Failure of mandibular nerve blocks

[Smilemaker100]

Hello everyone!

The failure to achieve adequate inferior alveolar nerve anesthesia is pretty relevant not only to those in dental school but also for those individuals who are in general practice as studies have shown that even experienced dentists have a failure rate as high as 20% in achieving a successful mandibular block on first attempt .

I have been thinking over this issue ( I think too much sometimes 🙄 -maybe I need more distractions 😉 )as I have been doing quite a number of extractions these days. I was especially concerned when I came across this particular patient a few days ago. I had extracted teeth # 18, 19 & 20 with no problem, however, when I reflected a flap and attempted to extract an impacted , mesio-angular and buccally inclined # 17, the patient was quite sensitive. The "lip sign" was present and the buccal mucosa seemed to be adequately anesthesized . When the attending came to give a hand (he has a lot of surgical experience and is a very good clinician 👍 ), he attempted to remove tooth # 17 as atraumatically as possible. None of the additional injections he administered seemed to alleviate the patient's sensitivity 🙁 .

The most common cause of mandibular block failure is due to an erroneously placed injection. However, there are anatomical considerations to consider as well. There exists accessory innervation of the mandibular teeth which most suspect is due to:

1)the mylohyoid nerve -usually concerns the first mandibular molar.
The mylohyoid injection should be against the mandible in the lingual area of the apex of the lower 2nd molar.

2)a bifid mandibular canal - studies have shown that this occurs at a rate of 0.95% . It has so many variations- of particular relevance is that variation in which there are two separate foramina. In such cases, sometimes you may have to deposit some more anesthetic inferior to the normal anatomical landmark.

3) upper cervical nerve plexus - when someone mentioned this possibility to me , it rang a bell because I remember reading some articles on trigemino-cervico convergence for my master's thesis a few years ago. Research has shown that the spinal nucleus of nerve V/subnucleus caudalis/caudalmost part of the descending tract of the fifth nerve in the brainstem overlaps with the dorsal roots of the second, third and fourth cervical segments (C2 being of particular importance). Upper cervical rhizotomies will result in denervation of the lower jaw .

I don't know much on how to give a deep cervical block but I read that it is given over the external oblique ridge, like if one is giving a long buccal, but the needle is advanced toward the angle of the mandible.

Anyone have opinions on this? Any other suggestions? 😕

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[toothcaries]

personally...i always give a pdl for extractions also.
it usually does the trick


and for the ornery nerves that just dont wanna cooperate..use the gow-gates and block a little higher...

 

[Smilemaker100]

personally...i always give a pdl for extractions also.
it usually does the trick


and for the ornery nerves that just dont wanna cooperate..use the gow-gates and block a little higher...

PDL injections did not help for that particular patient.

 

[saahakhan]

hi everyone,
is it possible for a patient to go into convulsion due to improper inferior alveolar block. i have come to heard tht if u inject LA near facial nerve it cause this sort of problem.

 

[aphistis]

hi everyone,
is it possible for a patient to go into convulsion due to improper inferior alveolar block. i have come to heard tht if u inject LA near facial nerve it cause this sort of problem.

Bell's palsy is a much more likely result than convulsions. If you anesthetize a motor nerve, how could it stimulate convulsions in its muscles if it can't conduct AP's?

(disclaimer: I have no anesthesia training yet, so take this alongside what you paid for it.)

 

[DcS]

An excellent alternative to an IANB is the Gow-Gates nerve block. Most practitioners don't learn it because it tends to have a high learning curve, but once mastered success rates range up around 98%. Your target it basically to hit the condyle with your injection, I like it because you really have something palpable to aim for. You have your pt lie parallel to the floor, and opening as wide as they can you can put your index finger of your non-injecting hand on the condyle so you have some type of landmark. The site of injection is distal to the 2nd max molar, usually at the level of the mesiolingual cusp. You come from the corner of the opposite side of the mouth, and you aim along a line that extends from the corner of the mouth to the intratragic notch. People get a little squimish about doing it...I can tell you from experience it's not bad. I had to do it one time on a pt with unusual anatomy for which an IANB would not work. Ever since I have used it frequently with 100% success...have not had one fail yet. You should check it out, it will anesthesize the full quadrant, and soft tissue buccal and lingual as well.

 

[Dr.SpongeBobDDS]

Did my first Gow-gates a couple weeks back on a classmate. I was a little nervous at first cause it seemed like I was waaay back there. 😱 It really wasn't that bad though and he got profoundly numb on half a carpule.

Our instructor cited a figure of >95% success rate with gow-gates whereas IANB has a relatively significant failure rate (was it 15-20%? can't remember exactly) even with meticulous technique. Maybe the anatomy is just more consistent from person to person as you move higher up the nerve? Anybody know the answer to this one?

 

[toothcaries]

i'm also a big fan of the gow-gates..
...however, i've only used it as a secondary techique in oral surgery.

here's a simple technique learned from an resident...
-have pt open wide
-your landmark= tragus
-from mesial lingual of the opposite 1st molar, aim for the tragus.
-advance until u hit bone (anterior surface of condylar neck)
-dispense anesthetic
(i hope i explained this correctly)

i can count on one hand the number of times i've had to do the "high block"...but so far it's been effective.

