the bulk of the anesthetic can be deposited.
To get to this location, the dentist will advance it slowly, in small steps, while simultaneously expressing additional drops of anesthetic. This way the needle’s movement is always into tissue that’s already numb.
A dentist may deposit as much as 1/4th of the anesthetic in the syringe during the needle’s travels.
- Depositing the anesthetic. – Once the tip of the needle has reached its destination, the anesthetic solution can be placed. And as we explain why below, this is the process during which the greatest amount of pain is typically felt, if any is felt at all.
In short, the slower the rate of injection of the solution the less pain you’ll feel. A rate of about 1 ml per minute (or less) is usually considered optimal for minimizing discomfort.
Since the standard dosing held by a dental syringe is around 1.8 ml. This part of your dental injection will ideally (in terms of minimizing pain) last close to 2 minutes.
- The needle is withdrawn. – After the needle has been taken out, the anesthetic’s complete effect (including numbing your tooth) should take place within 3 to 5 minutes.
Did you notice these points?
The above steps include some interesting details that shouldn’t be overlooked.
- Did you notice that during the entire injection process (except the initial prick) that the needle is bathed in anesthetic solution? (The very medicine that makes it so tissues won’t respond to pain.)
- Doesn’t it seem counterintuitive that if you want a painless injection, you should want the whole process to take relatively longer (so the anesthetic is deposited more slowly)?
That suggests that giving your dentist your utmost cooperation will be to your benefit. After all, if you’re squirming and moaning their natural reaction will be to speed things up so the experience is over sooner for them too.
Why does the rate of injection correlate with the amount of pain felt?
It’s the physical act of depositing a quantity of liquid (the anesthetic) into tissues that has the greatest potential to cause injection discomfort.
That’s because the liquid itself has to find a location to occupy. And the more rapidly it’s expressed out of the dentist’s syringe, the larger the amount of disruption within the tissues it causes while doing this.
Additional factors involved.
Actually, beyond just the rate of injection, there are other factors that come into play too. They include:
- The total quantity (volume) of anesthetic that needs to be placed.
- The anesthetic’s permeability into tissues. (How quickly it’s absorbed.)
- How distensible (extendable) the surrounding tissues are.
The type of tissue involved matters too.
Actually, the rate of injection may not make much of a difference when an injection is made into “loose” tissues. But when “tight” ones are involved, the pinch of the solution as it forces its way into them may hurt quite a bit. And this fact alone is why shots in different locations have such varying potential to be painful.
a) “Loose” tissues.
The type of tissue in some locations is comparatively “loose” (freely movable), thus making it easy for the injected anesthetic to quickly find space to filter into and occupy.
‘Loose’ tissue examples.
As an example of “loose” oral tissue …
- Take your finger and place it on the side of your tooth.
- Then slide it (up on upper teeth, down on lowers) all of the way across the gum tissue until it stops.
- The soft, freely movable tissue your finger is now resting against is the depth of the “oral vestibule.” This is generally the location where shots are given into “loose” tissues.
b) Dense, firmly attached tissues.
In other areas, the nature of the tissue will be dense and tight. And as the anesthetic solution is deposited, it must forcibly make its own space.
It’s the pressure that builds up during this process that causes the pinching sensation you feel, and likely confuse with being caused by the needle itself.
‘Dense’ tissue examples.
Dense oral tissues are generally those that are firmly attached to the bone that lies underneath them.
This would include the gum tissue around your teeth as well as the tissue that covers your hard palate (roof of your mouth).
Research about injection pressures.
A number of studies have documented that slow, low-pressure injection technique is the key to performing painless dental shots (Primosch, Nagasawa, Kudo). That’s because it allows a maximum amount of time for the anesthetic to diffuse into the neighboring tissues.
In situations where the injection rate is too rapid, or the tissues involved are very dense, pressure is created as the anesthetic must force its way into the surrounding tissues. And it’s this tissue stretching and trauma that causes pain.
- Pashley calculated that the pressure of anesthetic exiting the needle during an injection could be as high as 330 to 660 psi in dense tissues (your car’s tires are inflated to around 32 psi).
In looser tissues, this value dropped on the order of 50 fold.
- Another study (Kudo) studied injection pressures (.6 to 9.5 psi) when shots were placed in loose oral tissues.
It determined that a pressure of just 6 psi (or less) was optimal for minimizing both pain and patient anxiety.
- A literature review of this subject conducted by Kwak states that reducing injection speed is the most effective method of reducing dental injection pain, while conceding that controlling and maintaining any specific (slow) speed of injection is difficult for clinicians.
As suggested by the points above, a big question is simply how does a dentist know how much injection pressure they’re creating?
Well of course, they don’t precisely. They just know to inject slowly. And if the patient seems to feel very much of what they’re doing, to go even slower.
An answer to this problem of technique can involve the use of a computer-controlled local anesthetic delivery system (CCLAD). Some of the brand names associated with these devices are: The Wand Single Tooth Anesthesia (STA) System, the Comfort Control Syringe (CCS), Quicksleeper, SleeperOne, iCT, Anaeject and Calaject. This type of device first became available to dentists in 1997.
