Mandibular Anesthesia Techniques

Mandibular Nerve (V3)

• The mandibular nerve is the largest division of the trigeminal nerve, and the only mixed nerve (sensory and motor).
• It has both a large sensory root and a small motor root.
• The sensory and motor roots join within the foramen ovale to form the nerve trunk.
• The nerve trunk leaves the skull and enters the infratemporal fossa.
• The mandibular trunk gives off two branches:
  • Nervus spinosus (sensory): This branch exits the skull through the foramen spinosum to supply mastoid air cells and dura mater of the middle cranial fossa.
  • Nerve to medial pterygoid (motor): This branch supplies the medial pterygoid, tensor palati, and tensor tympani muscles.
• The nerve trunk is short (2-3mm) and divides into anterior and posterior divisions.

Branches of Anterior Division

• The anterior division has three motor branches and one sensory branch.
• Three motor branches supply the temporalis, masseter, and lateral pterygoid muscles.
• The sensory branch is the long buccal nerve, supplying the skin of the cheek, buccal mucoperiosteum of lower molars, and mucobuccal fold.

Branches of Posterior Division

• The posterior division has three sensory branches and one motor branch.
• Auriculotemporal nerve, which arises from two roots surrounding the middle meningeal artery, passes deep to the condylar neck, then upward behind the condyle crossing the zygomatic arch with the superficial temporal artery.
• It provides branches to the external auditory meatus, tympanic membrane, TMJ, skin over temporal areas, helix, and tragus and provides parasympathetic secretory fibers to the parotid gland.

Lingual Nerve

• The lingual nerve runs through the infratemporal fossa, then the submandibular region.
• In the infratemporal fossa, it joins the chorda tympani (branch of facial nerve) and carries taste fibers to the anterior two-thirds of the tongue, and parasympathetic secretory fibers to the submandibular and sublingual salivary glands.
• In the submandibular region, it lies within the pterygomandibular space (between ramus and medial pterygoid muscle).
• It runs alongside the inferior alveolar nerve.
• It crosses the posterior end of the mylohyoid line, then to the medial surface of the third molar, before moving to the superficial surface of the hyoglossus muscle.

Inferior Alveolar Nerve (IAN)

• The IAN lies posterior and lateral to the lingual nerve, in the region between the sphenomandibular ligament and the medial surface of the ramus.
• It enters the mandibular foramen to run in the mandibular canal, accompanied by inferior alveolar vessels.
• It gives off the mylohyoid nerve (mixed), which supplies the mylohyoid and anterior belly of the digastric muscles (motor) and the skin over the mental protuberance (sensory).
• Branches to all mandibular teeth;
• Mental nerve supplying skin over the chin, lower lip, and buccal mucoperiosteum of the premolar region.
• Incisive nerve supplying the anterior teeth.

Innervation of Teeth

• The innervation of different teeth is determined by the respective nerve supplying them (maxillary or mandibular area).

Accessory Innervation

• Labial mucoperiosteum of upper and lower centrals may receive additional supply from the opposite side.
• Buccal mucoperiosteum of lower premolars can receive supply from the cervical plexus of nerves.

Pulp of Lower 6,7,8

• Sensory fibers from the mylohyoid nerve may supply the pulp of lower molars, which can reach the anterior teeth.
• This innervation is blocked by lingual infiltration.

Bifid Inferior Alveolar

• There are two inferior alveolar nerves, one of which enters the mandible through foramina in the retromolar area. These nerves supply the pulp of the lower 8th tooth and are blocked by infiltration.

Mandibular Anesthetic Techniques

• Mandibular anesthesia techniques are more complex than maxillary techniques due to greater anatomic variation in the mandible and the need for deeper soft tissue penetration.
• Infiltration techniques are used to anesthetize lower anterior teeth and all mandibular teeth in children.
• For lower posterior teeth in adults, a nerve block is used because the inferior alveolar nerve lies in a canal surrounded by dense cortical bone.

Nerves Anesthetized and Areas Anesthetized (Inferior Alveolar Nerve Block)

• Inferior alveolar nerve (IAN) and its terminal branches (incisive and mental nerves).
• Lingual nerve.
• This block anesthetizes the mandibular teeth, body of the mandible, lower portion of the ramus, buccal mucoperiosteum anterior to the mental foramen, anterior two-thirds of the tongue and floor of the mouth, lingual mucoperiosteum of all lower teeth, the lower lip and chin on the injected side.

Types of Anesthetic Block Techniques

• IAN and lingual nerve are anesthetized using IAN block, Vazirani-Akinosi mandibular nerve block, or Gow-Gates nerve block
• Mental nerve is anesthetized by a mental nerve block.
• Incisive nerve is anesthetized by an incisive nerve block.
• Long buccal nerve is anesthetized by long buccal infiltration, long buccal nerve block, or Gow-Gates nerve block.

Pterygomandibular Space

• Two major intraoral anatomical structures considered in inferior alveolar nerve block procedures.
  • Pterygomandibular space (needle insertion area).
  • Mandibular foramen site.
• It's a small cleft between the medial pterygoid and medial surface of the ramus.
• The space contains the inferior alveolar nerve, artery, vein, nerve to mylohyoid, and sphenomandibular ligament.
• The lingual nerve, located laterally to the IAN, is positioned 1 cm anterior and medial.

Procedure

• Palpate the retro-molar area, which is distal to the lower 8th tooth.
• Locate the pterygomandibular raphe, deepest portion of the external oblique ridge (EOR), and internal oblique ridge (IOR).
• The IAN is located midway between the IOR and lingula, and the needle insertion point is at the height of the deepest EOR.

Patient Position

• The patient should be in a semi-supine or supine position to avoid fainting and to maximise visibility.
• With the mouth open wide, to improve visibility and accessibility for injection.

Steps

• Open the patient's mouth widely and locate the raphe
• Using index finger on the right side and thumb on the left, palpate the deepest portion of EOR and gradually move it to the coronoid
• Stop when the deepest part of EOR is found.
• Rotate the finger towards the midline across the retromolar area to locate the IOR
• Position the needle parallel to the lower occlusal plane at the height of the IOR.

Injection Errors

• High injection: syringe barrel directed upward can lead to ear numbness (auriculotemporal nerve), trismus (lateral pterygoid), toxicity (pterygoid plexus).

• Low injection: syringe barrel directed downward can cause trismus (medial pterygoid), toxicity (posterior facial vein), and early touch (if the needle insertion is too lateral).

• No bony contact: if the distance from the finger to the insertion point is more than 5mm and the needle is not perpendicular to the ramus, there's a chance of incorrect LA deposition into the parotid gland posterior lobe.

Signs and Symptoms

• Tingling, numbness, or swelling of the lower lip suggests mental nerve anesthesia.
• Tingling or numbness of the tongue suggests lingual nerve anesthesia.
• No pain during probing.

Complications

• Hematoma (rare).
• Trismus.
• Transient facial palsy (facial nerve paralysis).

This quiz explores the complexities of mandibular anesthetic techniques compared to maxillary approaches. It covers the specific nerves involved, the anatomy relevant to lower teeth anesthesia, and the roles of various nerve blocks. Test your knowledge on the intricacies of dental anesthesia.