LA Sheet #14 (last lec) By Lama Alsayed

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LA Sheet #14 (last lec) By Lama Alsayed

Post by Sura on 31/12/2011, 10:55 pm

http://www.mediafire.com/?80dgawm0numm5xt
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Sura

عدد المساهمات : 484
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تاريخ التسجيل : 2010-09-29

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Re: LA Sheet #14 (last lec) By Lama Alsayed

Post by Shadi Jarrar on 15/1/2012, 3:09 pm

Techniques of mandibular anesthesia

Abriviations:

IANB= inferior alveolar nerve block

Gow- gates and Akinosi techniques are alternative techniques that are used to overcome the failure or incomplete anesthesia that might result after using the conventional methods.
the most common conventional method in our practice is the Inferior alveolar nerve block (IANB) which has a success rate of about 80% meaning that 1 of every 5 patients won’t have adequate anesthesia that’s why we have to look for other alternatives, especially in the mandible because it has a very thick bone and a lot of accessory innervations and anatomical variations.



The Gow – Gates technique:

The idea of this technique is to deposit the local anesthetic solution just close to the nerve trunk, so for that reason it’s regarded as a true mandibular nerve block; therefore we expect that all branches of the mandibular nerve to be anesthetized. And by that we will overcome all accessory innervations and anatomical variations.



Target area:

The target area is lateral to the condylar neck, just below the insertion of the lateral pterygoid muscle


so we will deposit the local anesthetic just close to the neck of mandibular condyle when the patient widely open his mouth , which means that the neck of the mandibular condyle would be very close to the nerve trunk by about (0.5 -1 cm ) .

if the patient slightly close his mouth the neck of the condyle will be so far from the nerve trunk when the patient open his mouth widely this will translate the condyle more anteriorly in order to make the target point closer to the medially positioned nerve trunk .and this will result in a space of 0.5 – 1 cm from the insertion point to the nerve trunk, unlike the IANB in which the insertion point is very close to the nerve. So for that reason we expect a slower onset of action


Slower onset of action associated with this technique has two reasons:

1. The distance of the nerve trunk from the deposition site.

2. The size of the nerve trunk being anesthetized (approximately 5-10 mm).



The main disadvantages of Gow- gate technique are:

1. Longer onset of action.

2. And the difficulty of this technique.




Nerves anesthetized:


single one injection can provide anesthesia for all branches of the third division of the trigeminal nerve (the mandibular trunk), that include:



1. Auriculotemporal nerve.

2. Mylohyoid

3. Inferior alveolar.

4. lingual.

5. Mental

6. Incisive

7. Long Buccle.



The long buccle nerve is situated in the most anterior area of the trunk so LA solution might not reach it and we might end of incomplete anesthesia for the long buccle nerve, we can achieve long buccle nerve anesthesia in about 75% of the cases. Where other branches can be 100% anesthetized.




Land marks:

1. Line connecting the Intertragic notch and the corner of the mouth, the syringe and the needle have to be parallel to this line






2. The insertion point is located in the mucus membrane of the anterior border of the ramus; just distal to the upper second molar, the needle will be at the level of the mesio-palatel cusp of the second upper molar tooth.




Note: in this technique we don’t need to palpate and determine the coronoid notch because the insertion point is higher than the coronoid notch.

v The target area is approached from the contra -lateral side, and the syringe barrel lies in the corner of the mouth over the premolars but its position may vary from molars to incisors, depending on the divergence of the ramus. ( see figure 14-21, page 241)

We can determine the degree of the ramus divergence by looking at the angle between the ear and the face some people have their ears severely divergent others are moderate or mild, so the divergence of the ear will be consistent with the divergence of the ramus.



Depth of penetration:

As a rule the depth of penetration for IANB, Gow-Gates and Akinosi is the same which is 25 mm for normally sized patients, which means that two thirds of the long needle will be inside the tissue. Special accommodation can be done for small or large sized patients according to the anterio-posterior dimension of the ramus.

SO in this technique you have to advance the needle to the adequate depth (25 mm) until you feel Bony contact.



Bony contact in this technique is a safety feature, this contact will be on the lateral aspect of the condylar neck, if there is no bony contact don’t deposit any amount of local anesthetic solution

Failure to contact bone is attributed to two main factors:

1. The medial deflection of the needle , in this case u have to move the syringe more Posteriorly so the needle will go more anteriorly .this is done after assuring that the patient wildly open his mouth in order to get the condylar neck as close as possible to the trunk.