- These units replace the use of a conventional dental syringe. (They are syringes in their own right.)
- They can be calibrated to deliver the anesthetic at a precise (slow) rate, thus minimizing the amount of solution pressure that’s created.
(However, unlike a dentist who while injecting manually might be able to vary (speed up) the rate of solution deposition according to what their patient can tolerate, the use of a CCLAD system generally requires a longer duration to complete the injection process.)
- What you do feel, exactly like when any other type of syringe is used, is the initial prick of the needle.
- What you may not feel as much is the process of the anesthetic being deposited (injected into the tissues).
Research studies involving controlled-delivery syringes.
When used with dense tissues (possibly the best application for these units), Nusstein determined that fewer patients felt pain (conventional dental syringe 43% vs. 25% when a Wand unit was used).
But not all research confirms that this high degree of difference when CCLAD systems are used. Studies by Asarch, Ram, Grace, Shah and a literature review by Wong each concluded that there were no significant differences in the patient’s experience/satisfaction when conventional or computer-assisted injections were given.
As a last reference, we’ll cite a recent literature review (Kwak) that evaluated 27 computer-controlled delivery system studies that had been conducted between the years 2000 and 2016. (The first of these systems, the Wand, was brought to market in 1997, so the date range involved encompasses essentially the entire history of the use of this technique.)
- The conclusions of the review seem to support the notion that the use of CCLAD systems is beneficial in reducing injection pain. But no collective statistical analysis or comparison was drawn from the studies evaluated.
- Interestingly, this paper also concluded that computer-controlled delivery systems were more effective when used with adults as opposed to children.
The explanation given for this point was that children tend to have a greater fear of the injection process in general, which in turn tends to affect their experience.
This suggests that any patient who has a high level of injection anxiety may not as fully benefit from the use of CCLAD technique until that issue is first controlled (see below).
Additional factors that may be responsible for injection pain.
The temperature of the anesthetic.
In an attempt to lessen their patients’ injection pain, some dentists pre-warm dental anesthetic cartridges before they’re used.
Schwartz suggests that the temperature of the injected anesthetic solution should lie somewhere between room and body temperature. And in fact, states that using cartridges that are too warm tends to increase injection discomfort. (Warming the solution helps it to penetrate into tissues more readily. (Liu))
Employing this technique may be of some benefit. But Davoudi states that the clinical trials documenting its efficacy are too few in numberto be conclusive. Even so, if you find that your dentist does go to the trouble of taking this step, at least they’re making a gesture toward making your injection less painful.
The pH of the anesthetic solution.
Generally speaking, the preparations that dentists use as local anesthetics are comparatively acidic in nature.
- Those that contain a vasopressor are the most acidic, usually having a pH in the range of 3.5.
Note: A vasopressor compound (usually epinephrine) helps to increase the duration of the local anesthetic’s effect.
- Even “plain” anesthetics (meaning those formulated without a vasopressor) are acidic in nature too, usually around pH 5.9.
- Neutral pH = 7.0.
The underlying problem.
The injection of lower pH (more acidic) solutions into tissues can be associated with:
- A sensation of burning or stinging during the injection process.
- The creation of soft tissue damage and associated post-injection soreness.
Interestingly, it’s only after the person’s tissues buffer the injected anesthetic closer to a pH of 7 that it begins to take effect. (This is one explanation why there is an “onset” period during which a shot begins to work.)
A possible solution.
All of the above suggests that if a dentist could buffer the pH of the anesthetic preparation to a pH of 7 before injecting it that it would make the injection process more pleasant for the patient and the effect of the shot would occur quicker.
A by Malamed involving 20 subjects seems to suggest this. It reported that:
- 72% of participants rated buffered injections more comfortable than unbuffered ones.
- 44% of the buffered injections were rated as painless by patients whereas only 6% of the unbuffered ones were.
- Buffered injections took effect on average in about 2 minutes whereas the unbuffered ones took over 7 minutes.
However, and specifically in regard to pain-reduction, another study (Comerci) reported no significant differences between the use of buffered and unbuffered anesthetics.
So, will your dental shot hurt?
Now that you know why injections can hurt, how do you know if yours will?
a) You’re probably going to feel the prick of the needle.
Your dentist can’t give you an injection without the needle piercing your skin. So you may feel that. But even if you do, the pain should only last a split second or so.
A review of dental literature by Nusstein concluded that 14 to 22% of people receiving mandibular block injections (see below) considered the initial prick of the needle to have caused moderate to severe pain.
What about using topical anesthetic?
In our outline above, the first step we mention involves the application of topical anesthetic. This product can be a gel, ointment, liquid, patch or spray.
Topical anesthetic gel.
It’s placed on your skin where the injection will be given in hope that you don’t feel the prick of the needle so much. After an application time of 1 to 2 minutes, topical anesthetics are typically effective to a depth of 2 to 3 mm (just a bit more than a 1/16th of an inch). (Schwartz)
The compounds most frequently used as topicals are: benzocaine, lidocaine, tetracaine and dyclonine hydrochloride. Flavoring is frequently added so to make them more palatable.
