Pain Free Dentistry: Local Anesthetics

One of the main reasons people hated and still loathe dentistry to some extent is because of the pain associated with it.

Thanks to the evolution of local anesthetics in dentistry you can be assured of a comfortable and pleasant experience during your visits.

As a dentist one of the most common questions I’m asked, as Im about to do any procedure is: Will it hurt? One thing not to forget is that you can let the dentist know when you are feeling pain. The dentist will stop and administer more anesthetic.

It is not our desire to torture you.

The use of anesthetic makes you more cooperative. This means that hopefully you will  follow our instructions better and we can efficiently finish the procedure in the shortest time possible.

So what is a local anesthetic?

A local anesthetic unlike its counterpart general anesthetic is the one most widely used in dentistry today. A local anesthetic only interrupts the sensation pathway or signals in the specific area in which the drug has been given. This means that only in the localized area of that nerve or nerve endings, will the effect of the anesthetic be felt.

General anesthetic is controlled unconsciousness and requires the presence of a licensed anesthesiologist. Most procedures in dentistry require your cooperation e.g  turning your head, rinsing your mouth, swallowing, biting down –  all things which you cannot do under general anesthesia. There are a few procedures however which are done under general anesthetic.   

The most common local anesthetics used in dentistry are from the amide group. I’m not going to give you a biochemistry and pharmacology lesson but it is important to know that rarely some people are allergic to anesthetics from the amide group and we may have to use other local anesthetics from the ester group.

Properties of local anesthetics

As a dentist what do I think about in my choice of local anesthetic?

Onset time – how quickly do you begin to feel its effects

Duration – how long will the effects last during and after a procedure

Potency – how much or what quantity do I have to use for you to feel its effects

While to you as a patient they all look the same in their cartridge -usually colorless liquids, we use different anesthetics depending on the different procedures.

Common local anesthetics


Lidocaine is the anesthetic most commonly used in most dental practices in North America.  Lidocaine is fast acting, which allows dentists to begin procedures quickly, one or two cartridges is enough for most routine dental procedures and it doesn’t cause an allergic reaction in most people.

You must think of lidocaine used in dentistry as being part of a twin set. Lidocaine will be prepared either with or without adrenaline. Adrenaline or epinephrine is used to achieve vasoconstriction. Think of it as temporary reduction in diameter of blood vessels.

Vasoconstriction can give additional benefits such as reduction in blood loss during procedures, decrease the amount of anesthetic needed while increasing its duration and limit the effects of the anesthetic in other areas. However there are certain medical conditions in which we do not use this combination of anesthetic with vasoconstrictor or administer it extremely carefully.

This is why we dentists must know about your general health. Individuals who suffer from uncontrolled hypertension, cardiovascular disease, uncontrolled hyperthyroidism and uncontrolled diabetes are not good candidates for the use of an anesthetic with a  vasoconstrictor.

I hope you’re beginning to get a better sense of the importance of general health to dental health and how it impacts our treatment protocols.


In Europe many countries may use articaine instead of lidocaine. Like lidocaine it is manufactured with or without adrenaline. Articaine’s molecular structure is different from lidocaine and because of this it has lower systemic intoxication. Both lidocaine and articaine have an intermediate duration of action.


The long acting local anesthetics are commonly used in lengthy procedures in dentistry such as endodontics, cyst removal, sinus lifting, etc. They are also used to manage  postoperative pain.

Bupivacaine is one such drug used when it is necessary to ensure that the effects will be long lasting since you don’t want the patient to start squirming or moving during delicate procedures. Anesthesia with bupivacaine can last up to 2 or 3 times longer than lidocaine or articaine.

An important question dentists usually ask during your first visit is: if you have ever had any adverse reactions to any dental anesthetic? It is vital that you answer this question truthfully because allergic reactions to local anesthetics may have dire consequences.

How is local anesthetic administered?


The hated image which is probably the most synonymous with dentistry. You need not fear. Dentists will not approach you with an upright needle while sending shots of anesthetics in the air. That’s for movies. 

Injection of Local Anesthetic
Injection of Local Anesthetic

A huge misconception even amongst dentists is that the needle diameter size will determine if you feel pain or not. Due to the fact that in dentistry needle diameter sizes don’t differ that widely, studies published have found that patients are not likely to perceive a difference in pain based on difference in needle diameter size.

What determines the amount of discomfort you may experience include;  the area of the mouth you are being injected in, the speed at which the injection is administered and most importantly the anesthetic itself.

Sometimes we may warm the cartridge of anesthetic in our hands or in a warmer before loading it into the syringe. Some studies have shown that warmer anesthetic being released into tissues is associated with less perceived pain by the patient.


This is applied to the skin or mucosa e.g. gums, but is only effective in interrupting sensation pathways in the most superficial layer of the mucosa approximately 2-3mm deep. In dentistry the two most commonly used are lidocaine and benzocaine. These can be in the form of gels, sprays or solutions and are used quite a bit in pediatric dentistry before local anesthesia injections.

Topical anesthetic is sometimes also used for root planing and or scaling, rubber dam clamp placement, placement of orthodontic bands and simple extraction of primary (milk) or deciduous teeth.  Topical anesthetics are extremely short acting but are more concentrated.

We further categorize injections of local anesthetics based on how large an area of the mouth we want to desensitize. If we want to desensitize only peripheral branches of a nerve or the main nerve trunk. That’s for another article because it depends on what procedure you’re getting done.

I hope this article has been helpful in allowing you to understand the tools we use to give you the best and most comfortable experience at your visit.

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