An excellent alternative to an IANB is the Gow-Gates nerve block. Most practitioners don't learn it because it tends to have a high learning curve, but once mastered success rates range up around 98%. Your target it basically to hit the condyle with your injection, I like it because you really have something palpable to aim for. You have your pt lie parallel to the floor, and opening as wide as they can you can put your index finger of your non-injecting hand on the condyle so you have some type of landmark. The site of injection is distal to the 2nd max molar, usually at the level of the mesiolingual cusp. You come from the corner of the opposite side of the mouth, and you aim along a line that extends from the corner of the mouth to the intratragic notch. People get a little squimish about doing it...I can tell you from experience it's not bad. I had to do it one time on a pt with unusual anatomy for which an IANB would not work. Ever since I have used it frequently with 100% success...have not had one fail yet. You should check it out, it will anesthesize the full quadrant, and soft tissue buccal and lingual as well.

 

[Smilemaker100]

I am well aware of the Gow-Gates method as well as the Vazirani-Akinosi method ( which is used when a Gow-Gates cannot be performed such as when there is limited mandibular opening- trismus). These methods are described in "Handbook of Local Anesthesia" 4th ed. by Stanley F. Malamed
on pages 203-212.

I am presently doing my first year of a residency program. It doesn't seem like a lot of the attendings do Gow-Gates (as far as I know) except for the endodontist and another resident. I was taught about the alternative while in dental school. My residency director told me that it is better to learn how to master the inferior alveolar nerve block before doing Gow-Gates. This is what Dr Malamed states on page 203 of the previously mentioned book:

"The incidence of unsuccessful anesthesia with the Gow-Gates method may be as high ( if not higher than) that for the inferior alveolar nerve block until the administrator gains clinical experience with it." Therefore, the rate of success with Gow Gates is high with those that have experienced hands.

How many people out there were taught to do the Gow-Gates method while in school? While I was in school, the attendings would do Gow-Gates but didn't let the students do it. They told me that I would probably learn how to do it on patients as a resident.

 

[toothcaries]

well..
i remember GG was mentioned in a 3rd year oral surgery class at osu...

...but i learned the technique clinically(again as a 3rd)...informally from one of the oral surgery residents.


i also learned from another resident the stadodent intraosseous technique (drill hole distal to tooth into attached gingive..great for RCT)...
...but i have no practice with it yet.

I am well aware of the Gow-Gates method as well as the Vazirani-Akinosi method ( which is used when a Gow-Gates cannot be performed such as when there is limited mandibular opening- trismus). These methods are described in "Handbook of Local Anesthesia" 4th ed. by Stanley F. Malamed
on pages 203-212.

I am presently doing my first year of a residency program. It doesn't seem that a lot of the attendings do Gow-Gates except for the endodontist and another resident. I was taught about the alternative while in dental school. My residency director told me that it is better to learn how to master the inferior alveolar block before doing Gow-Gates. This is what Dr Malamed states on page 203 of the previously mentioned book:

"The incidence of unsuccessful anesthesia with the Gow-Gates method may be as high ( if not higher than) that for the inferior alveolar nerve block until the administrator gains clinical experience with it." [Therefore, the rate of success with Gow Gates is high with those that have experienced hands[/I].

How many people out there were taught to do the Gow Gates while in school? While I was in school, the attendings would do Gow Gates but didn't let the students do it. They told me I would probably learn how to do it on patients as a resident.

 

[Dr.SpongeBobDDS]

I'm only a second-year and it is one of the first techniques we were taught. In clinic, the "old-timers" insist on IANB because gow-gates scares them a little. But we were taught in our anesthesia course to use gow-gates for the average patient whenever the faculty will allow it; you anesthetize a greater area reducing the number of injections you need to give, you minimize the dose of anesthetic delivered and practically eliminate the need for a repeat injection due to missed blocks.

 

[grtuck]

It was one of the injections we were supposed to pass off in our anesthesia class to be considered "ready" to provide injections for patients. We all had to practice it along with the other ones that can be done for that area. Our instructor did tell us that many of the old time faculty might be a little nervous about us using it, but he wanted us to be able to use it whenever the need arised because it is so successful once you get past the learning curve.

grtuck

 

[DcS]

i'm also a big fan of the gow-gates..
...however, i've only used it as a secondary techique in oral surgery.

here's a simple technique learned from an resident...
-have pt open wide
-your landmark= tragus
-from mesial lingual of the opposite 1st molar, aim for the tragus.
-advance until u hit bone (anterior surface of condylar neck)
-dispense anesthetic
(i hope i explained this correctly)

i can count on one hand the number of times i've had to do the "high block"...but so far it's been effective.

I would add 1 very important step to this sequence. In between advancing and deposition, as with every block make sure to aspirate. Speaking of aspiration, another advantage b/w the gow-gates and IANB is that with the GG the aspiration rate is only 2%, while with IANB it is in the area of 10-15%.
Someone asked the success rate, and my memory was a bit off...according to Malamed in "Handbook of Local Anesthesia", success rates over 95% are common. The number in my memory was the success rate of George Gow-Gates, 99%.