The truth of the matter is that placing a topical anesthetic isn’t as effective as most of us would hope.
- Nusstein, Meechan and Nakanishi each found that 20% benzocaine (probably the most used topical anesthetic) was not completely effective in controlling needle insertion pain.
- A study by Martin found that dental patients that thought they had received topical anesthetic prior to injection, whether they had or not, experienced the same level of discomfort.
Its use (real or placebo) did, however, lower the patient’s level of pre-injection anxiety. This suggests that the importance of topical application is more related to perceived rather than clinical effectiveness.
There are additional techniques that a dentist can use to minimize the discomfort of shots.
- Distraction – Whatever your dentist can do to distract you at the moment of injection can draw your attention away from focusing on how much it might hurt.
- Counterstimulation – Your dentist may create a pressure or vibratory sensation in the area where your injection is given. Nerve fiber transmission of vibration and touch sensations tends to inhibit pain transmission. (Davoudi)
Devices have been developed specifically for this purpose: DentaVibe, VibraJect, Accupal.
b) Other than the initial prick, you really may not feel very much discomfort.
We also described in our outline of the injection process …
- How the movement of the needle can be preceded by placing drops of anesthetic. (So the needle is always advancing into numbed tissue.)
- And how slowly depositing the anesthetic solution can help to control injection pain by minimizing the amount of pressure that’s created.
For these reasons, it’s quite possible that you really may not feel much, or even any, discomfort. Certainly many patients don’t. But it wouldn’t be right to suggest that all shots can always be painless, because that’s not accurate.
The fact of the matter is that some injections, due to the location in which they are given and the tissues they involve, often, even typically, do cause some level of discomfort. (That’s the subject of our next section.)
Which types of dental shots tend to be the most painful?
A study by Kaufman evaluated the pain response of patients when receiving some of the more frequently used types of dental injections used to numb up teeth.
Here they are, listed from least (1) to generally more painful (6), and our explanation of when each might be needed.
- local infiltration
- mental nerve block
- periodontal ligament injection
- maxillary incisor infiltration
- inferior alveolar nerve block
- palatal injections
i) Local infiltration.
If you’ve ever had a dental shot that was totally painless, to the point where you didn’t even know that anything was going on when you received it, it was probably one of these. The looseness of the tissue involved is why.
- This technique works with any upper tooth (see our comments below about upper incisors).
- On the lower jaw, it only works well with incisors.
What gets numb?
- The teeth and surrounding bone tissue in the area where the injection has been given.
- The soft tissues in this same area (however just on the side of the side of the tooth on which the injection was given, which is usually its cheek side).
With this technique, the anesthetic is placed directly adjacent to the tooth or tissues that require numbing.
The location of the injection is on the cheek side of the jaw (way up high with uppers or way down low with lowers) in tissues that are freely movable and “loose.” (That’s why this type of shot tends to be so painless.)
For this type of injection to work, the anesthetic solution must be able to filter through the bone (so to reach the area of the tooth’s nerve).
- The bone tissue of the upper jaw is relatively porous, which explains why this type of injection can be routinely used with upper teeth (see also “Maxillary Incisor Infiltration” below).
- Because the bone of the lower jaw is comparatively denser, the effectiveness of infiltration technique is less predictable (especially with back teeth) and therefore a “nerve block” injection is more likely to be used.
ii) Mental nerve block.
This is another type of shot that’s typically easy for a patient to receive.
Nerve “block” technique involves placing the anesthetic at a point along a nerve, beyond which its function is affected. The advantage of using a block is that several teeth as a group end up getting numb, not just the one or two in the immediate area of the injection.
With a Mental injection:
- The anesthetic is placed at that point where the Mental nerve (a branch of the Inferior Alveolar nerve) exits the jawbone through its foramen (tunnel-like opening on the surface of the jawbone).
- The area is then gently massaged so the solution enters into the foramen, thus numbing the Inferior Alveolar nerve at that point too.
- The injection blocks a total of two nerves.
- Due to this block’s effect on the Inferior Alveolar nerve, it can be used to numb up lower premolars (bicuspids), eyetooth (canine, cuspid), and incisors (on the side of the jaw the injection is given).
What gets numb?
- The teeth and surrounding bone tissue that are serviced by the Inferior Alveolar nerve from the point of the injection (area of the Mental foramen) forward to the midline of the jaw.
- The soft tissues (lip and gums) in this same region, but just on the lip side of the jaw (these are the structures serviced by the Mental nerve).
The Mental nerve’s access point for this technique is low down on the cheek side of the lower jaw, in the area of the tips of the roots of the premolars.
The tissue in this area is relatively “loose” (similar to that involved with infiltration injections describe above). For that reason, this is typically a relatively painless injection to receive.
iii Periodontal ligament injection.
Periodontal ligament (intraligamentary) injections are interesting shots, in the sense that they’re used to numb up precisely one tooth at a time.
