anesthesia pt1

Learning Objectives

• Define & correctly pronounce key terminologies and anatomic names in the chapter
• Identify tissues/structures anesthetized by every local-anesthetic injection; describe related target areas
• Locate & name anatomic landmarks used to determine each needle-insertion site on skull and patient
• Demonstrate proper needle placement for all injections on skull & patient
• Recognize tissues penetrated during needle insertion
• Discuss (1) signs of clinically effective anesthesia and (2) complications linked to anatomy for every injection
• Integrate knowledge of trigeminal-nerve anatomy with clinical administration of local anesthetics in dentistry
• Use companion Evolve website for additional practice

General Anatomic & Clinical Considerations

• Successful pain control demands precise knowledge of skull, trigeminal nerve, vascular & glandular anatomy
• Hard-tissue landmarks (maxilla, palatine bone, mandible) are more reliable than soft-tissue topography (which varies among patients)
• Adjacent critical structures (major blood vessels, glands) must be avoided → aspiration on multiple planes is mandatory to confirm needle tip position
• Strict infection-control prevents needle-tract contamination & deeper-tissue spread
• Trigeminal (CN V) provides sensory input to teeth; clinically, maxillary & mandibular divisions are routinely anesthetized
• Vasoconstrictor-containing solutions also provide hemostasis & lengthen anesthesia duration

Injection Types

• Nerve block
  • Deposition near larger nerve trunks → broader region anesthetized (multiple teeth/quadrant)
  • Works even if localized infection exists (deposit distant from site)
  • Fewer punctures & smaller total volume for a quadrant
• Supraperiosteal injection
  • Deposits near terminal branches at tooth apex
  • Typically 1 tooth affected; effectiveness lowered by bone thickness or local infection
  • Needs additional volume & multiple sticks for a quadrant

Dosage & Tooth/Bone Variations

• Underdosing ⇒ incomplete anesthesia, esp. in patients with large teeth, long roots, or unusually thick alveolar bone
• Use only the minimal volume that achieves full clinical effect

Sequencing & Infection Rules

• Never inject through abscess, cellulitis, osteomyelitis (risk of spreading odontogenic infection)
• Anesthetic efficacy drops in infected tissues → if extra volume required, still comply with maximum recommended dosage
• Quadrant dentistry: give injections posterior → anterior; start treatment posterior → anterior

Comparative Bone Density

• Maxillary facial cortical plate = thinner, more porous than mandibular → easier, more predictable anesthesia
• Fewer anatomic variations in maxilla/palatine bone & nerves → troubleshooting seldom needed

Overview of Common Dental Nerve Blocks (Fig 9.1)

• Maxilla: Infraorbital (IO), Anterior Superior Alveolar (ASA), Middle Superior Alveolar (MSA), Posterior Superior Alveolar (PSA), Nasopalatine (NP), Greater Palatine (GP)
• Mandible: Inferior Alveolar (IA), Incisive (IN)/Mental, (Long) Buccal, Gow-Gates (GG), Vazirani-Akinosi (VA)

Gow-Gates Mandibular Block (Table 9.3)

• Nerves anesthetized: IA, lingual, (long) buccal, mental, incisive, mylohyoid, auriculotemporal
• Teeth: all mandibular teeth to midline
• Other structures: facial & lingual periodontium/gingiva to midline, lower lip, anterior $\tfrac{2}{3}$ tongue, floor of mouth to midline, possible buccal gingiva of molars, skin over zygomatic, posterior buccal & temporal regions

Vazirani-Akinosi Mandibular Block (Table 9.3)

• Nerves: IA, lingual, mental, incisive, mylohyoid
• Teeth: mandibular teeth to midline
• Other structures: lingual gingiva to midline; facial gingiva of anteriors & premolars to midline; probable buccal gingiva of molars; lower lip; anterior $\tfrac{2}{3}$ tongue; floor of mouth

Key Mandibular Landmarks (extract from table)

• Intertragic notch (tragus), contralateral labial commissure, mesiolingual cusp of maxillary 2nd molar
• Coronoid process, pterygomandibular space, medial ramus surface, maxillary tuberosity, maxillary occlusal plane

Maxillary Nerve Anesthesia (General)

• Facial cortical bone thin → high success; palatal approach possible
• Pulpal anesthesia: via superior dental plexus entering apical foramina
• Periodontium/gingiva: interdental & interradicular branches
• Recommended blocks per region
  • PSA → molars (+ buccal gingiva)
  • MSA → premolars ± MB root of 1st molar (if nerve exists; $\approx28\%$)
  • ASA → anterior teeth to midline
  • IO → covers ASA + MSA zones in one injection
  • GP → palatal gingiva of posterior sextant
  • NP → palatal gingiva canine–canine (bilateral)
  • Anterior Middle Superior Alveolar (AMSA) → pulpal + facial + palatal anesthesia canine–canine/posteriors except PSA zone; combine with PSA for full quadrant

