The Endospot Episode 1 | Preventing Local Anesthetic Failure in Endodontics

Problems with Local Anaesthesia?

In this, post, we discuss practical techniques for preventing failure of LA for endodontics, especially when dealing with irreversible pulpitis. Listren to the audio file below:

Preventing Local Anesthetic Failure in Endodontics

For the new and updated podcast, go to the podcast page.

References referred to in this podcast:

Meta Analyisis on Artciaine V lidocaine:
KATYAL V. 2010. The efficacy and safety of articaine versus lignocaine in dental treatments: A meta-analysis.  J dent: 38: 307-317

Intraossesous Injections:
READER A, NUSSTEIN J. 2002. Local anesthesia for endodontic pain. Endodontic Topics: 3: 14–30

Use of Articaine for buccal infiltration:
MATTHEWS R, DRUM M, READER A, NUSSTEIN J, BECK M. 2009. Articaine for Supplemental Buccal Mandibular Infiltration Anesthesia in Patients with Irreversible Pulpitis When the Inferior Alveolar Nerve Block Fails. J Endod: 35(3): 343-346
AGGARWAL V, JAIN A, KABI D. 2009. Anesthetic Efficacy of Supplemental Buccal and Lingual Infiltrations of Articaine and Lidocaine after an Inferior Alveolar Nerve Block in Patients with Irreversible Pulpitis. J Endod: 35(7). 925-929

PSA Block Link –
Information on the PSA Nerve:
Video: You Tube Video on the PSA Nerve Block

Show Transcript:
Welcome to the Endospot Episode 1.
In today’s podcast I’ll be discussing my techniques for managing local anaesthetic failure and specifically how to manage teeth diagnosed with irreversible pulpitis.

On the site we have references and show notes for this episode, so head to and remember you can sign up and receive the Endospot blog posts directly into your inbox.

So let’s get on with the podcast.

On the topic of failed LA, it’s important to recognise situations where complete anaesthesia is likely to be difficult to obtain. In general terms, the mandibular molar teeth are the most difficult to anaesthetise, and this is where you’re likely suffer the most failures.
The issue with mandibular molar teeth is compounded where we have an irreversible pulpitis. The inflamed pulp is always going to more difficult to anaesthetise. You’ll often have a slightly distressed patient in this situation, so it’s important to get it as right the first time. Once you’ve begun treatment on an anxious patient and they’ve suffered a level of pain due to failed LA, it can be quite difficult to win back their faith in you.

Now it’s certainly my experience that where the pulpitis has been long standing and is becoming more and more acute, this will be the most difficult tooth to get numb. A good example might be a case of cracked tooth syndrome where the tooth has been manageably painful to bite for months, but is now becoming more and more sensitive to thermal stimuli and spontaneous pain has begun to occur. I suggest you hit these ones with every trick in the book.

Abscessed teeth don’t normally represent a huge problem for anaesthesia in terms of being able to instrument the canals, but sometimes the surrounding tissues will be difficult to anesthetise and the patient will still respond to things like pressure. One caveat here though. Just because you’ve made a diagnosis of abscess, don’t assume that there is no vital tissue in the canal. Some vital tissue can remain in the canal even in the presence of pus and swelling, and attempting to debride this canal can result in high levels of pain. So, I always assume the worst when dealing with patients in pain and provide complete anaesthesia

In my previous last post, I covered the reasons for LA failure in pulpitis cases, so if you want more details and references, go to the blog post at and review those there. The main points that are worth considering though, are that a numb lip after IANB does not necessarily equal pulpal anaesthesia. This is the case even when dealing with an uninflamed pulp, but is especially so where you are dealing with an inflamed pulp. Research generally tells us that if we are dealing with an irreversible pulpitis and we give an IAN block which is apparently successful as the patient’s lip is numb, then , we’ll still only be successful in completely anaesthetising the tooth nerve about 55% of the time. Now, that’s obviously unacceptable, so we’re going to need to use supplementary LA for these cases.

The second point to note is that LA takes time to work. Again, research tells us that in 19-27% of cases, complete anaesthesia doesn’t occur until 15 minutes after the injection. So, next time your LA fails, it may simply be that the LA hasn’t had time to work. Supplemental techniques such as the PDL and intraosseous injection tend to work much faster than IADB, and should have you removing that inflamed pulp much faster.

As to which type of LA you should use, this will to a certain extent come down to personal preference, and obviously the medical profile of the patient. In general terms though, I would recommend using articaine. There’s been plenty of research in recent years devoted to articaine with some conflicting results. But, a recent meta-analysis concluded that articaine was more effective than lidocaine for anaesthetising mandibular molars. The article is by an Australian and so refers to lignocaine, but I assure you it’s the same drug.
So now I’ll go through my standard technique for dealing with hot pulps. Wherever not contraindicated, I’ll prescribe ibuprofen as soon as possible prior to treatment. There is some evidence that this alone may assist in achieving complete anaesthesia in inflamed pulps, but even if it doesn’t let’s remember that  these patients are presenting with pain, and therefore are at risk for post-operative pain. In this case, Ibuprofen (unless contraindicated) would be part of my pain management regime anyway.

