anesthesia pt5

Incisive Block (IB)

  • Purpose & Coverage

    • Anesthetizes mental + incisive nerves.
    • Teeth/tissues affected
    • Mandibular anterior teeth + premolars to midline (pulpal + facial periodontium/gingiva).
    • Ipsilateral lower lip & chin.
    • Does NOT anesthetize lingual periodontium/gingiva → supplement with
    • Supraperiosteal (lingual) injection at medial mandibular border, or
    • Inferior-Alveolar (IA) block if wider coverage needed.
    • Employed when
    • Cross-over innervation from contralateral incisive nerve persists after IA block.

  • Anatomical Background

    • Incisive nerve merges with mental nerve inside mental foramen before becoming Inferior Alveolar Nerve (IAN).
    • Mental foramen location
    • Typically inferior to apices of mandibular premolars.
    • Faces postero-superiorly in adults.
    • Radiographic range: as posterior as apex of 1st molar or as anterior as apex of canine.

  • Palpation & Landmarking

    • Palpate mucobuccal fold depth from 1st molar → canine until depression (mental foramen) felt on lateral mandible.
    • Depression surrounded by smooth bone; patient often reports soreness on pressure (nerve proximity).

  • Target Area

    • Incisive nerve within mental foramen (Fig 9.50).

  • Injection Site & Technique

    • Site: Anterior to mental foramen, depth of mandibular mucobuccal fold.
    • Needle kept horizontal; syringe rests on lower lip (Fig 9.49).
    • Needle advanced without touching bone (cannot physically enter foramen in horizontal technique).
    • Deposition volume: greater than mental block.
    • Post-injection: Firm finger pressure over site → forces anesthetic into foramen, reaching mental → incisive nerves.
    • Sequence of onset: Soft-tissue (mental) → deeper pulpal (incisive).

  • Clinical Success Indicators

    • Tingling/numbness of lower lip + chin.
    • Pulpal anesthesia of indicated teeth.
    • No discomfort during invasive treatment.

  • Complications/Risks

    • High positive aspiration risk (close to incisive vessels).
    • Hematoma rare.

Mental Block (MB)

  • Essentially identical palpation, site, technique (Fig 9.48-9.49) but
    • Lower volume, no finger pressure.
    • Produces soft-tissue anesthesia only (no pulpal).
  • Same high aspiration risk, rare hematoma.

Gow-Gates Mandibular Block (G-G)

  • Scope & Nerves Anesthetized

    • Inferior Alveolar, Lingual, Mental, Incisive, Mylohyoid, Auriculotemporal, and (Long) Buccal ≈75%\approx 75\% of time.
    • Considered “true” mandibular block → entire third division (V3).
    • Clinical coverage (single quadrant):
    • ALL mandibular teeth + pulps to midline.
    • Lingual periodontium/gingiva for all.
    • Facial periodontium/gingiva of anteriors & premolars; usually buccal for molars.
    • Same extra-oral tissues as IA block.

  • Indications

    • Quadrant dentistry.
    • Failed IA blocks (accessory innervation, anatomic variation).
    • Desire for broader, more reliable anesthesia.

  • Advantages

    • Higher clinical success vs IA (mylohyoid nerve included).
    • Longer duration (less vascular area + larger volume).
    • Lower positive aspiration & hematoma risk (vessels further away).

  • Disadvantages / Contra-indications

    • Numbness of lip, temporal & buccal skin (patient dislike).
    • Slower onset (larger nerve trunk, 5!–!10 mm5!\text{–}!10\,\text{mm} away).
    • Mouth must stay widely open → not for limited opening (use V-A block instead).
    • Children / special-needs: prolonged numbness undesirable.

  • Target Area (Fig 9.52)

    • Anteromedial border of mandibular condyle neck, just inferior to lateral pterygoid insertion.

  • Extra-oral Landmarks (Fig 9.53)

    • Ipsilateral intertragic notch ↔ contralateral labial commissure line → parallels needle path.

  • Intra-oral Injection Site & Height (Fig 9.54-9.56)

    • Buccal mucosa on medial ramus surface, distal to mesiobuccal cusp of maxillary 2nd molar (or 3rd if present).
    • Height: just inferior to mesiolingual cusp of max 2nd molar.
    • More lateral than IA (edge of pterygotemporal depression), superior to occlusal plane by 10!–!25 mm10!\text{–}!25\,\text{mm} (patient-size dependent).
    • Needle advanced along path until bone (condylar neck) contacted.
    • Mouth held wide open throughout → condyle rotates forward, nerve trunk closer, tissues thinner (use bite block).

