The following is a review of available research on effective pain reducing tactics during local anesthesia injections.

Some of these are commonly used while others are not. Incorporating many or most of these ideas within our technique will take us one step closer to "zero pain" local anesthesia injections.

First it's important to understand what causes pain during the injection:

 

Needle

  • Needle penetration: Initial contact of the tip with the mucosa.

  • Needle movement: Movement of the tip to the target site after entering the mucosa.

  • Needle contact: Penetration/contact of the needle with muscle tissue or nerve fibers.


Solution


  • Solution volume: The pressure caused by the tissue volume.

  • Solution pH: Irritation/sting caused by the low pH of the solution.

  • Solution temperature: Room temperature is much lower than body temperature.


Review of the above list makes it obvious that a pain free injection would require that the technique used compensates for each of the above causes of pain and discomfort. The following is a list of pain reducing measures to take in order to ensure patient comfort:

1. Distraction:
Using calm comforting words and distracting patients' attention away from the injection needle is of course effective. Tapping or blowing air on a patient's hand, offering them dark glasses, and headphones with music are commonly advocated.

2. Needle gauge:
Research shows that using 25 gauge for blocks and 27 for infiltration is optimum; going any narrower does not reduce pain perception, in fact it is likely to cause more needle deflection and therefore adversely affect success.

3. Topical anesthetic:
This will help mitigate the pain of needle penetration through the mucosa. Opinion is divided about its effectiveness. Maxillary anterior sextant is most helped with the topical anesthetic; 20% benzocaine is commonly used. Anecdotal reports say EMLA and other pharmacologic formulations are even more effective.

4. Vibration:
Pinching, wriggling the lip or using specifically designed products [1] [2] to cause sufficient stimulation of the tissue being injected helps. This stimulates the larger A-fibers to inhibit the stimuli from smaller C-fibers conveying pain.

5. Two-step anesthesia:
A technique of injecting a few drops of anesthetic, waiting for few minutes and then returning to inject and complete the injection has been advocated. This method reduces the pain of needle penetration and movement because it is done in two separate steps. Though not practical for routine cases, it might be useful in some selective cases.

6. Slow speed:
Injecting at a speed of such that injecting one carpule would take about one minute; this puts the least trauma to the tissue and is shown to reduce pain.

7. Buffering anesthetic:
A Cochrane Systematic review [4] showed that buffering the anesthetic reduces pain. Proponents of this technique claim that this also speeds the onset of action, which would be an additional benefit.

8. Warming the capsule:
Systematic review studies [3] have shown that warming the anesthetic cartridge from a room temp of about 21°C to body temperature of about 37°C reduces the pain perception.

9. Technique:
This is especially critical for inferior alveolar blocks. The classic technique involves insertion of a needle into the pterygomandibular space by piercing the buccinator muscle. If the needle indeed traverses the ideal path it just pierces the mucosa and enters loose areolar tissue. Increased pain and discomfort is caused when the needle strays from the path to penetrate adjacent anatomical structures like the medial pterygoid muscle.

To keep the needle on an ideal path, it is necessary that the site and level of needle penetration and its angulation and depth is appropriate to the underlying anatomy of that patient. Anatomical variations like wide or flaring mandible, long ramus, endentulous mandible, can be best accommodated by using both intra-oral and extra-oral landmarks [5][6].

[1] Vibrajet [2] Dental Vibe
[3] Hogan ME, et al. Systematic review and meta-analysis of the effect of warming local anesthetics on injection pain. Ann Emerg Med. 2011
[4] Cepeda MS, et al. Adjusting the pH of lidocaine for reducing pain on injection. Cochrane Database Syst Rev. 2010
[5] Milles M. The missed inferior alveolar block: a new look at an old problem. Anesth Prog. 1984
[6] Khoury JN, et al. Applied anatomy of the pterygomandibular space: improving the success of inferior alveolar nerve blocks. Aust Dent J. 2011

Vivek Mehta DMD, FAGD, Visiting Faculty, Spear Education. Follow him on Twitter @Mehta_DMD.

 