Posterior Superior Alveolar (PSA) Block

• Structures anesthetized (typical)
  • Maxillary molars (except MB root of 1st molar in $\approx28\%$)
  • Associated buccal periodontium & gingiva
• Target area
  • PSA nerve branches at PSA foramina on infratemporal surface of maxilla
  • Foramina lie posterosuperior on maxillary tuberosity, superior to 2nd molar apices
• Injection site
  • Height of maxillary mucobuccal fold, superior to 2nd molar apices, distal to zygomatic process
  • Needle advanced distally & medially without bony contact
• Syringe orientation (3 planes, single movement)
  • Superior: $45^\circ$ to maxillary occlusal plane
  • Medial: $45^\circ$ to occlusal plane
  • Posterior: $45^\circ$ to long axis of 2nd molar
  • Barrel usually aligned with ipsilateral labial commissure
• Depth: Current research favors shallower insertion; space still fills with solution, lowering risk
• Positive aspiration risk: high (PSA vessels adjacent) → ALWAYS aspirate
• Possible complications
  • Inadvertent mandibular-nerve anesthesia (lingual, lower lip) if solution placed too lateral
  • Hematoma: over-insertion pierces pterygoid venous plexus or maxillary artery → infra-temporal fossa swelling; bluish-reddish discoloration migrates inferior-anterior on cheek
  • Needle-tract infection → potential cavernous-sinus involvement if contaminated
• Patient communication
  • Little soft-tissue numbness; patient feels “dull” teeth; warn beforehand to avoid anxiety

Middle Superior Alveolar (MSA) Block

• Anesthetizes premolars ± MB root of 1st molar and buccal gingiva if MSA nerve present ($\approx28\%$)
• If MSA nerve absent ($\approx72\%$), PSA & ASA together cover area
• Many clinicians routinely add MSA to ensure 1st-molar coverage (innervation unknown)
• Combine with GP block for palatal gingiva when needed

Clinical Pearls & Troubleshooting

• Do not contact maxilla during PSA; if bone touched immediately on insertion, medial angle > $45^\circ$ → lower barrel closer to occlusal plane
• Practice orientation using long cotton-tipped applicator dipped in topical anesthetic
• Conservative depth = safer without sacrificing efficacy

Ethical & Practical Implications

• Pain control must balance efficacy with patient safety (minimal dose, avoid infected sites, aspirate)
• Understanding variations (nerve absence, bone density) prevents over-medication & repeat injections
• Communication: Explain sensory expectations (e.g., PSA lacks lip/tongue numbness) to reduce fear
• Maintain aseptic technique to protect both patient & operator

Numerical & Angular References

• Maxillary nerve blocks: cortical bone thinner than mandible → radiographically evident
• MSA presence $\approx28\%$, absence $\approx72\%$
• PSA angulations: all $45^\circ$ orientations (superior, medial, posterior)
• Tongue/lip anesthesia: anterior $\tfrac{2}{3}$ of tongue covered in GG & VA

Connections to Previous Chapters/Clinical Anatomy

• Skull osteology (Ch 3): maxillary tuberosity, zygomatic process, palatine bone landmarks
• Soft-tissue palpation (Ch 2) informs initial needle placement
• Vascular anatomy (Ch 6): PSA artery proximity → aspiration importance
• Glandular anatomy (Ch 7): avoid inadvertent gland injection
• Infection pathways (Ch 12): cavernous sinus hazards from contaminated needle tract
• Trigeminal nerve anatomy (Ch 8): sensory branches & dental plexuses supply teeth/gingiva

Quick Reference: Block → Area Covered

• PSA: Molars (+ buccal gingiva)
• MSA: Premolars ± MB root 1M
• ASA: Anteriors to midline
• IO: ASA + MSA zone (anteriors & premolars)
• GP: Palatal gingiva posterior sextant
• NP: Palatal gingiva canine–canine (bilateral)
• AMSA: Pulpal & full soft tissue canine–canine + posteriors except PSA zone
• IA: Mandibular teeth to midline, facial gingiva anteriors+premolars, lingual gingiva all
• Buccal: Buccal gingiva molars only
• IN/Mental: Anterior teeth & premolars (pulp) + facial gingiva/lip
• GG: Entire mandibular quadrant
• VA: Entire mandibular quadrant (closed-mouth approach)

Study & Practice Tips

• Rehearse landmark identification on skull models before moving to patients
• Visualize 3-D anatomy: review panoramic & CBCT images highlighting bone thickness & foramina
• Perform dry runs with cotton applicator to master syringe angulation
• Keep aspirating even after needle repositioning; blood in carpule = reposition & repeat
• Document volumes, needle gauge/length, patient response, and any complications for future reference