The patient tends to feel the pressure of the process being performed, but often no pain. So whereas with the shots already discussed you may not realize much is going on, with this one it’s obvious.
- This type of shot can be used to numb any type of tooth, single or multi-rooted. And the onset of its effect can be rapid, if not immediate.
- It’s frequently used as an aid when other types of injections have not been totally effective.
What gets numb?
- Just the individual tooth around which the injection has been given.
- To some degree possibly the soft tissues immediately surrounding the tooth.
The injection is given (the needle is placed) directly into the space where a tooth and its gum tissue meet (the “sulcus”). It’s frequently given in more than one location around the tooth.
iv) Maxillary incisor infiltration.
If you’ve ever had a shot given for routine dental work on an upper front tooth and it brought an unexpected tear to your eye, it was probably one of these.
The way a dentist makes this shot painless is by placing a small amount of anesthetic initially. And then, after it’s taken effect, go back and deposit the rest of the needed dose.
- Upper central and lateral incisors are usually numbed up using this technique.
What gets numb?
- The teeth and surrounding bone tissue in the immediate area where the injection has been given.
- The soft tissues in this same area, however just on the lip side of the teeth.
This method is a type of local infiltration, just like the typically painless injection technique described above.
It’s given in the seemingly loose tissue directly above the upper incisors. Unfortunately, the area where the bulk of the anesthetic must be deposited is very tight and dense. And that’s why these shots pinch so much.
v) Inferior alveolar nerve block.
This injection, also referred to as a “mandibular block,” is used to numb lower teeth. If you’ve had much work done, it’s the shot that’s given in the rear-most portion of your mouth (behind all of your teeth) that ends up making the corner of your lip (on the same side) numb.
Most people take notice of getting one of these. Our source for this section ranked it as the most painful of the common dental injections. (We discuss pain levels associated with this type of shot below.)
- This injection is a type of nerve block (see above), and therefore has the advantage that it numbs several teeth simultaneously.
- The full potential and goal of this injection is to create a block of both the Inferior Alveolar and Lingual nerves.
- Any tooth on the lower jaw (on the side on which the injection was given) can be numbed using this method.
What gets numb?
When a block of both the Inferior Alveolar and Lingual nerves has been achieved:
- The teeth and bone tissue of the lower jaw (on the side the injection was given).
- The soft tissues covering that same side of the jaw, with the exception of those adjacent to and on the cheek side of the lower molars.
- One half of the tongue (on the side the injection was given).
The location for this shot is in the very back of the mouth, behind the lower molars.
The surface tissues in this location are relatively loose. But deeper down they’re tighter and denser, which makes depositing the anesthetic painlessly a challenge.
The needle placement required is fairly deep (about an inch). And that makes positioning it while creating a minimum amount of discomfort a challenge for the dentist too.
Above we discuss how the dense nature of the lower jaw’s bone makes using infiltration technique unpredictable (if not outright ineffective).
The idea associated with using a mandibular nerve block is that the anesthetic solution is placed at a point along the nerve where it just runs through soft tissues (has not yet entered into the jawbone).
vi) Palatal injections.
Our reference source for this section didn’t include palatal (roof of the mouth) injections because it only evaluated those used to numb up teeth. But Friedman ranks this type of shot as being more painful than any of those listed above.
- This type of injection isn’t used to numb up teeth, just gum tissue. And fortunately not that many procedures require it (gum surgery around upper teeth and some upper tooth extractions likely would).
What gets numb?
- The soft tissues in the area where the injection has been given.
- In some cases the injection is strategically given as a nerve block, thus producing a numbing effect beyond the local region where it has been given.
These shots are given in the roof of your mouth. Of course, the obvious problem is that the tissue in this region is very dense and tightly bound to the underlying bone.
As such, there’s very limited space for the anesthetic to diffuse into. And as a result, high injection pressures (and thus pain) are common.
Which type of shot will you get?
It’s probably safe to assume that whenever possible your dentist will give you the least painful type of shot possible. After all, why would they want your procedure to hurt more than it has to?
Having said that, there are other considerations they must weigh. The box below explains.
Factors in choosing injection type.
- Some types of shots typically create a more reliable or profound numbing effect than others. And so, what might suffice for a simple filling may not be effective for a tooth extraction.
- If one type of injection (such as a nerve block) will numb all of the teeth or tissue being worked with, whereas a possibly less painful method would need to be used for each individual location, using the former method may make more sense.
Fewer individual needle pricks would be needed. From a standpoint of possible medical complications, less anesthetic could be used too.
Research: How badly do mandibular blocks hurt?
In our list above, it’s the “inferior alveolar nerve block” (mandibular block) that’s singled out as the most painful of the routine injections used to numb up teeth.
van Wijk performed a study to determine exactly how much pain is felt when one of these injections is given. It evaluated 230 oral surgery patients.
- Roughly 20% of the patients expected their pain would be at a level of 7 to 10 (considered “substantial” pain by this study).
- After receiving their injection, only 3% of these same subjects reported actually feeling that much discomfort. (Expected pain intensity was higher than experienced pain.)
- 8% experienced discomfort at a level of 7 to 10 (“substantial” pain).
