Dental Anatomy Quiz - Mandibular Nerve Supply

Mandibular Nerve (V3)

• Largest division of the trigeminal nerve, only mixed nerve
• Possesses large sensory root & small motor root
• In the foramen ovale, both roots join to form the nerve trunk
• Leaves the skull and enters the infratemporal fossa
• After leaving the skull, the mandibular trunk has 2 branches:
  • Nervus spinosus (sensory): exits the skull through the foramen spinosum to supply mastoid air cells & dura mater of the middle cranial fossa
  • Nerve to medial pterygoid (motor): supplies medial pterygoid, tensor palati, & tensor tympani muscles
• Nerve trunk is short (2-3mm) and divides into small anterior & large posterior divisions

Branches of Anterior Division

• Three motor branches & one sensory branch
  • Nerve to temporalis
  • Nerve to masseter
  • Nerve to lateral pterygoid
  • Long buccal nerve: crosses the anterior border of the ramus; supplies skin of the cheek, buccal mucoperiosteum of lower molars, and mucobuccal fold

Branches of Posterior Division

• Three sensory & one motor branches
  • Auriculotemporal nerve: arises by 2 roots, surrounds the middle meningeal artery & passes deep to the condylar neck; then runs upwards behind the condyle, crossing the root of zygomatic arch in company with the superficial temporal artery
    • Gives branches to external auditory meatus, innervating skin over meatus & tympanic membrane
    • Articular branch to TMJ
    • Temporal branch supplies skin over temporal area
    • Auricular branch supplies skin over helix & tragus
    • Communicates with otic ganglion to provide parasympathetic fibers to parotid gland

Lingual Nerve

• In infratemporal fossa, joins chorda tympani (facial nerve branch)
• Carries taste fibers to anterior 2/3 of tongue & parasympathetic fibers to submandibular & sublingual salivary glands
• In submandibular region:
  • Lies in pterygomandibular space (between ramus & medial pterygoid muscle)
  • Runs 1 cm anterior, medial, & parallel to inferior alveolar nerve
  • Descends to cross posterior end of mylohyoid line, medial to 3rd molar; passes on superficial surface of hyoglossus muscle

Inferior Alveolar Nerve (IAN)

• Lies posterior & lateral to lingual nerve
• In region between sphenomandibular ligament & medial surface of ramus; enters the mandibular foramen
• Runs in mandibular canal; accompanied by inferior alveolar vessels
• Branches: mylohyoid nerve, branches to mandibular teeth, terminal branches (mental nerve, incisive nerve)
• Mylohyoid nerve (mixed n.): prior to entering the mandibular canal, gives mylohyoid n.; supplies mylohyoid & anterior belly of digastric muscles (motor supply); skin on mental protuberance (sensory). Can give extra pulp innervation to lower molars in some people

Innervation of Teeth

• Table showing the nerves that innervate various teeth (maxillary & mandibular) and their related structures (Pulp, bone, buccal mucoperiosteum, palatal mucoperiosteum, lingual mucoperiosteum)

Accessory Innervation

• Labial mucoperiosteum: might receive additional supply from contralateral side, but infiltration anesthesia does not cause patient pain
• Buccal mucoperiosteum of lower premolars: cutaneous colli nerve (C2 & C3) branches from cervical plexus might supply this area, and can be the cause for pain when IANB is successful

Pulp of Lower 6/7/8

• Sensory fibers from mylohyoid nerve can supply pulp of lower molars; can also reach anterior teeth; can be blocked by lingual infiltration

Bifid Inferior Alveolar nerve

• Two inferior alveolar nerves; one enters mandible through foramen in retromolar area, supplying pulp of lower 8; can be blocked by infiltration

Mandibular Anesthetic Techniques

• More difficult than maxillary techniques due to anatomic variations & need for deeper soft tissue penetration
• Infiltration techniques used for lower anterior teeth & all mandibular teeth of children
• Lower posterior teeth of adults anesthetized by nerve block, as IAN are in canals surrounded by dense cortical bone

For Lower teeth Anesthesia

• Use of incisive nerve (branch of IAN); supplies pulp, bone, & labial mucoperiosteum, & lingual nerve: supplies lingual mucoperiosteum
• Lower premolars: anesthetize using IAN, mental nerve & lingual nerve; supplying pulp/bone & buccal/lingual mucoperiosteum
• Lower molars: anesthetize using IAN; supplying pulp/bone, long buccal nerve: buccal mucoperiosteum, and lingual nerve: lingual mucoperiosteum.

