Maxillary Nerve Anatomy & PSANB Technique

Maxillary Nerve Anatomy

• Branches within the cranium: middle meningeal nerve
• Branches within the pterygopalatine fossa:
  • Zygomatic nerve: zygomaticotemporal nerve, zygomaticofacial nerve
  • Pterygopalatine nerves: palatine branches (GP & LP nerves), nasal branches (NP nerve), orbital branches, pharyngeal branch
  • Posterior Superior Alveolar (PSA) nerve
• Branches within the infra-orbital canal:
  • Middle Superior Alveolar (MSA) nerve
  • Anterior Superior Alveolar (ASA) nerve
• Branches on the face: inferior palpebral branches, external nasal branches, superior labial branches

Posterior Superior Alveolar Nerve Block (PSANB) Technique

• Also known as Zygomatic Block, Tuberosity Block
• Anesthetizes:
  • PSA nerve
• Areas anesthetized:
  • Buccal mucoperiosteum over maxillary molars
  • Buccal and palatal alveolar plates of bone
  • Periodontium of maxillary molars (except MB root of 1st molar)
  • Pulps of maxillary molars (except MB root of 1st molar)
  • Adjacent lining of the maxillary sinus

PSANB Technique

• Goal: Deposit local anesthetic close to PSA nerves, located posterosuperior and medial to the maxillary tuberosity
• Indications:
  • Treatment involving two+ maxillary molars

PSANB Technique: Needle Insertion

• Landmarks:
  • Mucobuccal fold, distal to the maxillary 2nd molar, slightly above occlusal plane
• Direction:
  • Inward: medially at 45-degree angle towards midline & occlusal plane
  • Upward: superiorly towards the maxillary tuberosity
• Depth:
  • Average Adults: ¾ of short needle length (16 mm)
  • Smaller Adults & Children: ½ of short needle length (10 mm)

PSANB Technique: Injection

• Aspiration test in two perpendicular planes
• Slow deposition of 0.9 ml (half-cartridge) up to 1.8 ml (full-cartridge) of anesthetic solution over 30 – 60 seconds
• Multiple aspirations during injection

PSANB Technique: Post-Injection

• Withdraw needle
• Recapp using single hand scoop technique
• Wait 3 to 5 minutes before treatment

PSANB Technique: Clinical Findings

• Subjective:
  • Tingling and numbness
• Objective:
  • Probing Test: No pain during probing of facial mucosa of maxillary molars
  • Electrical Pulp Tester: No response with maximal EPT output (80/80)
  • Freezing Spray: No response
  • Absence of pain during treatment

PSANB Technique: Advantages

• High success rate (>95%)
• Atraumatic technique (minimal pain):
  • Target area is loose connective tissue
  • No bone contact
• One injection (vs. three infiltrations)
• Minimizes total anesthetic volume

PSANB Technique: Disadvantages

• Risk of diffuse intraoral hematoma in buccal mandibular region
• Arbitrary technique (no bony landmarks)
• Second injection may be required for first molar anesthesia (approximately 30%)

PSANB Technique: Causes of Failures & Complications

• Needle too lateral: Redirect medially
• Needle not high enough: Redirect superiorly
• Needle too far posterior: Withdraw to proper depth

PSANB Technique: Hematoma in Buccal Tissues of Mandibular Region

• Caused by:
  • Inserting needle too far posteriorly
• May result in injury to pterygoid plexus of veins or perforation of maxillary artery

Anterior Superior Alveolar Nerve Block (ASANB) Technique

• Also known as Infraorbital Nerve Block
• Anesthetizes:
  • ASA nerve
  • MSA nerve (present in only 30% of population)
  • Terminal branches of Infraorbital Nerve:
    • Inferior palpebral: Lower eyelid
    • Lateral nasal: Lateral aspect of the nose
    • Superior labial: Upper lip

ASANB Technique: Applied Anatomy

• Anesthetic should enter infraorbital canal through infraorbital foramen

ASANB Technique: Advantages

• High success rate and safe when proper protocol followed

ASANB Technique: Indications

• Dental procedures involving two+ maxillary anterior teeth (incisors through premolars)
• When supraperiosteal injections have been ineffective due to dense bone
• Inflammation or infection (contraindicates supraperiosteal injection)
  • Note: If cellulitis is present, a maxillary nerve block may be indicated instead of ASANB

ASANB Technique: Contraindications

• Severe infection in the region of the injection site
• Facial or orbital cellulitis
• Presence of congenital or acquired anatomical abnormalities
• Patients with hypersensitivity to local anesthetics

ASANB Technique: Intraoral Injection

• Landmarks:
  • Mucobuccal fold, just apical to maxillary canine, between canine and lateral incisor
• Direction:
  • Superiorly: Towards infraorbital foramen, approximately 45-degree angle
• Depth:
  • About 15 mm (half needle length)
• Aspiration:
  • Before and during injection
  • Avoid injecting into blood vessels
• Volume:
  • 0.9 ml (half-cartridge) to 1.2 ml (full-cartridge)
• Wait 3 to 5 minutes before treatment

ASANB Technique: Clinical Findings

• Subjective:
  • Tingling and numbness of ipsilateral lower eyelid, side of nose, upper lip, teeth & soft tissues
• Objective:
  • Probing Test: No pain during probing of facial mucosa
  • Electric Pulp Tester: No response at maximal output
  • Thermal Pulp Test: No response
  • Absence of pain during treatment (e.g., cavity test)

ASANB Technique: Causes of Failures & Correction

• Needle contacting bone inferior to infraorbital foramen:
  • Anesthesia of lower eyelid, side of nose, and upper lip may develop with little or no dental anesthesia
  • Correction: Keep needle in line with infraorbital foramen, estimate depth before injection.
• Needle deviation medially or laterally to infraorbital foramen:
  • Correction: Keep needle orientation toward foramen.

ASANB Technique: Alternative Techniques

• Basic Injection Techniques:
  • Infiltration technique
  • Maxillary Nerve block
• Supplementary Injection Techniques:
  • Periodontal ligament Injection

ASANB Technique: Complications

• Hematoma across the lower eyelid
• Temporary double vision (horizontal diplopia)