  • Troubleshooting Highlights (p. 196)

    • Tragus orientation affects syringe barrel position:
    • Flatter tragus → position syringe more anterior (closer to contralateral canine).
    • Tragus at 90∘90^{\circ} → syringe barrel more posterior (closer to contralateral 2nd premolar).
    • If bone not contacted:
    • May need deeper insertion in large/flaring ramus.
    • Or needle deflected mesially → withdraw, move barrel posterior (near contralateral 2nd molar) and re-insert.

  • Clinical Success Indicators

    • Numbness: mandibular teeth, facial + lingual periodontium/gingiva, ant. 2/3 tongue, floor of mouth, skin over zygoma/posterior buccal/temporal regions.
    • If buccal molar tissues inadequately numb → separate buccal block (buccal nerve ≈23 mm\approx 23\,\text{mm} from condylar site, concentration drops).

Vazirani-Akinosi Mandibular Block (V-A)

  • Scope & Nerves Anesthetized (similar to IA, but with mylohyoid & ~75% buccal)

    • IAN, Lingual, Mental, Incisive, Mylohyoid, ±(Long) Buccal.
    • NOT entire V3 → not a “true” block like G-G.
    • Anesthetizes:
    • Mandibular teeth to midline.
    • Lingual + facial periodontium/gingiva of anteriors & premolars.
    • Usually buccal periodontium/gingiva of molars.
    • Same extra-oral tissues as IA.

  • Key Feature: Closed-Mouth Technique

    • Ideal for patients with trismus (infection, trauma, post-injection) or limited opening.
    • Helpful when tongue/buccal fat pad obscure IA landmarks or for edentulous implant surgery.
    • Also for fearful patients refusing to open; alternative after IA failure (accessory innervation).
    • Contra-indicated with acute infection/inflammation within pterygomandibular space or maxillary tuberosity.

  • Target Area (Fig 9.58)

    • Medial surface of mandibular ramus inside pterygomandibular space, midway between mandibular foramen & condylar neck, adjacent to maxillary tuberosity.

  • Patient & Landmark Preparation

    • Patient gently occludes posterior teeth; masticatory muscles relaxed.
    • Clenching obliterates pterygomandibular space.
    • Retract cheek + buccal fat pad with instrument for visibility.
    • Intra-oral landmarks: medial ramus surface, maxillary tuberosity, mucogingival junction of max 3rd/2nd molar.

  • Injection Site & Path (Fig 9.59-9.61)

    • Buccal mucosa between medial ramus & maxillary tuberosity.
    • Needle parallel to maxillary occlusal plane.
    • Height = level of mucogingival junction of opposing max 3rd/2nd molar.
    • Needle passes medial to coronoid process (avoid temporalis insertion) then posteriorly/slightly laterally; hub ends opposite mesial surface of max 2nd molar.
    • No bone contact; deposit into center of pterygomandibular space.

  • Clinical Success Indicators

    • Same distribution as IA; rapid motor block → trismus relief enables wider opening.
    • Persistent trismus later → re-administer V-A; residual pain → supplement with LA, G-G, or supraperiosteal as needed.

  • Complications/Risks

    • Lower positive aspiration & hematoma risk vs IA (vessels further away) and less traumatic than G-G (mouth closed).
    • Over-insertion into parotid gland → transient facial nerve paralysis (same IA concern) (Fig 9.62).

Comparative Highlights & Misc. Numerical Facts

  • Volumes/Distances
    • G-G needle-to-nerve trunk distance ≈5!–!10 mm\approx 5!\text{–}!10\,\text{mm}.
    • G-G injection height above mandibular occlusal plane ≈10!–!25 mm\approx 10!\text{–}!25\,\text{mm}.
    • Buccal nerve ≈23 mm\approx 23\,\text{mm} from G-G deposition → may require extra buccal block.
  • Success/Failure Factors
    • Accessory innervation via mylohyoid nerve often causes IA failures; G-G & V-A routinely block mylohyoid, improving outcomes.
  • Aspiration Risks (highest → lowest): IA ≈ Mental/Incisive > G-G > V-A.
  • Hematoma frequency: Rare for all cited injections but risk correlates with aspiration probability.

Ethical & Practical Considerations

  • Patient comfort: Choose block minimizing unwanted numbness duration (e.g., avoid G-G in children).
  • Limited opening / trismus: V-A preferred; use as diagnostic & therapeutic (motor block relieves muscle spasm).
  • Anatomy-guided approach: Radiographs to locate mental foramen; palpation feedback; adjust for tragus orientation or ramus flare.
  • Avoiding tissue trauma: Keep needle clear of temporalis insertion (painful), parotid gland (facial palsy), vessels (hematoma).
  • Comprehensive quadrant anesthesia often needs supplemental buccal block even after broad mandibular blocks.