Types of Anesthetic Block techniques

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

Applied Anatomy and Inferior Alveolar Nerve Block

• 2 primary intraoral structures: Pterygomandibular space, Mandibular Foramen site

Pterygomandibular space

• Structure in the pterygomandibular space has significant impact for IANB effectiveness and safety.
• It is a small cleft between the medial pterygoid (medially) and the medial surface of the ramus (laterally)
• Contains: the IAN, artery, vein, nerve to mylohyoid, and sphenomandibular ligament
• Mandibular foramen: located halfway, centered between superior & inferior borders of mandible; 2/3-3/4 from anterior border of ramus to its posterior border

Procedure

• Retro-molar area palpated first, then site of lower 8 (if extracted or unerupted) considered.

• 3 structures needed for successful IANB: -Pterygomandibular raphe (seen) -Deepest portion of the external oblique ridge -Internal oblique ridge

• Steps: -Patient opens mouth widely -Palpate deepest area of EOR with index finger on right and thumb on left -Move finger from molar area up to coronoid process. The deepest area is used as the injection point height. It is 6-10mm above the occlusal plane.

• Rotate finger to midline, palpating IOR.

• Do not insert needle unless IOR is palpated.

• Once IOR is found, retract finger slightly to palpate only its tip and position // to lower occlusal plane.

• Maintain this position maintaining the tissues.

• Syringe with barrel 5mm away from fingertip

• Needle inserted superior to lingula, 6-10mm above the occlusal plane.

• Ensure needle reaches bone at depth of 20-25mm.

• Aspirate (negative pressure: no contact with blood vessels) in two planes.

• Insert 2/3 cartridge, withdraw 1cm, then re-inject remaining 1/3 of cartridge.

• Withdraw syringe slowly, return patient to upright or semi-supine position

• Wait 3-5 mins before testing anesthesia

Infection or Acute Inflammation

• Rare contraindication, but usually a local area around injection site
• May be a cause for complications from IANB

Safety Features

• Needle must contact bone to prevent over-insertion and its complications. Must not surpass a depth of 25mm.

Injection Errors

• High Injection: Syringe directed upward, causing ear numbness from auriculotemporal nerve, trismus from lateral pterygoid, and toxicity from pterygoid plexus of veins.
• Low Injection: Needle directed downward, causing trismus from medial pterygoid, and toxicity from posterior facial vein.
• Early Touch: Needle inserted too laterally, causing incorrect insertion distance between finger and site (< 5mm).
• No bony contact: Distance > 5mm, incorrect angle of insertion, and needle not perpendicular to ramus; needle in posterior lobe of parotid, causing no anesthesia.

Complications

• Hematoma: Swelling on medial side of ramus–Apply pressure, ice for 3-5 minutes
• Trismus: Limited jaw movement due to muscle spasm, common after IANB; slight soreness during mandible opening.
• Transient facial paralysis: Facial nerve (motor nerve to facial expression muscles) can be blocked in the parotid lobe causing inability to close the eye, raise the eyebrow, blow the check, drooping of the lip, or deviation to the other side.

Lefthanded Operator

• Must follow the same rules but with opposite side
• For left side of patient, operator stands in front at 8 o'clock

Patient Positions

• Semi-supine or supine. Never upright to avoid fainting.
• Mouth fully opened for better vision and accessibility.
• Operator on right side of patient (8 o'clock); index finger used for palpation of coronoid notch.

Test your knowledge on the anatomy and function of mandibular nerve supplies in dental procedures. This quiz covers aspects like the fibers of the otic ganglion, the relationship between various nerves, and techniques for administering anesthesia effectively. Perfect for dental students and professionals looking to reinforce their understanding of mandibular innervation.