**2. Modified mental incisive nerve block technique**

#### **2.1. Overview**

**•** The mental-incisive nerve block can be used where lower premolars and anterior teeth require treatment. In this chapter we present our method of mental-incisive nerve block for extraction of the lower premolars and anterior teeth or dentoalveolar surgery.


#### **2.2. Background**

The Inferior Alveolar Nerve Block (IANB) is the most important injection technique in dentistry. Unfortunately it also proves to be the most frustrating; with the highest percentage of clinical failure [6]. Potocnik and Bajrovic reported that even when a proper technique is employed, clinical studies show that IANB fails in approximately 30% to 45% of cases [7]. When dental treatment involved procedures on mandibular premolars and anterior teeth the incisive nerve block can be administered with greater success [6]. However, the injection technique for mental-incisive nerve block (MINB) may also influence the success rate.

#### **2.3. Clinical anatomy**

The level of anesthesia obtained by our method in the anterior palate is satisfactory. The labial infiltration method resulted in total anesthesia in the majority of the cases. Failures may be the result of anatomic and physiologic variations. An eight minute wait or longer may be more effective than five minutes following the second injection. The amount of pain experienced by the patients during the injection in the labial infiltration approach is less than the conventional

**Figure 5.** Needle inserted superior to the apices of central incisors in the vicinity of the superior border of the base of the anterior nasal spine near the nasal floor at a 45 degree angle to the long axis of the central incisor, to obtain anes‐

**Figure 4.** The anesthesia of the maxillary hard and soft tissue of the labial area is obtained by injection of 1 cc of local anesthetic agent, with the syringe parallel to the long axis of the tooth. Orient the needle bevel toward the bone.

**•** The mental-incisive nerve block can be used where lower premolars and anterior teeth require treatment. In this chapter we present our method of mental-incisive nerve block for

extraction of the lower premolars and anterior teeth or dentoalveolar surgery.

**2. Modified mental incisive nerve block technique**

approach in most cases. [5]

thesia in the anterior palate.

58 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**2.1. Overview**

The target is the mental foramen located on external surface of the body of the mandible below the first and second premolars where the IAN divides into terminal (incisive and mental) branches. The incisive branch continues forward in a bony canal or in a plexiform arrangement, giving off branches to the first premolar, canine and incisor teeth, and the associated labial gingiva. The lower central incisor teeth receive a bilateral innervation, fibers probably cross the midline within the periosteum to re-enter the bone via numerous canals in the labial cortical plate. The mental nerve passes upward, backward and outward to emerge from the mandible via the mental foramen between and just below the apices of the premolar teeth [8].

**Figure 6.** In 24% of individuals the mental foramen is located distal to the root of the second premolar; in 20 to 25%, between the premolars roots, in 50% at the site of the second premolar root and in 1% to 2% anterior to the first premo‐ lar or mesial to the first molar.

However, the location of mental foramen varies in different people [8-13]; in 24% of individuals the mental foramen is located distal to the root of the second premolar; in 20 to 25%, between the premolars roots, in 50% at the area of the second premolar root and in 1% to 2% anterior to the first premolar or mesial to the first molar (Figure 6). [13] This variability in location may cause problems in obtaining anesthesia [8, 10, 13-15].

### **2.4. Technique**

There are different methods for MINB; the authors compared 2 mental–incisive nerve block techniques for the extraction of lower premolars and anterior teeth bilaterally. One method was to inject between the first and second premolar so that the needle passed between the two premolars vertically. In the other method, the injection was performed distal to the second premolar.

This randomized double blind, split-mouth clinical study was done; in the case group, the needle penetrated the depth of the vestibule distal to the second premolar using a 27 gauge needle. Entry was from behind the patient at the ten O' clock and the opposite side at the 2 O' clock position. The needle entered the soft tissue about 5-8 mm supraperiosteal, with mouth half-open and lip and buccal tissues retracted. When standing behind the patient, the ana‐ tomical landmarks were the second premolar and buccal vestibule (Figure 7).

**Figure 7.** The injection administered distal to the second premolar. The syringe should be from posterior to anterior, from above to below and from lateral to medial while standing behind the patient.

In the control group an injection was done in the depth of buccal mucosa between two premolars at a depth of 5-6 mm using a 27 gauge needle with the mouth half open standing behind the patient (Figure 8). [16]

In both groups the local anesthetic solution was lidocaine 2% (1 cc) with epinephrine (1/80000). It is not necessary for the needle to enter the mental foramen. Data was statistically analyzed using the chi-square test. All patients had a lingual injection (0.5 cc) which was administered 5 mm distal to the tooth in the floor of the mouth.