When faced with a hot mandibular molar, I’ll start with a regular IAN Block and follow this with a buccal and lingual infiltration. The buccal infiltration ensures that a rubber dam clamp can be placed comfortably, but more importantly, I think that combining the block of the nerve with the local infiltration simply means that we have two sites along the nerve trunk that are blocked and this will lead to improved anaesthesia. This makes a lot of sense to me and is backed up by a number of studies which show that in cases of irreversible pulpitis, the infiltration significantly improves success rates. These studies have also shown the improved effect of articaine over lidocaine for this purpose.

After the buccal and lingual infiltrations, we take a minute’s break to ensure they are active and then move onto the PDL injection. There are a number of specialised equipment kits for PDL injections available, but they can be done successfully with a standard syringe. The first step is to bend the needle with some haemostats so that you are able to place pressure on the needle as it is forced into the PDL. The needle is inserted into the gingival crevice and with the bevel facing away from the root surface. Press hard and inject for 10s. There should be back pressure, if there isn’t, then the solutions wont’ be forced through the cribriform plate into the cancellous space and won’t be effective. I’ll perform the PDL injection at the four corners of the tooth.

The PDL injection is not really a PDL injection. I mentioned that the solution is forced into the cancellous space and as such It’s really an intraosseous injection. Therefore, there may be cardiovascular effects and this should be taken into account when selecting the LA. If an adrenaline containing LA is contraindicated, then you can use a non-adrenaline containing LA for this purpose.

The rate of onset of a PDL injection is fast, but the duration is short compared to IAN block, so at this point I’ll get a rubber dam on to the tooth and start access almost immediately. Once the pulp space is penetrated, and if vital tissue is found, then I’ll perform an intrapulpal injection. This injection relies on backpressure, so can only be used if only a small perforation is made into the pulp chamber.
For maxillary molars, I’ll start with a buccal and palatal infiltration, injecting most of the cartridge bucally. The palatal injection allows the rubber dam clamp to be placed comfortably, but might also anaesthetise the palatal root where a buccal infiltration could fail. After this, I perform a posterior superior alveolar block. I’ve placed a link in the show notes so you can have a look at this technique if you’re not familiar with it. I think that in the same way that the buccal infiltration in the mandible works with the IAN block to improve anaesthesia by blocking two points along the nerve trunk, combining a SPAN block with infiltrations should do the same. I then move onto PDL injections and perform an intrapulpal once the pulp chamber is entered.

The vast majority of cases, these procedures will allow you to enter the pulp space and remove most of the inflamed pulp tissue. If you are unable to even enter the pulp space, then your only real option is to perform an intraosseous injection. This does require specialised equipment. A good review of this technique can be found in the endodontic topics article referred to in the show notes. If you are comfortable with intraosseous injections, then these can be substituted for the PDL injections in the standard routine. My practical experience though is that if you follow the techniques described you really should have a very high level of success.

One point to note though is that infiltrations and PDL injections won’t make up for a failed IANB, so if there is any doubt that the block has been successful, then it’s worth repeating the block. If you want to be certain, it might make sense for you to perform the block and then wait until there are significant signs of lip and tongue anaesthesia before going onto the infiltrations and PDL injections. Obviously these injections can cause lip numbness also and so can mask a failed IAN block.

After entering the pulp chamber, you may find that you can remove some or most of the pulp tissue but attempting to pass a file to length in the canal elicits pain. In this case, I don’t see any reason to persist as the process of removing the bulk of the pulp tissue will result in resolution of the patient’s symptoms. I’ll dress the tooth with a corticosteroid containing dressing such as ledermix or odontopaste and send the patient home with assurances that the symptoms will resolve and the tooth will be easier to treat at the subsequent visit as the inflammation in the pulp will have resolved greatly. If you persist when complete anaesthesia isn’t achieved, you’re likely to put your patient and yourself through a lot of unnecessary pain, and the patient will be sure to be more anxious and will probably be one of those people that for the rest of their life tells their friends how agonising root canal treatment is.

So that is my routine for dealing with hot pulps. I’m aware there will be many different techniques out there and I’d love to hear some feedback. For those listeners who are just beginning their career, I’d recommend getting into the habit of using block and infiltration anaesthesia for all endodontic cases, and adding the PDL and intrapulpal injections when required.

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3 Responses to “The Endospot Episode 1 | Preventing Local Anesthetic Failure in Endodontics”

  1. Geoff Hill March 2, 2011 at 2:00 pm #

    I really enjoyed your lecture at BDSc last week! It was excellent!


  2. Dr. Ashim November 30, 2012 at 7:06 pm #

    Your info was real good. Can you please elaborate more on ladermix paste


  1. Whats New in LA @ the Trans Tasman Endodontic Conference | the endo spot - November 18, 2010

    […] 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 […]

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