• Also referred to as - Mandibular nerve block.
• Nerves anesthetized- 1. inferior alveolar, a branch of the posterior division of the mandibular division
of the trigeminal nerve (V3). 2. incisive nerve . 3. mental nerve . 4. lingual (commonly).
• Areas anesthetized – 1. mandibular teeth to the midline , 2. body of the mandible ,inferior portion of
the ramus , 3. buccal mucoperiosteum , mucous membrane anterior to the mental foramen (mental
nerve)., 4. anterior two-thirds of the tongue and floor of the oral cavity (lingual nerve). , 5. lingual soft
tissues and periosteum (lingual nerve).
• Indications – procedures on multiple mandibular teeth in one quadrant , when buccal soft tissue
anesthesia (anterior to the mental foramen ) is necessary , when lingual soft tissue anesthesia is
• Contraindications- infection or acute inflammation in the area of injection , patients who are more
likely to bite their lip or tongue, for instance , a very young child or a physically or mentally
handicapped adult or child.
• Advantages- one injection provides a wide area of anesthesia (useful for quadrant dentistry).
• Disadvantages – wide area of anesthesia (not indicated for localized procedures) , rate of inadequate
anesthesia (31% to 81%), intraoral landmarks not consistently reliable, positive aspiration (10% to 15%,
highest of all intraoral injection techniques ), lingual and lower lip anesthesia , discomfiting to many
patients and possibly dangerous (self- inflicted soft tissue trauma ) for certain individuals, partial
anesthesia possible where a bifid inferior alveolar nerve and bifid mandibular canals are present ;
cross-innervation in lower anterior region.
• Positive aspiration – 10% to 15%.
• Alternatives – mental nerve block, for buccal soft tissue anesthesia anterior to the first molar , incisive
nerve block , for pulpal and buccal soft tissue anesthesia of teeth anterior to the mental foramen
(usually second premolar to central incisor ), superaperiosteal injection , for pulpal anesthesia of the
central and lateral incisors and sometimes the premolars and molars , Gow-Gates mandibular nerve
block ,Vazirani – Akinosi mandibular neve block , PDL injection for pulpal anesthesia of any mandibular
tooth, IO injection for pulpal and soft tissue anesthesia of any mandibular tooth, but especially molars.
• Technique – 25-gauge long needle is preferred; a 27 gauge long is acceptable.
• Area of insertion – mucous membrane on the medial (lingual) side of the mandibular ramus, at the
intersection of two lines – one horizontal , representing the height of needle insertion , the other
vertical , representing the anteroposterior plane of injection.
• Target area – inferior alveolar nerve as it passes downward toward the mandibular foramen but
before it enters into the foramen.
• Landmarks – a. coronoid notch (greatest concavity on the anterior border of the ramus), b.
pterygomandibular raphe (vertical portion), c. occlusal plane of the mandibular posterior teeth.
• Orientation of the needle bevel – less critical than with other nerve blocks, because the needle
approaches the inferior alveolar nerve at roughly a right angle.
• Procedure- a. for a right IANB, a right-handed administrator should sit at the 8 o’clock position facing
the patient , b. for a left IANB , a right –handed should sit at the 10 o’clock position facing in the same
direction as the patient.
• Three parameters must be considered during administration of IANB : 1) the height of the injection ,
(2) the anteroposterior placement of the needle (which helps to locate a precise needle entry point ),
and (3) the depth of penetration (which determines the location of the inferior alveolar nerve).
• Aspirate in 2 planes . If negative, slowly deposit 1.5 mL of anesthetic over a minimum of 60 seconds
.(because of the high incidence of positive aspiration and natural tendency to deposit solution too
rapidly , the sequence of slow injection, reaspiration, slow injection, reaspiration is strongly
• Slowly withdraw the syringe , and when approximately half its length remains within tissues,
approximately half its length remains within tissues, reaspirate . If negative , deposit a portion of the
remaining solution (0.2 mL) to anesthesia the lingual nerve .
• Signs and symptoms – 1. subjective – tingling or numbness of the lower lip indicates anesthesia of the
mental nerve , a terminal branch of the inferior alveolar nerve .This is a good indication that the
inferior alveolar nerve is anesthetized , although it is not a reliable indicator of the depth of anesthesia,
tingling or numbness of the tongue indicates anesthesia of the lingual nerve, a branch of the posterior
division ofV3. it usually accompanies IANB but may be present without anesthesia of the inferior
alveolar nerve .
• Objective – using an electrical pulp tester (EPT) and eliciting no response to maximal output (80/80)
on two consecutive tests at least 2 minutes apart serves as a “guarantee” of successful pulpal
anesthesia in nonpulpitic teeth, no pain is felt during dental therapy.
• Safety feature – the needle contacts bone, preventing over – insertion with its attendant
• Precautions- 1. donot deposit local anesthetic if bone is not contacted , needle tip may be
resting within the parotid gland near the facial nerve (cranial nerveVII), and a transient
blockade (paralysis) of the facial nerve may develop if local anesthetic solution is deposited.
• 2. avoid pain by not contacting bone too forcefully.
• Failures of anesthesia – the most common causes of absent or incomplete IANB – deposition
of anesthetic too low (below the mandibular foramen) , deposition of the anesthetic too far
anteriorly (laterally) on the ramus , accessory innervation to the mandibular teeth, incomplete
anesthesia of the central or lateral incisors.
• Complications – hematoma , trismus , transient facial paralysis (facial nerve anesthesia).
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