**3. Mandibular anesthesia**

There is a great variety of techniques for anesthetizing different regions of the mandible, the most common and useful ones are described in this section.

#### **3.1. Inferior alveolar nerve block**

**Figure 1.** The superficial branches of the trigeminal nerve

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**Figure 2.** Branches of the trigeminal nerve

The inferior alveolar nerve block (IANB) is one of the most important and commonly used techniques in dentistry. Unfortunately it is also the most frustrating with the highest percent‐ age of failure even when properly administrated [1].The IANB anesthetizes the IAN (a branch of mandibular division of the trigeminal), incisive nerve, mental nerve and commonly (but not always) the lingual nerve of the injected side. This block effects the sensation of all the teeth on one side of mandible, the bone from the inferior portion of ramus to the midline, the lingual soft tissue and periosteum of the mandible, buccal soft tissues anterior to the mental foramen and anterior two thirds of the tongue and floor of the oral cavity [2].

In one technique, the patient is positioned supine (recommended) or semi-supine. The thumb of the free hand is placed on the coronoid notch retracting the soft tissues. The insertion point of the needle is about 6 to 10 mm above the occlusal plane and at the 3/4 of the anterior posterior distance from the coronoid notch to the pterygomandibular raphe (visual in the oral cavity). The syringe is advanced from across the lower premolar teeth of the opposite side. A long dental needle is used; the bone must be touched while advancing about 25mm of the 35 mm needle into the tissue. After contacting bone the needle is withdrawn slightly, aspiration performed and if negative in two directions 1.5 to 1.8 ml of solution is deposited over a minimum of 60 seconds (Figure 3).. [1]

Two problems occur very commonly with this technique [7]:

**1.** Contacting the bone too soon: to solve this problem the needle is withdrawn halfway, still remaining in the soft tissue, then the barrel of the syringe is swung over the mandibular

**Figure 3.** The Inferior Alveolar Nerve Block

teeth of the side being anesthetized, then the needle is advanced about 2.5 mm and the solution is deposited. This is a modification of IANB (the indirect technique) [8].

**2.** The bone is not contacted after 30 mm of needle insertion: the needle should be withdrawn halfway back then the barrel of the syringe is swung over the molar teeth of the opposite side being anesthetized, and then advanced to touch the bone and then continued as described. When the bone is not touched the solution should not be deposited because the needle could be in the parotid gland near the facial nerve and an injection there could lead to transient paralysis of the facial nerve [1].

One of the most common causes of failure of IANB is depositing the solution too low (below the mandibular foramen) in this case it can be corrected by re-injecting at a higher site, approximately 5 to 10 mm above the previous site.

Mylohyoid nerve is the most common nerve which provides mandible teeth with accessory sensory innervation (most commonly the mesial portion of mandibular first molar). A supplemental injection at the apical region of the tooth in question on the lingual side will solve the problem [9].

Incomplete anesthesia of the central and lateral incisors is due to overlapping fibers of the contralateral inferior alveolar nerve. In this case a supplemental injection with infiltration technique or PDL injection should be done [1].

Olsen reported that in children the mandibular foramen is situated at a level lower than the occlusal plane [10]. Therefore in pediatric patients the injection must be made slightly lower and more posteriorly than for an adult patient.

### **3.2. Vazirani-Akinosi (closed mouth) mandibular block**

Dr. Joseph Akinosi described a close-mouth approach in 1977 [11]. This technique became a successful alternative for inferior alveolar and Gow-Gates mandibular nerve blocks. In 1960 a very similar technique was described by Vazirani, there for the term "Vazirani-Akinosi" is used for the approach. It is also known as "Close-mouth mandibular nerve block" and "Tuberosity approach". Although this technique can be used whenever mandibular anesthesia is desired, its primary indication is in situations where the patient has a limited mouth opening range such as patients with trismus or when spasm of the masticatory muscles on one side of the mandible occur due to several unsuccessful attempt to anesthetize it with IANB, the Vazirani-Akinosi anesthesia approach provides successful anesthesia and a motor blockade (of V3 division of trigeminal nerve) to relieve trismus if it is produced secondary to muscle spasm.

In 1992, Wolfe described a modification of the Vazirani-Akinosi technique, in which the needle is bent at a 45 degree angle to adapt better with the lingual aspect of the ramus. But due to the increase risk of needle breakage this technique cannot be recommended [12]. If the Vazirani-Akinosi technique administered successfully anesthesia of inferior alveolar, incisive, mental, buccal, lingual and mylohyoid nerves is obtained.

For administration of this technique a 25 or 27 gage needle is used. The patient should be positioned supine or semisupine. The index finger or thumb is placed on the coronoid notch reflecting the tissue on the medial side of the ramus laterally. The patient is asked to occlude gently with cheeks and muscles of masticatory relaxed. The syringe is held parallel to the maxillary occlusal plane, with the needle at the mucogingival junction of maxillary third molar (or second molar). The bevel of the needle should be held toward the bone. The needle is inserted to the soft tissue overlying the medial border of the mandible ramus at the point described, and is advanced 25mm (for an average-sized adult) posteriorly and slightly laterally. After negative aspiration in two planes the anesthesia solution can be deposited. Motor nerve paralysis is the first sign to occur so a patient with trismus will notice increased ability to open the jaw. After 1 to 1.5 minute anesthesia of the lip and tongue is noted, and the dental procedure usually can start within 5 minutes.

It is shown in studies that the Vazirani-Akinosi technique has the same success rate of conventional IANB. But with fewer complications and a lower aspiration rate (<10%) [1].

#### **3.3. Gow-Gates mandibular nerve block**

teeth of the side being anesthetized, then the needle is advanced about 2.5 mm and the

solution is deposited. This is a modification of IANB (the indirect technique) [8].

to transient paralysis of the facial nerve [1].

