A Revolution in Dental LA Announced?

The Trans-Tasman Endodontic Conference was held in the beautiful New Zealand city of Christchurch on 4-6 November this year. It was great to catch up with good friends and see some interesting speakers. One of the headline acts was Dr Stanley Malamed, who is well known around the world for his books and lectures on emergency medicine in the dental surgery, local anaesthesia and sedation.

It was encouraging to hear Dr Malamed give support to many of the topics that were discussed in the previous blog post on how to prevent LA failure. He presented a lot of research supporting the increased efficacy of articaine when used in cases of acute pulpitis, especially when used as a buccal infiltration in addition to an inferior alveolar nerve block.

As with all conferences there are one or two things that catch your attention. One of those topics was presented by Dr Malamed and could be quite exciting if the research pans out as he expects. Essentially he was discussing a new way of accurately utilising a well known method of manipulating local anaesthetic to increase its efficacy. This could be a bit of a mini revelation in LA. Here is the theory:

LA is acidic. With adrenaline (epinephrine in US), a cartridge of LA is at about pH3.5. The lower the pH, the fewer molecules of the LA are in the active form which can penetrate the lipid membrane of the nerve and block the sodium gated channels. For lignocaine (lidocaine in US) with adrenaline at pH3.5, only 0.004% of the molecules are in the active form.

Raising the pH of the lignocaine to approximately 7.4 means that 24.03% of the local anesthetic ions are in the active form. This represents a 6000-fold increase. Buffering the LA solution by adding sodium bicarbonate just prior to injection can achieve this. The difficulty is in adding the correct amount of sodium bicarbonate to gain the correct effect. This is particularly difficult with cartridges such as those we use in dentistry.

Raising the pH also has benefits such as more comfortable injection (as the LA is not so acidic) and more rapid onset. Dr Malamed reported the results of a small preliminary study (double blinded randomized clinical trial in fact). Results were a significantly less painful injection with the buffered lignocaine and adrenaline, and an average onset time of 1 minute 26 for the buffered solution compared to 5 minutes 27 for the unbuffered solution.

This is exciting for all dentists! We need to see more studies on the efficacy of this buffered solution compared to other LA, especially articaine. But, anything that safely improves our ability to reliably anaesthetize teeth, especially those suffering from acute pulpitis is something worth watching in my book.

The product is called “Onset” I believe and should be available in 2011. It’s basically a machine that removes some of the LA from the cartridge and simultaneously injects an appropriate dose of sodium bicarbonate. Unfortunately it will only be available in the US initially, so the rest of us might have to wait a while. Hopefully this will give us time to see the results of further studies and assess whether the system works, and under what conditions.

The other invited speaker at the conference was Asgeir Sigurdsson. It was good to hear him talk also, especially since we’ve covered some topics that he has an interest in during previous podcasts. I’ll be updating you in what he had to say in a subsequent post.