One of the most frustrating occurrences in endodontics is failure of LA. This can sometimes happen due to a technique failure, but there are also patients for whom LA is just not very effective. Difficulty in anaesthetising certain patients has been identified for as long as there is history in medicine and dentistry.
Probably the most common issue that we come across though is failure of anaesthesia when working with inflamed pulps. In these cases most of us will take any help we can get. One method of potentially improving our LA success is buffering of LA solution prior to injection. This process may reduce the pain felt on injection, reduce post-injection tissue injury and reduce the time to onset of LA.
There are a couple of theories behind buffering that may explain these effects. As you know, LA is an acidic solution, with those containing vasopressors being more acidic. Increasing the pH of the solution prior to injection allows more of the LA molecules to be in the lipid soluble de-ionised form (as opposed to the positive ionised form). This is the form that is capable of diffusing into the nerve, resulting in anaesthesia.
Another theory is that sodium bicarbonate mixed with LA interacts with hydrochloric acid to create water and carbon dioxide. The carbon dioxide may assert an independent anaesthetic effect, as well as potentiating the effect of the LA itself.
Stanley Malamed, one of the best-known names in dental LA reports on a small cross-over trial using buffered LA with adrenaline (epinephrine) with a mean reduction in LA onset from 7 minutes 29 seconds to 1 minute 51 seconds. Read the full article by Malamed here. Anecdotal evidence from practitioners who buffer their LA support this rapid onset effect.
So, how can we all get access to this. One options is to buy the Onpharma buffering pen, which I understand is a great product and easy to use, but expensive. The other option is to purchase 8.4% sodium bicarbonate and mix the solution chairside. Here’s a video from our friends at youtube on how to do this:
If you’ve been using the Onpharma pen, or have comments or opinions on buffering LA, please comment below and share the knowledge.
You can also read my post on LA complications here.