**3. Gow-Gates mandibular nerve block**

Achieving excellence in pain control is an intrinsic, yet challenging, goal of dentistry. Tradi‐ tionally, the inferior alveolar nerve block (IANB), also known as the "standard mandibular nerve block" or the "Halsted block," has been used to provide anesthesia in mandibular teeth. This technique, however, has a success rate of only 80 to 85 percent, with reports of even lower rates. Investigators have described other techniques as alternatives to the traditional approach, of which the Gow-Gates mandibular nerve block and Akinosi-Vazirani closed-mouth man‐ dibular nerve block techniques have proven to be reliable but each of which have merits and

There are many reasons why the success rate of SIANB is low. One is that the dentist can make mistakes during the technique. These problems are easily resolved by reviewing the anatom‐ ical landmarks and the steps to perform the technique involved. Another important reason is the presence of inflamed or infected tissue. Infection areas are acidic, which can influence the beginning of anesthesia. When infection occurs, it is necessary to administer an injection into a deeper location away from infection to avoid this problem. A third reason is that a patient's anxiety often can cause local anesthetic failure. [6] This problem can be solved by the discussion with his fear of injections patient and, if necessary, considering the use of minimal sedation such as that provided by nitrous oxide. Intravascular injection may be another reason for failure because the local anesthetic can be taken away from the site of action. This problem can

Anatomical variability and accessory innervation can also be a problem in providing successful mandibular anesthesia. Once the needle has penetrated the oral mucosa, the dentist is essentially proceeding in a blind mode and assuming that the patient has the same anatomy learned in the dental school. All patients anatomy, however, are not the same and this anatomic

Accessory innervation occurs when the main inferior alveolar nerve trunk is not the only source of innervation to the pulp. This accessory innervation may arise from various sources such as a distinct branch from alveolar nerve [8], mylohyoid nerve, as well as the buccal, lingual or auriculotemporal nerves. This situation can be diagnosed when the patient has signs of a successful mandibular nerve block such as a dormant lip, but the tooth is still sensitive when

Although some researchers report that the success rates for alternative blocks are higher than

ers of the latest study reported that the best rate for SIANB was probably due to the experience

The main objective of each block of the mandibular nerve is the inferior alveolar nerve anesthesia, which innervates the pulps of the lower teeth, as well as the buccal periodontium anterior to the mental foramen. This is achieved by depositing the anesthetic within pterygo‐

others reported comparable rates [11,12]. However, research‐

**2. Standard Inferior Alveolar Nerve Block (SIANB)**

44 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

be avoided by careful aspiration before any injection [7].

variability can lead to failure of SIANB. [8]

stimulated with a drill [8,9].

those reported for SIANB [8,10],

of dentists who administer the anesthetic blocks. [12]

draw backs [5].

Gow-Gates initially described what became known as the "Gow-Gates mandibular nerve block" in 1973. The aim of the technique is to place the needle tip and administer the local anesthetic at the neck of the condyle. This is in proximity to the mandibular branch of the trigeminal nerve after it exits the ovale foramen. Before looking inside the patient's mouth it is necessary to establish the extra-oral reference points. An imaginary line is drawn from the intertragus notch (the point immediately inferior to the tragus of the ear) to the corner of the mouth. Then we align the syringe parallel to this plane during insertion.. Inside the mouth, we have to find the bony landmark by palpating the external oblique ridge of the anterior surface of the ramus in the coronoid notch. The temporal muscle attaches onto the coronoid process, and it is important to feel this muscle when inserting the needle. After palpating the landmarks, we must keep the syringe at the correct angle, as determined previously, with the needle tip aiming for the neck of the condyle. The barrel of the syringe usually is over the contralateral mandibular canine or premolars [12,13].

The intraoral insertion point is lateral and superior when compared with that of the SIANB. This point is on the lateral margin of the pterygotemporal depression and just medial to the attachment of the temporal muscle. The upper boundary of the insertion point is the maxillary occlusal plane. Usually, the needle lies just below the mesiopalatal cusp of the maxillary second molar, which can be a reliable landmark [13].

Just before the needle insertion, we ask the patient to open his mouth as widely as possible. The wide opening is critical to the success of this technique. Once the needle is inserted, is moved forward slowly until it contacts bone (the condyle neck). This contact should occur at a depth of 25 millimeters. If bone is not contacted, we should not apply the injection, but instead redirect the needle until we feel the neck of the condyle. Once contact is made, we remove the needle 1mm and administer a full cartridge of local anesthetic after a negative aspiration. We should not administer less than a full cartridge [12,13].

The final position of the needle tip is just anterior to the neck of the condyle, inferior to the lateral pterygoid muscle, lateral to the medial pterygoid muscle and medial to the ramus. The nerves anesthetized by Gow-Gates technique include the inferior alveolar and its branches (incisors and mental), lingual, mylohyoid, auriculotemporal and buccal (about 75 percent of the time). Anesthesia of the mylohyoid and auriculotemporal nerves resolve the concern with accessory innervation, as would be the uppermost position of the anesthetic administration. The gow-gates technique resulted in a rate of about 2% positive suction compared with 10 to 15% SIANB. [1] This rate may be lower because the inferior alveolar vein and artery are further away than the target site are to SIANB [9, 10,12,13].

After the injection is administered, we should ask patients to keep their mouths open for at least 20 seconds, if possible, to keep the inferior alveolar nerve closer to the site of injection and improve onset of anesthesia. The onset of anesthesia is usually five to 10 minutes, which is longer than that for the SIANB (usually three to five minutes) [13].
