IAN block in patient with an abcess

[Antz002]

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I'm having some trouble understanding something my supervisor said to me today. I asked her to explain herself, but her answer was unsatisfactory.

If a patient has an abcess on a 33, I understand that you cannot infiltrate due to the acidic nature of the infection, but I dont see why an inferior alveolar nerve block would not do the trick. Surely if you've cut off the pathway to the CNS substantially proximal to the infection, it doesnt matter whats going on distally?

Am I missing something, or is my supervisor losing it?

 

[DrJeff]

I'm having some trouble understanding something my supervisor said to me today. I asked her to explain herself, but her answer was unsatisfactory.

If a patient has an abcess on a 33, I understand that you cannot infiltrate due to the acidic nature of the infection, but I dont see why an inferior alveolar nerve block would not do the trick. Surely if you've cut off the pathway to the CNS substantially proximal to the infection, it doesnt matter whats going on distally?

Am I missing something, or is my supervisor losing it?

I'm guessing that you're talking tooth 3.3 - lower left canine. The biggest issue with IAB's and an abcess is the acid/base battle between the puss and the anesthetic, no if's and's or but's about it. Personally, with a tooth like that, I'd give the IAB, give a mental NB a PDL on that tooth, and then some buccal infiltration, and then get into that pulp space as quick as possible. Do I get everyone 100% numb that way, no (I don't think that any clinician would say that they do for a really "hot" tooth). But do I get good anesthesia on 80%+ of patients like that, yes, and maybe only 3 to 5% of those patients will I just not be able to get decent enough anesthesia that way to get access to the tooth and get them out of pain. Those few get antibiotics and pain medication and I reappoint then in 48-72 hours when hopefully the antibiotics will have helped shift the acid/base ratio enough in MY favor that I can take care of them comfortably

 

[Antz002]

Thanks DrJeff - I just read my original post and realised that I never mentioned that the supervisor said that an IANB would probably not work in this patient. (The lower left canine is correct by the way - I'm from South Africa where we use mainly FDI notation.) I understand the acid/base interaction between the local and the abcess, but what I dont get is why the IANB would not work. Perhaps my understanding of the mechanism of action of the LA is lacking?

If you have 'cut off' the pathway of impulse transmission to the brain sufficiently proximal to the abcess (ie. no acid/base neutralisation of LA), how can the patient still feel pain?

 

[armorshell]

Your intuition about the anatomy was correct - if you can anesthetize a sufficient length of the IA to prevent signal transmission proximal to the area you're going to traumatize, then you have achieved acceptable anesthesia.

Why this is such a mysterious concept to many, I will never understand. A local infective process will only affect your ability to achieve anesthesia if that process is localized to the area you're trying to deliver your anesthetic.

For example, if you were trying to deliver anesthesia locally (for soft tissue anesthesia, or a local infiltration for pulpal anesthesia, say in the maxilla), that would be less effective.

Anterior mandible is pretty easy to get numb despite infective processes since the whole region, soft and hard tissue, can easily be obtunded with distant nerve blocks. Posterior mandible and maxilla get tougher since an infective process is closer to the proximal nervous anatomy and your block injections are less commonly used. (IO/V2/V3)

 

[jay47]

Your intuition about the anatomy was correct - if you can anesthetize a sufficient length of the IA to prevent signal transmission proximal to the area you're going to traumatize, then you have achieved acceptable anesthesia.

Why this is such a mysterious concept to many, I will never understand. A local infective process will only affect your ability to achieve anesthesia if that process is localized to the area you're trying to deliver your anesthetic.

For example, if you were trying to deliver anesthesia locally (for soft tissue anesthesia, or a local infiltration for pulpal anesthesia, say in the maxilla), that would be less effective.

Anterior mandible is pretty easy to get numb despite infective processes since the whole region, soft and hard tissue, can easily be obtunded with distant nerve blocks. Posterior mandible and maxilla get tougher since an infective process is closer to the proximal nervous anatomy and your block injections are less commonly used. (IO/V2/V3)

The problem is that recent research (can't remember study- I'll find it later and cite it) has shown that the success of the IAN decreases as you move anteriorly within the mandible. This is due to the proposed innervation scheme of the IAN. The most distal teeth have fibers running in the outer portion of the nerve, most of which receive adequate local anesthetic from the block. However, deeper within the nerve, the fibers running to the premolars and incisors do not receive an adequate amount of local anesthetic.