2. Partial closure of the patient’s mouth; which can cause increase in the thickness of soft tissue and movement of the condyle more distally.

Aspiration:

After achieving bony contact you have to aspirate , one of the most important advantages of this technique is that positive aspiration rate is around 2% compared to (10%- 15%) of the inferior alveolar nerve block

if there is positive aspiration this means that you have touched the internal maxillary artery



Deposition of local anesthetic solution inside the internal maxillary artery will result in reverse flow of the solution to the external Carotid artery, which will transmit the solution to the cavernous sinus inside the brain which contain the 3rd, 4th and sixth cranial nerves that are responsible in the motor movement of the eye, so this patient will have Transient diplopia for about 20 min, in this case just cover the patient’s eye in order to prevent the corneal damage.

v If Aspiration is negative deposit about 1.8 ml which equals a whole carpule.







Akinosi technique:

It is also called closed mouth technique, because it is performed when the patient is unable to open his/her mouth widely



Indications:
1. Limited mandibular opining (e.g. Trismus is an indication if it was unilateral not bilateral)


2. Inability to visualize land marks for IANB (e.g. large tongue that interfere in locating of the point of insertion for the IANB or Gow-gates)



Note: in the Akinosi technique the target area would be in the midway between the IANB and Gow –Gates nerve block.

An important point in this technique is that you won’t feel bony contact. Just insert the needle to the adequate depth about 25 mm in normally sized patients, aspirate and deposit the solution

Target area:

It is located in the pterigo-mandibular space below the neck of mandibular condyle and above the lingula,


Nerves anesthetized:

All motor and sensory branches of the mandibular nerve will be anesthetized, the motor branches are the first target because when they are anesthetized muscles of mastication will be relaxed and the patient will be able to open his mouth, the motor branches will be anesthetized faster than the sensory branches because the sensory have larger size.



v The target area is very important to be located as lateral as possible, because if we were slightly medial then local anesthetic solution will be deposited medial to the sphenomandibular ligament, and this ligament will prevent the diffusion of the local anesthetics to the mandibular nerve this will result in failure of the anesthesia, and this is the main reason of failure of anesthesia in Akinosi method.

v Note: incase of limited mouth opening due to hot infection (acute molar infection for example) conventional methods of anesthesia might be ineffective so you can perform this method .

The insertion point:

Mucus membrane in the anterior surface of the ramus

The syringe barrel and needle, should be parallel to the mucogingiveal junction

You have to be straight during insertion of the needle until you reach adequate depth of penetration about 25 patients in normally sized patients.

To avoid deflection of the needle medially, the Bevel of the needle should be directed toward the Medline.

So when u reach the adequate depth of penetration there would be no boney contact aspirate, if negative deposit the recommended amount which is a whole dental carpule.



The doctor asked the following question:

Ahmad visited you asking for extraction of the lower wisdom tooth but he is unable to open his mouth so administered the Akinosi block, However motor paralysis is present but sensory analgesia is inadequate to permit the dental procedure to begin, what block can be administered to permit the dental procedure to begin?

The answer is: the inferior alveolar nerve block.

Don’t give the Akinosi block again there is no indication now after achieving the motor paralysis

In Akinosi method you will achieve anesthesia for all branches of the mandibular nerve; motor and sensory branches, but you would need a supplementary injection for posterior molar teeth in order to do your extraction or your surgical procedure

So the difference between Gow –gates and Akinosi method is that Gow- Gates would provide adequate anesthesia in one injection where in the Akinosi you might need a supplemental injection.





In summary: in the gow-gates technique the target point is close to the nerve trunk, close to the lateral aspect of the condylar neck. For the inferior alveolar nerve block it is the lingula and between them is the Akinosi





Another question by the Doctor:

Which of the following injection is not recommended?

1. Topical

2. Submucosal infiltration

3. Subperiosteal infiltration.

4. Nerve block analgesics

5. Intraligamental anesthesia

6. Intraosseous analgesics.

The answer is : subperiosteal infiltration , because after several researches made they found that subperiosteal and submucosal infiltrations have the same effectiveness of anesthesia , so we can replace the subperiostealinjection because it’s painful , since the periosteum is highly innervated and touching it would be very painful.


Good luck
Done by: Lama Alsayed
Last lec. For D. Alshayab
date of the lec: 28/12/2011
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Shadi Jarrar
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عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

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