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Simplifying the Gow-Gates Mandibular Division Block Injection
Posted: 1/29/2018


A simplified Gow-Gates injection technique has been taught at the University of the Pacific, Arthur A. Dugoni School of Dentistry for several years, and has been found to be easily mastered by dental students and by practicing dentists and dental hygienists attending hands-on training courses. This modification builds upon both the original description of the technique by Dr. Gow-Gates and the later modified descriptions of other authors, but incorporates a simpler method for determining the correct target point and the proper angulation of the syringe in the medial-lateral orientation.

 

Steps:

1.      Observe and extraorally palpate the head of the condyle as the patient opens and closes their jaw.  With jaw movement, the head of the condyle can be seen as it typically bulges out, and it can be felt as it slides anterior-posteriorly over the articular eminence of the temporal bone.  After first palpating the bulging condylar head extraorally, slide your finger inferiorly below the head of the condyle, and then posteriorly behind the neck of the condyle.

2.      With the patient’s mouth wide open and your finger behind the condylar neck, palpate the anterior border of the ramus intraorally, either at or slightly above the depth of the coronoid notch.

3.      Insert the needle at the intraoral penetration site and aim the needle directly towards your finger. We teach a penetration site similar to that of Malamed’s at a level just below the mesiolingual cusp of the maxillary second molar and just distal to this tooth. Because the finger is held posterolateral to the targeted neck of the condyle, it is directly behind the bony injection target.  As long as the needle is aimed directly towards the finger/condylar neck from the penetration site, failure to contact bone is unlikely. Alignment of the injection path with the extra- and intraoral landmarks is easily assessed both when applying topical anesthetic before the injection and during the injection by simply “leaning back” from the oral cavity and visually checking that the needle pathway intraorally is directed towards the fingertip behind the condylar neck extraorally, and correcting the needle direction as necessary (Figure 1).

 

Note:

The patient’s mouth must be fully open throughout all phases of the Gow-Gates injection.  The condyle then assumes an anterior position over the articular eminence of the temporal bone that is immediately lateral to the trigeminal mandibular division nerve trunk as it emerges through the foramen ovale into the infratemporal fossa.

 

Advantages:

1.      High Success rate: As with all variations of the Gow-Gates technique, the greatest advantage is the high success rate for anesthesia of all the sensory branches of the mandibular division of the trigeminal nerve with a single injection.

2.      Safety: The high success rate is coupled with a very low incidence of complications such as positive aspirations, hematoma, trismus, or nerve injury.

a.      Positive aspiration at the injection site is very low with the Gow-Gates technique with a reported incidence of less than 2%. This is due to the needle passing through a region of relatively avascular loose fatty areolar tissue on its course to the anterolateral neck of the condyle.

b.      The incidence of trismus is also extremely low due to the passage of the needle below the insertion of the inferior head of the lateral pterygoid muscle onto the superior aspect of the condylar neck and medial to the position of the medial pterygoid muscle.

c.       Nerve injuries, such as paresthesia, are rarely observed with the Gow-Gates technique. At the bony contact site, the needle is 10 to 20 mm lateral to V3 so direct contact with this large neurovascular bundle is avoided, and the deposition site is far enough away from the bundle that potential chemical injury to the nerves by high concentration local anesthetics is also minimized.

 

Familiar landmarks: With palpation of the anterior border of the mandibular ramus intraorally and the posterior border of the ramus extraorally, the landmarks used are similar enough to the familiar traditional inferior alveolar nerve block landmarks that practitioners are immediately confident with them. Use of these familiar and definitive mandibular landmarks anteriorly and posteriorly also enables use of the mind visualization skills that are used with the traditional IA block technique. However, instead of visualizing a “bisection” point for bony contact between the two landmarks, we are visualizing a path aimed directly at the posterior landmark. It is in large part because of this similarity of visualization skills that both inexperienced dental students and seasoned practitioners are able to more quickly master consistent success with this simplified Gow-Gates injection technique. It is also our experience that palpation of the neck of the condyle relative to the anterior border of the ramus provides a more individual, and therefore more accurate, assessment of the posterior degree of flare to the posterior ramus rather than relying on the soft tissue variability of the angulation of the tragus away from the face (Figure 2).

 

Figure 1. Alignment of the injection path with the extra- and intraoral landmarks is easily assessed at the beginning of the injection by simply “leaning back” from the oral cavity and visually checking that the needle pathway intraorally is directed towards the fingertip behind the condylar neck extraorally.  Direction of the needle can be monitored and corrected as necessary throughout the injection process.   

 

Figure 2. Palpation of the neck of the condyle relative to the anterior border of the ramus provides a more individual, and therefore more accurate, assessment of the posterior degree of flare to the posterior ramus rather than relying on the soft tissue variability of the angulation of the tragus away from the face (Jastak, Yagiela & Donaldson, Local Anesthesia of the Oral Cavity, W.B. Saunders Company, 1995)

 

Alan W. Budenz, MS, DDS, MBA is Professor in the Department of Biomedical Sciences and is Interim Chair of the Department of Diagnostic Sciences at the University of the Pacific, Arthur A. Dugoni School of Dentistry in San Francisco, California. He received his graduate degree in Anatomy from the University of California, Los Angeles, and his dental degree from the University of California, San Francisco. He has more than 35 years of general practice experience in San Francisco, serves as a general dentistry clinical floor instructor, and has taught general dentistry, local anesthesia, radiology, and anatomy courses at Pacific since 1984.

 

At this year’s 106th Thomas P. Hinman Dental Meeting, Dr. Budenz will be presenting lectures on local anesthesia and the anatomical basis of dentistry and two hands-on workshops on local anesthesia techniques. View his courses lineup here. 





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