- The mean pain intensity was between 2 and 3 (“mild” pain).
- On average, the pain lasted for 5.3 seconds (with a range of 1 to 25 seconds).
- 36% of subjects felt pain for less than 2 seconds.
- 15% felt pain for more than 10 seconds.
The paper’s statement was: “A mandibular block injection can be considered to be a mildly painful experience lasting only a few seconds for the majority of patients.”
a) Size doesn’t matter.
There’s a common misconception among patients that the larger the needle that’s used, the more their shot will hurt.
Research doesn’t bear this out. There’s a long history of studies (Fuller, Brownbill, Flanagan, Malamed) that have evaluated the issue of the needle size used for an injection (30, 27 and 25 gauge, the common sizes used in dentistry) and the level of pain the dental patient feels. They have determined that the size of the needle makes no difference in what is felt.
Larger needles have advantages.
The size of the needle that your dentist uses is chosen for good reason, primarily dealing with safety (avoiding complications) and comfort. The box below explains.
Details about dental needle selection.
The needle that your dentist selects must …
- Be long enough and stiff enough (so it’s not deflected) to actually be able to reach the target area where the anesthetic must be deposited.
- Be long enough to retrieve if it breaks. And rigid enough that it’s not likely to. (Needles typically break off at their hub, the point where they attach to the syringe.)
Malamed reviewed published literature and determined that the incidence of breakage of 30 gauge needles (the smallest size routinely used in dentistry) was essentially 20 times higher than for 27 gauge ones (the “middle” size typically used).
Another advantage of larger needles is that they have a larger diameter lumen (the hollow tunnel within them).
- This helps to minimize injection pressure as the anesthetic is expressed (which helps to minimize pain).
- It also adds a safety factor in that it aids with accurate aspiration. (The dentist’s way of checking if the needle’s tip is positioned inside a blood vessel).
b) Needle sharpness.
A factor that may affect the amount of pain that’s felt is needle sharpness. Scanning electron microscope evaluation shows that after being used to give several shots, the point of a needle begins to blunt. This is true even if (hard) bone tissue is never contacted. (Rout)
A study by Meechan determined that using the same needle when giving a second injection in a second location resulted in a higher level of pain being felt. As a patient, during subsequent injections you may actually be able to notice that it’s more difficult for the needle to penetrate your skin.
c) Needle-free syringes / Jet injectors.
Needle-free dental syringes (like the Injex and Syrijet systems) have been developed for use in dental applications. They express a narrow high-pressure jet of anesthetic solution that’s able to penetrate through gum tissue “virtually painlessly.” They’re most predictably used for infiltration purposes only.
Even though this type of syringe has been available for decades, it hasn’t been widely adopted by dentists.
- Research seems to suggest that these injectors are neither quite as effective or substantially less painful than traditional methods (Davoudi, Wong).
- Additionally, the noise and pressure sensations they create can frighten patients. Their use may cause bruising at the point of injection.
▲ Section references – Wong, Davoudi
How the presence of infection affects a dentist’s use of local anesthetic.
As a part of their evaluation of your tooth, your dentist will need to formulate an opinion about the level of infection that exists in the tissues that surround it. Here’s why:
a) Local anesthetics are less effective in infected tissues.
Anesthetics are chemical compounds, and as such their molecular state is affected by the characteristics of the environment in which they’re placed.
- Ideal conditions for local anesthetic effectiveness is an environment of pH 7.4 (or above). This is physiologic pH, the level that normally prevails in the human body.
- At pH 7.4, 50% of a local anesthetic’s molecules will have a form that favors lipid-solubility, a characteristic that helps the molecule penetrate into nerve fibers and therefore have an effect on them.
By nature, infected tissues characteristically have a lower (more acidic) pH. And at these lower levels, a lower percentage of molecules will be in their lipid-soluble form, thus inhibiting the anesthetic’s effectiveness.
b) The injection process can spread infection.
Your dentist won’t want to do anything while performing your treatment that will cause additional complications. When infection is present, a potential trouble spot can involve the process of giving you your needed dental “shot.” Here’s why:
- When infection exists, the bacteria and byproducts associated with it will lie dispersed within the neighboring soft tissues.
- The act of giving a shot involves depositing a volume of liquid (the anesthetic).
- If the soft tissues receiving the solution contain components of the infection, as the liquid disperses it can carry them with it, thus enabling their spread into new areas.
▲ Section references – Singh
What is stated above generally applies to anesthetic placed using infiltration technique. Nerve block technique may avoid this complication if the point of nerve access is distant from the area of infection.
The tooth’s infection may need to be controlled first.
Your dentist will simply have to use their best judgment in determining how your current status affects their need to use an anesthetic, and vice versa.
They may decide that your tooth’s infection must be brought under control and allowed to subside before their treatment can be performed. Prescribing a regimen of oral antibiotics, typically over the course of about a week, is frequently used for this purpose.
Is there any way of having dental work done without getting a shot?
It’s conceivable that a person might possibly have their dental work performed without the use of a local anesthetic. Here are two possible scenarios:
a) Just not getting numbed up at all.