In addition, after an abscess within the teeth, the nerves within the area may become "sensitized" to the effects of stimuli (similar to allodynia). This, complexed with the possible changes within the sodium channels themselves, or perhaps the addition of slightly different sodium channels (NaV1.8/1.9), make it a wonder that we are ever able to get any anesthesia at all with a local infiltration or PDL. Of course, the low pH doesn't help the situation as less local anesthetic is able to reach the nerve itself (see: http://www.frca.co.uk/article.aspx?articleid=220)

I think your best bet if IAN won't work is to go intraosseous.

 

[armorshell]

The problem is that recent research (can't remember study- I'll find it later and cite it) has shown that the success of the IAN decreases as you move anteriorly within the mandible. This is due to the proposed innervation scheme of the IAN. The most distal teeth have fibers running in the outer portion of the nerve, most of which receive adequate local anesthetic from the block. However, deeper within the nerve, the fibers running to the premolars and incisors do not receive an adequate amount of local anesthetic.

I'm not keyed in to the most recent research on the microneuroanatomy of the IA so I'd appreciate a citation. However, that the more distal branches run centrally in the proximal portions is not a recent discovery. Also, unless I'm mistaken, you should be able to verify that you've achieved complete neural anesthesia by verifying soft tissue anesthesia of the ipsilateral lip. Again, this may not be as sensitive for the most distal nerve branches.

Also, I'm ignorant if there are any studies that have been done concerning intraosseous anesthesia and local infective processes, but it seems counterintuitive to try IOA since that itself is a "local infiltration" delivered more directly. It seems to me that may suffer similar inadequacies as a local infiltration delivered through soft tissue, despite having fewer lipid membranes to dissolve through. My heuristic for achieving LA infections has always been "Go as proximal as possible"

 

[jay47]

I'm not keyed in to the most recent research on the microneuroanatomy of the IA so I'd appreciate a citation. However, that the more distal branches run centrally in the proximal portions is not a recent discovery. Also, unless I'm mistaken, you should be able to verify that you've achieved complete neural anesthesia by verifying soft tissue anesthesia of the ipsilateral lip. Again, this may not be as sensitive for the most distal nerve branches.

Also, I'm ignorant if there are any studies that have been done concerning intraosseous anesthesia and local infective processes, but it seems counterintuitive to try IOA since that itself is a "local infiltration" delivered more directly. It seems to me that may suffer similar inadequacies as a local infiltration delivered through soft tissue, despite having fewer lipid membranes to dissolve through. My heuristic for achieving LA infections has always been "Go as proximal as possible"

Finding the citation for the previous post later, but as far as the effectiveness of the IO injection:
Local Anesthesia Strategies for the Patient With a “Hot” Tooth
John M. Nusstein DDS, MSa, , , Al Reader DDS, MSb and Melissa Drum DDS, MS Dental Clinics of North America
"Research on the supplemental IO injection for patients diagnosed with irreversible pulpitis has shown good results. Nusstein and colleagues 8 found that a supplemental mandibular IO injection using 1.8 mL of 2% lidocaine with 1:100,000 epinephrine had a 91% success rate in attaining complete pulpal anesthesia when used after the IANB injection failed. Parente and colleagues 59 reported a success rate of 79% when they used 0.45 to 0.9 mL of 2% lidocaine with 1:100,000 epinephrine. The addition ofa second IO injection increased their reported success to 91%. Reisman and colleagues 60 used 1.8 mL of 3% mepivacaine as a supplemental injection in mandibular, posterior teeth diagnosed with irreversible pulpitis. They reported 80% success with an initial IO injection and 98% success when a second IO injection of mepivacaine was delivered. Bigby and colleagues 61 studied 4% articaine with 1:100,000 epinephrine as an IO supplemental injection in posterior mandibular teeth diagnosed with irreversible pulpitis and reported an 86% success rate when the IANB injection failed. The
Stabident system was used in all these 4 studies"

Perhaps the abscess presents a different situation, but I usually associate an periapical granuloma/abscess with irreversible pulpitis, although the two are not necessarily coupled. Our LA instructor always recommended IO if other techniques are failing.

