The following 3 techniques are used to perform a mandibular nerve block:
1. Gow-Gates technique
2. Vazirani-Akinosi technique
3. Coronoid approach
For a clear understanding of the technical descriptions that follow (see below), it is important to be conversant with some dental anatomic terminology. These terms may be illustrated by considering the anatomy of the second maxillary molar tooth.
The second maxillary molar tooth is placed between the first and third molar teeth and is the seventh tooth from the midline. The visible part of the tooth is called the crown, and the parts covered by the gum are the 3 roots of the tooth. The dividing line that separates the roots from the crown is called the cervical line.
The crown has the following 5 surfaces:
- Occlusal
- Buccal
- Lingual (palatal)
- Mesial
- Distal
The occlusal, buccal, and lingual surfaces are self-explanatory, referring to those particular surfaces of the tooth. The mesial surface is the anterior surface of the tooth—in this case, the surface adjoining the first molar tooth.
The distal surface is the posterior surface—in this case, the surface adjoining the third molar tooth.
The buccal surface of the tooth has the following 2 protuberances or cusps, which are separated by the buccal groove:
An anterior protuberance, called the mesiobuccal cusp
A posterior protuberance, called the distobuccal cusp
Similarly, the lingual surface has a mesiolingual cusp and a distolingual cusp, which are separated by the lingual groove.
► See also: DENTAL ANESTHESIA : Mandibular Anesthesia : Gow-Gates technique
Techniques for Mandibular
1. Nerve Block Gow-Gates technique
This technique is mainly indicated in patients undergoing dental procedures in whom inferior alveolar nerve block does not provide adequate analgesia owing either to anatomical variation or due to accessory nerve supply.
This approach provides true mandibular nerve block as it blocks the trunk of the nerve before it divides into its three main terminal branches. The incidence of intravascular injection is also lesser with this approach.
A disadvantage of this approach is that there is undesired anesthesia of the lower lip and temporal region. The onset time of the block is also prolonged. The patient is placed in a semisupine position or on a dental chair with the operator standing on the same side as the block to be performed. The mouth is opened as wide as possible.
This is essential for the success of this block. Anatomic landmarks include the following:
Corner of the mouth
The intertragic notch
Distolingual cusp of the second maxillary molar tooth
The aim is to reach the neck of the mandibular condyle.
The second maxillary molar tooth is identified, and a needle is inserted at the level of the mesiolingual cusp along the medial side of the mandibular ramus (see the image below). The point of insertion is much higher than that for an inferior alveolar nerve (IAN) block. The needle is inserted in such a way that it lies parallel to an imaginary line drawn from the intertragic notch to the angle of the mouth.
The needle is advanced by 2.5 cm so as to contact the bony neck of the mandibular condyle. It is then slightly withdrawn, and negative aspiration is confirmed in 2 planes. Finally, 1.8 mL of local anesthetic is injected slowly over 1 minute. This blocks the IAN and its branches and the lingual, mylohyoid, auriculotemporal, and buccal nerves.
2. Vazirani-Akinosi (closed-mouth) technique
The Vazirani-Akinosi technique has several advantages over the Gow-Gates technique. It is useful in trismatic patients and those with ankylotic temporomandibular joint; in addition, it is less traumatic and has a lower complication rate.
However, the Vazirani-Akinosi technique is less effective than the Gow-Gates technique. Recent studies have not shown any difference in the quality of pain relief with either of the approaches. This approach is contraindicated if the patient has an infection or inflammation involving the pterygomandibular region or maxillary tuberosity. The main advantages with this approach include a faster onset of action, lesser post-procedure complications, and lesser pain during injection.
The patient is placed in a semisupine position or on a dental chair with the mouth closed. The operator stands on the same side as the block to be performed. Anatomic landmarks include the following: Gingival margin over the second and third maxillary molars
Pterygomandibular raphe
The aim is to enter the pterygomandibular space where the IAN, lingual nerve, and mylohyoid nerve are present. This space is bordered laterally by the ramus of mandible, medially and inferiorly by the medial pterygoid muscle, posteriorly by the parotid gland, and anteriorly by buccinators muscle.
The cheek is retracted with a retractor, and the patient is asked to occlude his or her teeth gently. The needle is inserted over the medial aspect of the mandibular ramus, parallel to the occlusal plane at the height of the mucogingival junction of the second and third molars (see the image below). The needle is bent slightly to decrease the chance of entering the muscle belly.
The needle is then advanced through the mucous membrane and buccinator muscle to enter the pterygomandibular space. The needle is advanced until the hub is level with the distal surface of the second molar. After negative aspiration, 1.8 mL of local anesthetic is injected slowly over 1 minute.
3. Coronoid approach
The patient is placed in a supine position with the mouth in a neutral position. The coronoid notch on the side of the block is identified by opening and closing the mouth a few times.
After skin preparation, a 22-gauge needle is inserted at the middle of the notch and advanced to a depth of about 1-2 inches in a plane perpendicular to the base of the skull until the lateral pterygoid plate is reached.
The tip of the needle is then withdrawn slightly and redirected posteriorly and inferiorly so that it goes beyond the lateral pterygoid plate. After redirection of the needle, paresthesias in the mandibular region are elicited at a depth of about 1 cm. After aspiration, 3-5 mL of local anesthetic solution is slowly injected.
Fuente: emedicine.medscape.com
Author: Anusha Cherian
Coauthor(s):Nanda Kishore Maroju