**Figure 3.** The Inferior Alveolar Nerve Block

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approximately 5 to 10 mm above the previous site.

technique or PDL injection should be done [1].

solve the problem [9].

**2.** The bone is not contacted after 30 mm of needle insertion: the needle should be withdrawn halfway back then the barrel of the syringe is swung over the molar teeth of the opposite side being anesthetized, and then advanced to touch the bone and then continued as described. When the bone is not touched the solution should not be deposited because the needle could be in the parotid gland near the facial nerve and an injection there could lead

One of the most common causes of failure of IANB is depositing the solution too low (below the mandibular foramen) in this case it can be corrected by re-injecting at a higher site,

Mylohyoid nerve is the most common nerve which provides mandible teeth with accessory sensory innervation (most commonly the mesial portion of mandibular first molar). A supplemental injection at the apical region of the tooth in question on the lingual side will

Incomplete anesthesia of the central and lateral incisors is due to overlapping fibers of the contralateral inferior alveolar nerve. In this case a supplemental injection with infiltration In 1973, George Albert Edwards Gow-Gates described a new approach to mandibular anesthesia which he had experience with and reported a success rate of 99% [13]. In this technique the anesthesia solution is deposited on the medial side of the condylar neck just below the insertion of the lateral pterygoid muscles and truly anesthetizes the entire distribu‐ tion of V3, including the inferior alveolar, lingual, mylohyoid, mental, incisive, auriculotem‐ poral and buccal nerves (in 75% of patients). The Gow-gates technique has a higher success rate and a lower incidence of positive aspiration in comparison to IANB.

In this technique the patient is positioned supine or semisupine and is asked to open his mouth widely, then the syringe, fitted with a long needle, is introduced into the mouth through the corner of the mouth on the opposite side. Insertion point is distal to the second molar and in a height of the mesiopalatal cusp of the second molar. The needle is inserted into the tissue and aligned with the plane extending from the corner of the mouth on the opposite side to the intertragus notch on the side of injection, then advanced about 25mm (two third of the needle) until the bone is touched. Then it is withdrawn about 1mm and after negative aspiration in two directions about 1.8 ml of the solution is deposited. If the bone is not contacted, either the patient has partially closed his mouth or the needle is deflected medially (most common cause). In this situation ask the patient to hold his mouth completely open and after withdrawing the needle half way realign the needle anteriorly by swinging the barrel of the syringe somewhat more distally and then advance the needle to contact the bone and continue the process of anesthesia [1, 9](Figure 4).

Due to greater diameter of the mandibular nerve it may require a larger volume of the anesthesia solution, so if the depth of the anesthesia is inadequate after the first injection deposit up to 1.8 ml in the second injection [9].

**Figure 4.** The Gow-Gates technique

### **3.4. Buccal nerve block**

tion of V3, including the inferior alveolar, lingual, mylohyoid, mental, incisive, auriculotem‐ poral and buccal nerves (in 75% of patients). The Gow-gates technique has a higher success

In this technique the patient is positioned supine or semisupine and is asked to open his mouth widely, then the syringe, fitted with a long needle, is introduced into the mouth through the corner of the mouth on the opposite side. Insertion point is distal to the second molar and in a height of the mesiopalatal cusp of the second molar. The needle is inserted into the tissue and aligned with the plane extending from the corner of the mouth on the opposite side to the intertragus notch on the side of injection, then advanced about 25mm (two third of the needle) until the bone is touched. Then it is withdrawn about 1mm and after negative aspiration in two directions about 1.8 ml of the solution is deposited. If the bone is not contacted, either the patient has partially closed his mouth or the needle is deflected medially (most common cause). In this situation ask the patient to hold his mouth completely open and after withdrawing the needle half way realign the needle anteriorly by swinging the barrel of the syringe somewhat more distally and then advance the needle to contact the bone and continue the process of

Due to greater diameter of the mandibular nerve it may require a larger volume of the anesthesia solution, so if the depth of the anesthesia is inadequate after the first injection

rate and a lower incidence of positive aspiration in comparison to IANB.

anesthesia [1, 9](Figure 4).

**Figure 4.** The Gow-Gates technique

deposit up to 1.8 ml in the second injection [9].

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The buccal nerve provides sensory innervation to the buccal gingiva, mucosa and part of the cheek in mandibular molar region. This nerve is consequently not anesthetized during IANB, so if required this nerve most be separately anesthetized. Because the buccal nerve lies immediately beneath the mucous membrane it can be anesthetized easily by depositing about 0.5ml of solution at the coronoid notch (the area distal and buccal to the last molar in the arch). And this nerve block has a success rate of approximately 100% [9].

### **3.5. Mental and incisive nerve block**

The mental nerve and incisive nerve are the terminal branches of the inferior alveolar nerve and provide sensory innervation to the buccal soft tissues lying anterior to the foramen and the soft tissues of the lower lip and chin and those teeth located anterior to the foramen (premolar, canine and incisors) on the injection side. To administer this technique the mental foramen should be located with finger palpation near the apex of the second premolar. The bone immediately around the foramen is rougher to the touch and the patient might feel some soreness when you press your finger against the mental nerve. The needle bevel should be directed toward the bone and the mucosa is penetrated near the mucobuccal fold and the needle is advanced until it reaches the mental foramen, then about 0.6 ml of solution (one third of a cartridge) is deposited. After injection the tissue should be massaged to facilitate entry of the solution into the mental foramen. In the early literature it was emphasized to enter the foramen for a successful nerve block but now it has been shown that this action is completely unnecessary and only increases the risk of damaging the nerve or vessels of the area. Bilateral mental block is very useful when procedures are to be done on anterior or premolar teeth on both sides. [1]