When it comes to pain avoidance, and as counterintuitive as it sounds, you might consider not being numbed up for your dental work. (Many dentists may not anticipate that this would even be a consideration for their patient. So if it is for you, you may need to bring this topic up yourself.)
A study by Tickle polled patients who had had fillings placed, some with the use of local anesthetic (dental shots) and others without.
The subjects who received anesthetic had a twofold increase in odds of reporting that their procedure was painful. The paper suggested that this discomfort was likely either associated with:
- The pain of the injections, which is often considered by patients the most unpleasant aspect of their treatment.
- Injection anxiety and its associated likelihood of emotional enhancement of pain perception when getting dental shots.
Will a no-anesthetic approach work with your case?
Not giving you a local anesthetic won’t be an option with all dental procedures. When this plan is applicable, it will probably just be with the most minor ones, like placing small fillings.
You’ll simply have to trust your dentist’s judgment about if trying this approach makes a good idea or not. And remember, they can always give you a shot later on if needed.
b) General anesthesia.
As a way of making their patient’s dental experience more pleasant for them, dentists often offer some type of sedation dentistry (see next section below). However, even when this approach is used (referred to as conscious sedation), a local anesthetic (getting a shot) is still needed for pain control.
As a step further, the use of general anesthesia might be considered. With this technique, the patient is placed in what’s essentially a medically induced coma. And while in that state, they are unable to feel pain and therefore a local anesthetic is not needed.
Does this make a good plan?
Possibly, but not usually. In fact, it’s rare that this approach is considered for routine dental procedures. Here’s why:
- The medicines involved typically need to be administered by an anesthesiologist, in a hospital setting where the needed monitoring equipment is available.
- There are very real health/medical risks and concerns involved with using this technique. It’s generally reserved for situations where other options aren’t available.
- The dentist must perform their work in a hospital setting and not in their office that’s been specifically equipped for this purpose.
Controlling the fear of getting dental injections.
There is no question that a patient’s mental state can affect their dental experience, including how much pain they feel.
- Okawa evaluated the relationship between patient anxiety and the level of discomfort they reported.
As you might expect, those displaying higher levels of anxiety experienced more pain with both their dental injections and procedure.
- van Wijk found that anxious patients reported experiencing more dental injection pain, over a longer duration.
If you’re interested in the subject, we have a page that discusses how quickly you can expect your dental shot to take effect. On average.
Page references sources:
Asarch T, et al. Efficacy of a computerized local anesthesia device in pediatric dentistry.
Becker DE, et al. Essentials of Local Anesthetic.
Brownbill JW, et al. Comparison of inferior dental nerve block injections in child patients using 30-gauge and 25-gauge short needles.
Comerci A, et al. Effect of a new local anesthetic buffering device on pain reduction during nerve block injections.
Davoudi A, et al. A brief review on the efficacy of different possible and nonpharmacological techniques in eliminating discomfort of local anesthesia injection during dental procedures.
Flanagan T, et al. Size doesn’t matter: needle gauge and injection pain.
Friedman MJ, et al. Using AMSA and P-ASA nerve blocks for aesthetic restorative dentistry.
Fuller NP, et al. Perception of pain to three different intraoral penetrations of needles.
Grace EG, et al. Computerized local dental anesthetic systems: patient and dentist satisfaction.
Kaufman E, et al. A Survey of Pain, Pressure, and Discomfort Induced by Commonly Used Oral Local Anesthesia Injections.
Kudo, M. Initial Injection Pressure for Dental Local Anesthesia: Effects on Pain and Anxiety.
Kwak E, et al. Computer-controlled local anesthetic delivery for painless anesthesia: a literature review.
Liu FC, et al. Effect of Warm Lidocaine on the Sensory Onset of Epidural Anesthesia: A Randomized Trial.
Malamed SF, et al. Needle breakage: incidence and prevention.
Malamed S. Buffering local anesthetics in dentistry.
Malamed S, et al. Faster onset and more comfortable injection with alkalinized 2% lidocaine with epinephrine 1:100,000.
Martin MD, et al. Topical anesthesia: differentiating the pharmacological and psychological contributions to efficacy.
Meechan JG, et al. Factors influencing the discomfort of intraoral needle penetration.
Meechan JG, et al. The use of patient controlled transcutaneous electronic nerve stimulation (TENS) to decrease the discomfort of regional anesthesia in dentistry: a randomized controlled clinical trial.
Nakanishi O, et al. Efficacy of mandibular topical anesthesia varies with the site of administration.
Nusstein J, et al. Effectiveness of 20% benzocaine as a topical anesthetic for intraoral injections.
Nusstein J, et al. Injection pain and postinjection pain of the anterior middle superior alveolar injection administered with the Wand or conventional syringe.
Okawa K, et al. Anxiety may enhance pain during dental treatment.
Pashley EL, et al. Pressures created by dental injections.
Primosch RE, et al. Influence of anesthetic flow rate delivered by the Wand Local Anesthetic System on pain response to palatal injections.
