Australasian Dental Practice

Tuesday, 23 July, 2024

01 May 2005 | Australasian Dental Practice

news > Spectrum > Page 64

Malamed on mythbusting articaine, paraesthesia and neurotoxicity

World-renowned dental anaesthesia expert, Dr Stanley Malamed, has made a fleeting visit to Australia, delivering a combination of lectures and hands-on workshops in support of the newly available articaine 4% dental anaesthetic. Released in Australia by Septodont through local agents Henry Schein Region under their brand name of Septanest in February, Dr Malamed welcomed Australian dentists to the articaine club.

"I believe Australia is the 133rd country in the world to adopt the use of articaine as a local anaesthetic," Dr Malamed said, "In the majority of markets it is available in, it becomes the number one product within five years. In only four years, it has become the number two LA in the USA. In Germany, where it was developed and became available in 1975, it has 90% of the market.

"It's an interesting phenomena as even though there have been over 170 clinical trials on articaine since 1973, none show articaine is superior to any other drug. There is no evidence whatsoever. Nevertheless, the majority of dentists who try it, like it.

"The reasons for this are purely anecdotal but as I travel, I consistently hear the same comments. Articaine: 'Works faster'; 'Works better'; 'Is more profound'; 'You don't miss as often'; 'Works when and where other LAs don't'; 'Gets the palate numb when I infiltrate on the buccal'; and 'Gets mandibular molars numb following buccal infiltration'.

"Most, if not all of these statements are unsubstantiated scientifically, however wherever I speak throughout the world I continue to hear these same statements from doctors over and over again.

"Certainly what I have personally found with articaine is that where you have a patient that is hard to get numb - the one where you tell your assistant to load up three syringes - with those patients, you may get them numb with one cartridge of articaine and certainly less than you used before. If you are extracting an infected tooth and may in the past have needed 3, 4 or even 5 injections, articaine will do the same job with less. Articaine may be more expensive on a cartridge by cartridge basis, but overall you tend to use less to get the same result.

"Again, there are no clinical trials to support this, all the evidence is purely anecdotal, but there is enough of it to sell the product purely on word of mouth."

During his presentation, Dr Malamed explained the long history of dental anaesthesia since its development in the nineteenth century using drugs that included cocaine and later procaine, a synthesised version without the highly addictive properties of the former that was marketed under the well-known brand Novocaine.

He traced the progress that had been made from the early ester-based drugs with their inherent side effects through to the now popular amides. Articaine, an ester-amide hybrid, in essence is a further progression, delivering the most desirable properties of both.

"The amide-based anaesthetics - lidocaine, mepivacaine, prilocaine and bupivacaine - are all excellent local anaesthetics. They are very effective and provide profound anaesthesia and have done so since the 1940s. Local anaesthetics are the safest and most effective drugs in all of medicine for pain control."

Paraesthesia and neurotoxicity

Dr Malamed also addressed the ongoing debate regarding whether the use of 4% local anaesthetics were more likely to cause side effects including paraesthesia.

"Apart from loving using articaine, I've also heard another question from these same doctors: 'Should I use articaine for a mandibular block? I've heard that there is an increased risk of paraesthesia with 4% drugs.' As with my previously positive statements, there is absolutely no scientific proof that articaine, or prilocaine (the other 4% LA) are associated with increased risks of paraesthesia. All reports have been strictly anecdotal.

"Paraesthesia, defined as a prolonged anaesthesia, is a potential complication whenever a needle is inserted into tissue and a drug deposited near a nerve. All LAs can, and have, produced paraesthesia. Case reports of lidocaine, mepivacaine, prilocaine and articaine have appeared in the dental literature. Of late, however, it appears that an increasing number of case reports implicate articaine as a cause of paraesthesia.

"As a professor of anaesthesia at a US university, I have been intimately involved with the review of cases involving LA-associated paraesthesia. My feelings about this subject are, hopefully, unbiased. I mention this because I try very hard to evaluate each and every case that is presented to me to seek to determine which one or combination of the following might be responsible: (1) the needle, (2) haemorrhage, (3) edema, (4) surgical trauma, or (5) the LA drug.

"Most reports of paraesthesia involve the mandible, specifically the lingual nerve, either as a loss of sensation or on occasion, the loss of taste (the chorda tympani nerve). Frequently the paraesthesia also involves the inferior alveolar (IA) nerve, with associated paraesthesia of the chin, lip and buccal soft tissues in the anterior aspect of the mandible.

"Where an IA nerve block was administered and the paraesthesia involves only the lingual nerve, it is difficult to fault the LA drug (why wouldn't the IA nerve also be involved?). Many of these cases also involve reports of the patient experiencing a 'lightning bolt-like' feeling as the needle was advanced through their tissues.

"When LA is deposited against the lingual aspect of the mandibular ramus fibres of the IA nerve are blocked. When a paraesthesia develops in this situation and involves branches of the IA nerve, there is a greater possibility that the LA drug may be responsible, although the needle, haemorrhage and edema may still be possibilities."

According to Dr Malamed, "When a paraesthesia resolves over days to about two weeks, the likelihood is that it is a result of either edema or haemorrhage. More prolonged paraesthesia might be secondary to either needle trauma or neurotoxicity of the LA drug.

"The drug: anecdotal reports seem to indicate that there is a greater incidence in the chance of a paraesthesia with more highly concentrated LAs (4% / 3% / 2% / 0.5%). However, and it is important to realise, that there is absolutely no scientific evidence that this is the case. Haas reported in 1993 that the risk of paraesthesia following LA administration for all drugs was 1:786,000 injections. With 0.5%, 2% and 3% LAs the risk was 1:1.2 million. With 4% prilocaine the risk was 1:550,000 and articaine 4% was 1:440,000.

"However, his statistics were derived from voluntary reports of paraesthesia from Canadian dentists to their insurance carriers and estimates of the number of LA cartridges of each drug sold in Canada during a 21-year period. Additionally the nature of the dental procedure (surgery, conservative) was not known, nor was the length and gauge of the needle. Dr Anthony Pogrel, an oral and maxillofacial surgeon in the San Francisco Bay area has evaluated many patients with post-dentistry paraesthesia and states that the risk of a permanent inferior alveolar nerve paraesthesia is in the range of about 1:26,000. He further states that it is likely that during the practice career of every dentist, one patient will suffer a permanent paraesthesia following IA nerve block (independent of the drug administered). Pogrel states, and I concur, that the cause of the paraesthesia is usually unknown, that there is no way to prevent it (short of never administering a LA again) and there is no known treatment.

"At the end of the day, everything in dentistry must be assessed on a risk/return basis and there appears to be good reason why articaine has become as popular as it has."

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