 

[Streetwolf]

I absolutely see what the OP is saying since I've wondered the same thing. However I recently had a case with a lower canine that I just couldn't get numb when performing RCT. We gave like 2 lido blocks and 2 infiltrations, a carbo infiltration, a septo infiltration, and 2 or 3 lido intrapulpals. Nothing seemed to work.

With 2 blocks you think she would have been a bit better. She definitely had soft tissue anesthesia. It was just that tooth that wouldn't numb up.

We eventually got her numb enough to get working length and a 10-file in the canal. We put her on antibiotics and when she came back a week or two later we were able to successfully finish the root canal without incident.

 

[armorshell]

Perhaps the abscess presents a different situation, but I usually associate an periapical granuloma/abscess with irreversible pulpitis, although the two are not necessarily coupled. Our LA instructor always recommended IO if other techniques are failing.

If a tooth has periapical pathology, IIRC it's generally accepted that it has progressed past irreversible pulpitis into necrosis.

However, that isn't to say that this study has no merit. I actually loved IOA when it was available to me. I'd never really had a use for it as a "rescue" anesthetic but I like the concept. If there's no literature out there on IOA use in cases with periapical pathology/necrosis, that might be a project for a dental student out there.

 

[DrJeff]

I absolutely see what the OP is saying since I've wondered the same thing. However I recently had a case with a lower canine that I just couldn't get numb when performing RCT. We gave like 2 lido blocks and 2 infiltrations, a carbo infiltration, a septo infiltration, and 2 or 3 lido intrapulpals. Nothing seemed to work.

With 2 blocks you think she would have been a bit better. She definitely had soft tissue anesthesia. It was just that tooth that wouldn't numb up.

We eventually got her numb enough to get working length and a 10-file in the canal. We put her on antibiotics and when she came back a week or two later we were able to successfully finish the root canal without incident.

I hate to break it to you, but if you end up doing a bunch of endo and/or restorative dentistry in your career, this most definitely WON'T be the last tooth that you can't get numb. It doesn't happen all that often, but it certainly does happen 🙁

 

[armorshell]

I hate to break it to you, but if you end up doing a bunch of endo and/or restorative dentistry in your career, this most definitely WON'T be the last tooth that you can't get numb. It doesn't happen all that often, but it certainly does happen 🙁

What's your experience with actual "hard to numb" teeth versus patient management issues i.e. nervous patient in pain, jumping every time they feel you put a file in the canal?

I see it all the time (with extractions only of course), and I was wondering if there were similar patients in the endo/restorative realm.

 

[DrJeff]

What's your experience with actual "hard to numb" teeth versus patient management issues i.e. nervous patient in pain, jumping every time they feel you put a file in the canal?

I see it all the time (with extractions only of course), and I was wondering if there were similar patients in the endo/restorative realm.

In my own personal experiences, if you have a "normal patient" (whatever that may be ) who typically doesn't exhibit any outward anxiety in past treatment situations and they're complaining when I put an instrument into the canal space of a "hot" tooth, then I'm going to believe them. If it's an outwardly anxious patient, who has been a bit jumpy from the administration of the anesthesia, the sound of the handpiece, etc, then my brain is thinking more along the lines of a patient management situation vs. a pain management situation 😡 Sometimes you almost know before you begin that it's the patient that's the bigger problem. Fortunately these days I'm much better at spotting those patients far sooner (and comfortable enough to admit that I don't want to treat them less I start loosing more hair off the top of my head or start graying even quicker ) and when I see them coming, I'm filling that referral slip out to my local endodontist very, very quick, and Rx'ing them too as they leave my office. I'll gladly see them back in a few weeks for the crown prep when they're out of pain! 😀

 

[Antz002]

Thank you for all the replies! It seems to me that jay47's point about the nerve fibres possibly becoming hypersensitive makes the most sense in terms of what my supervisor was trying to explain to me

 

[1992Corolla]

I have rarely had a problem with doing a block first, then a mental, then local infiltration/PDL in getting a patient numb.

Like Jef was saying, in the rare case that the patient isn't numb - whether mentally or physically, we give abx and have them come back in 2-3 days.

So far, no problems!

I am curious about technique on some of these injections. I find that on some of these injections I drop the needle down to the inferior border of the mandible to get any potential cervical innervation or 'rogue' nerves as I tell my patient. Buccal and lingual - and really load them up. Of course all I am doing are extractions, but this seems to work every time.