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Comments

Commenter's Profile Image DR FARHAN DURRANI
May 30th, 2013
THE ABOVE MENTIONED CONCEPT OF PAIN FREE INJECTION LOOKS GOOD BUT HOW WILL THE CONTROL OF PSYCHOLOGICAL ASPECT OF COMING PAIN WILL BE MANAGED? ANYWAY I CONGRATULATE THE AUTHOR FOR ELABORATING IMPORTANT STEPS WHICH ARE VERY USEFUL IN DAILY PRACTISE
Commenter's Profile Image Dr.Susan Park
June 1st, 2013
I also have used the STA computerized anesthetic system for years with septocaine. What a pleasant difference it has made in my daily dental life and patients truly appreciate it.
Commenter's Profile Image Haynes Darlington
June 3rd, 2013
The ester molecule (Procaine) was abandoned due to allergic reactions. Why would one use a topical benzocaine (20%) with our current pharmacology knowledge? M. Pharm. D
Commenter's Profile Image Vivek Mehta
June 3rd, 2013
Dr. Darlington Thank you for your comment. Please help us understand what pharmacology reason makes benzocaine an undesirable choice. Your insights and opinion will take this conversation further. I could not find anything in my lit.search
Commenter's Profile Image Vivek Mehta
June 3rd, 2013
Dr.Susan Thank you for your comment. I am curious if you think STA is less painful for the patient because the speed of injection is very slow.
Commenter's Profile Image Vivek Mehta
June 3rd, 2013
Dr. Farhan D Thank you for the kind words. You raise a good point sometimes psychological management becomes crucial. It is a great topic for another post I think. I wonder if you have any favorite techniques
Commenter's Profile Image Mike Lindenberg
June 5th, 2013
Thanks to Dr. Mehta for this all important subject that not enough healthcare personnel pay attention to. All points made are clinically applicable and make a difference. I've never used the STM except at conferences, but definitely agree with the concept of a slow injection; in my opinion it is the difference maker. I have seen and been subjected to rapid injections and there is no excuse for it if you give a hoot. To Dr. Darlington, I used benzocaine topical for years without incident. I've never heard or seen a reaction personally or in the literature. Please elaborate if you would. Thanks
Commenter's Profile Image Todd Gruen
June 16th, 2013
Dr. Mehta, I have been using the STA as my primary mode of anaesthesia for 2 or 3 years now. Generally, I would say without hesitation that it seems to reduce patient discomfort. The biggest difference when it comes to infiltration would have to be slow, consistent delivery of the anaesthetic. The other variables are essentially the same as compared to a conventional syringe. Perhaps one other difference could be better "control", or "less movement" due to the design of the wand? Maybe. As far as using it intraligamentary, my experience leads me to the conclusion that generally this is a less uncomfortable injection as compared to an IAN block. This benefit changes however, when you are working on multiple lower teeth, as it would require multiple injections. To me, this is when an IAN block becomes indicated. Those are comments. My question is regarding buffered anaesthetic. We know that this changes the onset of action significantly. Is there any research or anecdotal evidence that it can compensate for blocks that would potentially "miss" without a buffering? Does it reduce the need for a second attempt, if you are not in the ideal spot? Thanks as always for sharing your knowledge!
Commenter's Profile Image Vivek Mehta
June 17th, 2013
Todd: Thank you for sharing your thoughts. I agree with your observations and conclusions on success with STA a.k.a. "wand" About buffered anestehtic - Does it improve the likelihood of success even if the injection has "missed the spot" - The short answer is no. For successful anesthesia adequate nerve length - about 8mm of nerve length (3 nodes of Ranvier) need to be blocked. So if I miss the nerve and deposit solution in a spot too far away, the faster diffusion capability of the buffered anesthetic is not going to help me. On the other hand, cases which are considered "failed" because the patient did not get numb in the first -10 minutes..... would now with buffered anesthetic be very likely be a success Patient response to anesthesia falls under typical bell curve - some get numb in first five minutes, most get numb in the next 5-10 minutes and there are few who take more than 15 minutes to get profound numbness. These late responders are sometimes categorized as failed anesthesia.
Commenter's Profile Image Pierre Comeau
June 20th, 2013
Do you have the best way to heat the anesthetic ? I like the Buffering idea, but it makes little economic sense. I heard that it costs 50$ per day to use it.
Commenter's Profile Image Vivek Mehta
June 22nd, 2013
Anesthetic warmer: This is the one that I know of - http://www.pattersondental.com/Supplies/ProductFamilyDetails/19760 Buffering: I agree about the expense - I hope more options come to the market. Having said that, Onset (http://www.onpharma.com) is a very user friendly, effective option
Commenter's Profile Image Kent Wilson
June 26th, 2013
Use 30 g for maxillary infiltrations, and 27 g for mand blocks: Smaller lumen slows flow=comfortable delivery. Warm syringe and carpule, and let topical sit for 2 minutes. Shake cheek and "apologize for the pressure..I wish there was another way.." Shows empathy, and helps a lot.
Commenter's Profile Image Kent Wilson
June 26th, 2013
Mix xylo and articaine in same syringe for mand blocks...very profound anesth every time.
Commenter's Profile Image Phan Ai Hung
July 10th, 2013
Please let me known how to post my result on this forum: "Pain and discomfort after intraoral injection of epinephrine-containing anesthetic solutions". It is a pdf file. Best regards
Commenter's Profile Image Tom Devlin
August 1st, 2013
Any comments or experience with any needleless injection systems? The Injex system is new and looks interesting as a sort of super topical that could at least numb the surface tissue so the actual injection with a wand or syringe would be felt less and eliminate the need for topical. If Dr. McCoy were a dentist what would he use?
Commenter's Profile Image Barry Musikant
September 21st, 2013
All written above is good. I do the following when giving IAN: First carpule is carbocaine. Less acidic and doesn't burn as much as xylocaine. The second injection is xylocaine, but the patient doesn't feel it. I use 30 gauge shorts. They hurt less than 25 or 27 gauge. I learned this technique after it was done on me and I was both surprised and delighted and asked the dentist who worked on me (Dr. Mark Docktor) what he did. Regards, Barry
Commenter's Profile Image Keren
January 21st, 2014
Here's another reliable article evaluating the effects of insulin jet-injections on insulin and glucose blood levels after a meal. http://medivizor.com/blog/SampleLibrary/diabetes-mellitus/needle-free-injections-improve-insulin-delivery/
Commenter's Profile Image Cynthia Brattesani
December 5th, 2014
I have used the STA\The Wand for over 18 years and my team can attest that patients are amazed how gentle the injection is for them. They often asked if I even used a needle! I do think the speed makes a huge difference plus they don't feel a cold syringe barrel on their lip that conjures up old memories. Another great advantage is that administering the injection is less taxing on the dentist's wrist. This allows you to consistitently administer a great injection even at the end of a long day!