Ram D, et al. The assessment of pain sensation during local anesthesia using a computerized local anesthesia (Wand) and a conventional syringe.
Rout PG, et al. An investigation of the effect on 27 gauge needle tips following a single local anaesthetic injection.
Schwartz S. Local Anesthesia in Pediatric Dentistry.
Shah M, et al. A clinical comparison of pain perception and extent of area anesthetized by Wand and a traditional syringe.
Singh P. An emphasis on the wide usage and important role of local anesthesia in dentistry: A strategic review.
Tickle M, et al. Predictors of pain associated with routine procedures performed in general dental practice.
van Wijk AJ, et al. Pain related to mandibular block injections and its relationship with anxiety and previous experiences with dental anesthetics.
Wong JK. Adjuncts to Local Anesthesia: Separating fact from fiction.
All reference sources for topic Tooth Extractions.
Welcome to Animated Teeth.com and our page that discusses dental injections and factors that influence how much they hurt.
If you’ve had much dental work done, you may have noticed that some of the injections you’ve been given seemed to pinch quite a bit, and then others not really much at all.
Any dentist hearing this would agree that that sounds about right. They know that some injections have more potential to hurt than others. And if you’ve had enough work done, you’ve probably had a mix of both. So, what accounts for this variability? What makes some dental shots hurt more than others and when can you know what to expect?
Well, the factors that tend to make shots hurt are simple enough to understand. Our associated web page covers them in detail. This video takes highlights from that text.
For starters, there’s the issue of the needle and the fact that it must pierce the surface of your skin. On its own, this poke is literally a pinprick, which in other circumstances doesn’t seem to be such a big deal for most people. But since it precedes the remainder of the injection process and any expectations about what might be felt during it, for some this prick is a sign of worse to come and gets a big reaction. So, what can be done to get past this initial pinch?
The solution is to apply a topical anesthetic. It’s routine for a dentist to use a Q-tip applicator to smear flavored topical anesthetic gel in the location where they’ll give you your shot. And this step numbs your skin so it doesn’t register the initial prick of the needle.
Now, the reality of the situation is that this type of anesthetic only has the ability to numb your skin’s surface. So, only the initial prick is deadened. Once the needle has penetrated on in, a different set of nerve endings becomes involved. But at least the topical anesthetic gets you through the initial part of your shot.
So, now that the needle has penetrated your skin, what’s next? Well, obviously, the dentist must advance its tip to the location where the anesthetic needs to be placed to create its effect.
With upper teeth and lower front ones, that means positioning the end of the needle near the tip of the tooth’s roots. With lower back teeth, the target location is an area in the rear of your mouth where the nerve trunk that runs to your teeth can be accessed.
So, what can be done to minimize the pain caused by the needle as it travels through your tissues to the proper location? Well, what a dentist does is gently express drops of anesthetic as they simultaneously advance the needle forward. By doing so, they create a pathway of numbness ahead of where the needle will penetrate next.
Performing this process is why your dentist won’t rush to complete your shot. A slightly slower injection process gives more time for this plan to work, which of course is better for you. And remember, your dentist is only human, so make sure your behavior is such that it doesn’t make them want to rush.
Once the proper destination has been reached, depositing the anesthetic solution into your tissues can be another cause of pain.
Dental anesthetics come prepackaged in cartridges. They hold 1.8 milliliters of solution, which is about one-third of a teaspoon, or 36 drops from an eyedropper. So, when a shot is given, the location where the anesthetic is placed has to accommodate this amount of solution.
In the mouth, some locations characteristically have looser tissues and others comparatively tighter or denser ones. And this difference plays a role in what you feel.
With loose tissues, like where upper back teeth injections are given, as the dentist expresses the anesthetic out of the syringe, the surrounding tissues have a relatively easy time accommodating it. Minimal or no pain is felt because the extra volume of liquid is easily absorbed.
In the case of denser tissues, the anesthetic will disrupt and distend them as it creates space to occupy. It’s this process that causes the discomfort you feel, like when numbing up upper front teeth or the gum tissue on your palate.
In both instances, but especially with tighter tissues, there are some simple things that your dentist can do to help minimize the amount of discomfort you feel. For example, they may deposit a smaller volume of anesthetic initially. Then after that has numbed you up some, go back and give you the rest that’s needed.
Also, expressing the anesthetic from the syringe at a comparatively slower rate gives it more time to passively filter in. So, once again, and as counterintuitive as it seems, this is another reason why you don’t want your dentist to rush through the process of giving your shot. And why you need to give them as much cooperation as you can so they won’t be inclined to.
In passing, we’ll mention that the idea of needle size is sometimes a focus of attention for patients. With dental shots there are some issues associated with needle diameter and length that dictate what dimensions are considered necessary to perform certain injections safely. So, your dentist doesn’t necessarily have so much leeway in choosing.
As one last point, we’ll also mention that human psychology dictates that if you want your shot to hurt, it probably will.
