Dental local anesthetics
Dental local anesthetics are the numbing agents dentist use to ensure local anesthesia of teeth and gums in order to do our work. There are several types of anesthetic we can use and several techniques from which we can choose to deliver it.
Dental local anesthetics options
Dental anesthetics are either amide or ester. Many contain the vasopressors epinephrine or levonordefrin and thus will have sodium metabisulfite preservative. Levonordefrin is a sympathomimetic amine we use as a vasoconstrictor and epinephrine restricts arteries in skin and tissue as part of it’s fight or flight response. Both vasopressors sting.
- Lidocaine – best for pregnancy
- Bupivicaine – causes inflammation so give some NSAIDs
Esters – this class creates PABA metabolite which can be a source of allergy
- Benzocaine – this can cause methemoglobinemia
The duration of action of a dental anesthetic varies due to
- Lipid solubility
- Protein binding – Better the binding the longer it acts
- Diffusion away from site
- Type of injection – blocks last longer than infiltration
- Tissue type – soft tissue lasts longer than pulpal.
Dental local anesthetic tips
Lidocaine – use 1:200k instead of 1:1ook since same effectiveness and less risk, use 1:50k for hemostasis. We consider lidocaine and prilocaine the safest local anesthetic for use during pregnancy.
Bupivicaine – only long lasting if block and in soft tissue NOT for pulpal if infiltration. Highest lipid solubility so can work at very low concentrations. Bupivacaine is the logical choice for longer procedures but it is on teh more painful side so give after soft tissue numb. Becker 2012
agents during injection
Mepivicaine – no epi last 20-40 pupal 2-3 h soft tissue. Lowest pKa so better for tissue with inflammation, infection, and re-injection. Shorter onset and longer duration than lidocaine. More effective IAN for teeth getting RCT with apical periodontists Visconti JOE 2016
Prilocaine is short acting, only lasts 40-60 pulpal if block and only 5-10 if infiltrate. It is the least painful during injection so some will use first. Prilocaine works well on hard to anesthetize patients. Rarely, one may encounter a patient with hereditary methemoglobinemia, which contraindicates the use of prilocaine. Becker 2012
Prilocaine w epi – similar lido and mep but since 4% higher toxicity so don’t bother except…….
Articaine – starts working a little faster and may be more profound. No difference for block or max infiltration but is for infiltration in mand (v lido) Kung JOE 2015
I have an entire blog post on the articaine v lidocaine argument.
Dental local anesthetics and their health risks
Methemoglobinemia will show clinically as blue lips and shortness of breath. It can result from benzocaine, prilocaine, and to a lesser extent lidocaine and possibly articaine.
TCA (Tricyclic antidepressants) and epinephrine can cause high blood pressure and heart rhythm issues. This seems to be pretty low risk in dentistry. Below is a partial list of TCAs.
- Amitriptyline or Elavil.
- Desipramine (Norpramin)
- Doxepin or Sinequan.
- Imipramine (Tofranil)
- Nortriptyline (Pamelor)
- Protriptyline (Vivactil)
- Trimipramine (Surmontil)
Non specific Beta blockers and epinephrine can cause a stroke, however, the doses we use are likely too low even if an inadvertent direct vein or artery injection occurs. Below is a list of non selective Beta blockers.
- Bucindolol (has additional α1-blocking activity)
- Carvedilol (has additional α1-blocking activity)
- Labetalol (has additional α1-blocking activity) or Trandate
- Nadolol or Corgard
- Oxprenolol (has intrinsic sympathomimetic activity)
- Penbutolol (has intrinsic sympathomimetic activity)
- Pindolol or Visken
Alpha blockers and phenothiazines can cause epinephrine reversal with results in vasodilation and we see short action of local anesthetic and more bleeding. If on these then we switch to levonordefrin anesthetic. Very unlikely to be on an alpha blocker.
Kovanaze is the only one on the market. It is 3% tetracaine and .05% oxymetazoline. It is only for upper anterior teeth and time on onset is long and it lasts a short amount of time. It is much less successful than traditional anesthetics, is less preferable, and has more side effects. Capetillo JOE 2019 Sounds GREAT!
Anesthetic half life
6x half live is what we consider gone from the body, which is why we see this term in use.
Dental local anesthetics by weight
This is a list of the common dental local anesthetics used in dentistry and how much can be used on a patient by weight. Most dental local anesthetics are about 2mg/lb. However, bupivicaine is about .5mg/lb which is why despite it being only .5% the number of carpules max is about the same as the 2% anesthetics. That works out to 1 carp of 2% dental anesthetic for every 20lbs. The formula % x20=mg/carpule is also useful.
Dental anesthetic injection techniques
Dental anesthetic injection techniques vary from dentist to dentist. I will cover a few studies on techniques in this section. An interesting study I ran across in JOE was on the impact of IAN injection and patient positioning. I was unaware that having the patient remain in the supine position results in slightly better success rates of anesthesia.
Wand vs traditional method
Dental local anesthetic injection injuries
We have an entire post on dental anesthetic nerve damage.
Having mandibular nerve block failures or difficulty getting a patient numb?
When the IAN block is successful but still does not produce sufficient anesthesia for the patient try
- Switch dental local anesthetic type, which is good advice for any failures not just blocks. Mepivicaine in particular is good for blocks and local if inflamed area.
- Lingual infiltration to anesthetize accessory innervation via the mylohyoid from the lingual
- Anesthetize retromolar area. 8%-75% have retromolar foramina with a retromolar nerve from the retromolar canal that may be accessory innervation from long buccal or IAN and/or a branch from the lingual nerve.
- In anterior cross the midline and place anesthetic
- Try switching to Gow-Gates (many feel this is superior from the get go). Also would likely get any bifurcated mandibular nerves which are thought to occur .1-.9% (pretty low really) and innervation from long buccal through the retromolar foramina.
- PDL and Intraosseous
- We have seen dentists recommending that a patient take 2-3 TUMs the night before and 2-3 TUMs an hour before the procedure. Can not find literature on that though.
Other issues for failure to anesthetize
Other major reasons that patients can not get numb that the dentist can not control are biochemical issues due to medical conditions or local factors and strange anatomy. Biochemical issues could be temporary, such as an infection in the area or desensitized nerves from drug use. The biochemical issues can also be from a medical condition or that individuals genetics.
There are anatomical reasons a block fails as well. Some patients will have some sensory innervation from the mylohyoid nerve. Some patients will have a bifuracted IAN resulting in a partially successful block.
Individuals with red hair are more difficult to get numb. Whether individuals with the MC1R gene simply have more anxiety, which makes it difficult to numb someone, or some other issue isn’t clear. Individuals with Ehlers Danos Syndrome are also more difficult to get numb. Research on individual genes and pain is ongoing, such as COMT. Phenotypes of the SCN10A play a role. Karataş JOE 2023
Injection location tips
No matter the tooth, injecting buccal and lingual will increase the probability of getting that tooth numb. Mandibular lateral incisors can go from 74% anesthetic success to 97% with a buccal and a lingual injection vs 2 buccal injections. Smithson JOE 2023
Dental injection methods.
AMSA for delivering denatl veneers.