The MINB with needle entrance distal to the second premolar from behind had a 95% success rate and MINB with needle entrance between premolars had a 72.5% success rate respectively

**Figure 8.** The injection administered in the depth of buccal mucosa between two premolars at a depth of 5-6 mm using a 27 gauge short needle with the mouth half open while standing behind the patient.

(p<0.01). Thus, if the mental nerve block injection is administered with the needle entrance between premolars, the chance of failure is greater (R.R=5.5).

#### **2.5. Discussion**

However, the location of mental foramen varies in different people [8-13]; in 24% of individuals the mental foramen is located distal to the root of the second premolar; in 20 to 25%, between the premolars roots, in 50% at the area of the second premolar root and in 1% to 2% anterior to the first premolar or mesial to the first molar (Figure 6). [13] This variability in location may

There are different methods for MINB; the authors compared 2 mental–incisive nerve block techniques for the extraction of lower premolars and anterior teeth bilaterally. One method was to inject between the first and second premolar so that the needle passed between the two premolars vertically. In the other method, the injection was performed distal to the second

This randomized double blind, split-mouth clinical study was done; in the case group, the needle penetrated the depth of the vestibule distal to the second premolar using a 27 gauge needle. Entry was from behind the patient at the ten O' clock and the opposite side at the 2 O' clock position. The needle entered the soft tissue about 5-8 mm supraperiosteal, with mouth half-open and lip and buccal tissues retracted. When standing behind the patient, the ana‐

**Figure 7.** The injection administered distal to the second premolar. The syringe should be from posterior to anterior,

In the control group an injection was done in the depth of buccal mucosa between two premolars at a depth of 5-6 mm using a 27 gauge needle with the mouth half open standing

In both groups the local anesthetic solution was lidocaine 2% (1 cc) with epinephrine (1/80000). It is not necessary for the needle to enter the mental foramen. Data was statistically analyzed using the chi-square test. All patients had a lingual injection (0.5 cc) which was administered

The MINB with needle entrance distal to the second premolar from behind had a 95% success rate and MINB with needle entrance between premolars had a 72.5% success rate respectively

from above to below and from lateral to medial while standing behind the patient.

behind the patient (Figure 8). [16]

5 mm distal to the tooth in the floor of the mouth.

tomical landmarks were the second premolar and buccal vestibule (Figure 7).

cause problems in obtaining anesthesia [8, 10, 13-15].

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**2.4. Technique**

premolar.

The MINB can be an alternative to the IANB when dental procedures requiring pulpal anesthesia on mandibular teeth anterior to the mental foramen (e.g. canine to canine or premolar to premolar) are treated. According to the result, we found that MINB with needle penetration distal to second premolar was more effective (95%) than injection between two premolars (72.5%). Al Yasser and Al Nwoku [15] showed that the mental foramen location on both sides of the mandible in 80% of cases is symmetrical and in 46.2% of cases the mental foramen is located between the longitudinal axes of the two premolars. Moiseiwitch [10] reported that anterior-posterior positions of mental foramens in most cases are symmetrical. In most studies on mental foramens in different cases, researchers reported that most mental foramens are in line with second premolars [11, 14]. What most scientists agree with is the presence of mental foramen in range of the long axis of the second premolar [10-12] with about 50% of cases at the level of the root of second premolar, between the two premolars in about 20% to 25% and posterior to the second premolar in about 24%, and in approximately 1% to 2% it lies as forward as the first premolar or as far back as the first molar [13]. This may be why the technique in which the needle penetrates mucosa distal to second premolar may yield the success rate of MINB higher. According to the results, the success rate of anesthesia adminis‐ tered distal to second premolar was 95% and with needle penetration between premolar was 72.5% [6, 9]. According to Malamed the correct position of the dentist is in front of the patient so that the syringe may be placed into the mouth below the patients line of sight and the thumb or index finger in the mucobuccal fold against the body of the mandible in the first molar area and moved slowly anteriorly until feeling the bone become irregular and somewhat concave [6] while in our technique there is no need to palpate the area and produce discomfort for patients. Mucosal penetration done from the distal of the second premolar hides the needle from the line of sight of the patient. When standing in front of the patient it is easier for the patient to see the needle whereas when standing behind the patient it is unlikely for him or her to visualize the needle. [17]

#### **2.6. Conclusion**

Mental-incisive nerve block injection distal to the second premolar from behind the patient was more successful than between premolars from the front.