Consider the situation where someone places a cup of cold water in front of you but tells you it’s hot. If there aren’t any telltale signs coming from the cup, when you first stick your finger in you’ll probably interpret the thermal shock you feel as being hot even though it’s not. That’s because your mind held a preconceived notion.
It can be the same with dental injections. If you’re certain it’s going to hurt, you’ll tend to slant your interpretation of events that way. So be as open to the experience as you can, and try to think positively.
With that, we’ll conclude this video. Remember, our web page contains a lot more details, so be sure to give it a read. Goodbye.
This section contains comments submitted in previous years. Many have been edited so to limit their scope to subjects discussed on this page.
Mandibular Block pain.
Is there a reason that a Manibular block injection might feel as if it’s burning halfway through the injection?
Our section on this page that discusses low pH anesthetics mentions that they can be associated with a burning sensation during injection. Possibly this is what you experienced.
On Lower Teeth Removal ,Will The Whole Tongue Be Numb Too?
A Mandibular block injection (Inferior Alveolar nerve block) is the most common injection used to numb up lower back teeth (molars, premolars). And the purpose of this injection includes numbing up the lingual nerve (the nerve that runs to the tongue, thus numbing it).
Lower canines and incisors can also be numbed up using a Mandibular block. But sometimes a different injection is chosen, one that doesn’t numb up the tongue.
The tongue itself is serviced by left and right lingual nerves. So if you’re only having teeth extracted on one side, only that side of the tongue will be numb.
A dentist will often be hesitant to extract teeth on both sides of the lower jaw during the same appointment (wisdom teeth seem to be a common exception). In this case, both sides of the jaw and tongue would be numb. This would be an awkward experience for the patient during the period following their procedure before their anesthesia has worn off. Good luck with your procedure.
My tongue is numb after 5 days after tooth extraction.
I went in for a tooth extraction on my left side the two back lower teeth molars the dentist procedure to give me an injection and slide my tongue on the left side and that was done this past Monday today it is Friday my tongue is still numb it’s causing me to be scared to eat because I’m scared to chew a hole in my tongue is this normal to still be numb
No, the prolonged numbness you notice is a treatment complication. Here’s a link to our page about dental paresthesia (which is what you’re experiencing). As it explains, the numbness might be a result of the injection or the extraction process. While most cases finally resolve on their own, you should report your condition to your dentist.
Ongoing pain at injection site.
I had a root canal done on a left bicuspid on Monday. As I was about to leave the office, I complained of significant pain. I was brought back and received a block, which I was told would be long acting…6 hours. I was numb for nearly 9 hrs.
Since then I have continued to have ongoing pain in the soft tissue below my gums where I believe I received the injections. It is very very sore to the touch, hurts to move my mouth, and has not improved at all since the procedure. I called the office & told them my concerns about the pain the day following. Was told I would be sore since I received a lot of anesthetic.
Now it is Thursday. Procedure was done on Monday and still no improvement in pain. The actual tooth needing treatment is fine. It’s in the area well below and behind the gum that hurts…. the area where injections are given. I take Advil and Tylenol multiple times a day. The pain does not go away. It’s constant, hurts when I touch and rub my jaw and when I move my mouth. What happened? I’m in tears over the unrelenting pain and lack of improvement. Thank you.
Jen is tired of…
An explanation could be that the injection process, the physical act of placing a volume of solution into soft tissues, has traumatized them. Especially if a muscle was involved, it would be sore to touch or when you move your jaw. Your dentist will have to investigate.
If that is the case, testing/stretching motions would tend to continue to aggravate the inflamed tissues. Taking Advil (an anti inflammatory medication) over the course of the episode would be therapeutic for the condition and help it to settle down faster. The use of Tylenol as a substitute would interfere with that treatment.
You should let your dentist’s office know that you are continuing to have problems with discomfort and let them make a recommendation about remedies or a solution.
Tooth freezing shoot to my head, is it normal?
Even though I never like needles, when it comes to my dental need, I tend to embrace with positive thoughts. I already had several fillings and a crown on my lower right last year from my dentist of over three decades and had no problem. Today I had an appointment for crown on my lower left tooth with a new dentist. The new dentist is very nice and it is not the issue. The issue is when he put a freezing needle, it took a long time and I felt it shoot to my head on left side. I felt dizzy for a short time, about one or two minutes. After that, I was fine. Freezing lasted about over four hours. Is it normal freezing shoot to head? I have never experienced like this before and want to ask. Please let me know.
I’m not going to have any definitive answer for you. Two fairly common events that sometimes occur, that seem somewhat reminiscence to what you state, are:
1) Sometimes the needle makes physical contact with the nerve being numbed up. Characteristically, that’s reported by the patient as feeling like an electrical shock. Usually it is felt in the tongue or lower lip, not the head. Possibly this type of incident might cause a prolonged numbing effect.
2) Sometimes, some of the anesthetic solution has been injected into a blood vessel. If so, the effects of the medication can cause cardiovascular and central nervous system events.
You’ll have to quiz your dentist about what they think occurred, since they’re the one who knows the circumstances of the event. Both of the above would be classified as random, relatively infrequent, events, with your dentist only having partial control over their avoidance.