Systemic complications of local anesthesia

Complications of incisive anesthesia

Specific complications may arise during anesthesia in the incisive foramen region. Inserting the needle into the intraoral incisive canal is not always possible (e.g., in mandibular macrognathia or maxillary micrognathia), which is why the intranasal method (injection or topical application) is sometimes used.

Main complications:

• Epistaxis (nosebleed): occurs if, during the intraoral approach, the needle is advanced deeper than 1 cm into the incisive canal, leading to perforation and trauma of the nasal mucosa.
• Ischemia: the appearance of pale areas (ischemia) on the skin of the anterolateral face within the anesthetic's zone of action.
• Toxic reaction: characteristic of the topical application method if a swab soaked in a 1-2% tetracaine (amethocaine) solution with epinephrine is left in the inferior nasal meatus for too long.

Difficulties in mandibular anesthesia

The term "mandibular anesthesia" has historically become established, although anatomically it is not the mandibular nerve (n. mandibularis) itself that is blocked, but its branches: the inferior alveolar and lingual nerves. The goal of the injection is to deliver the solution to the mandibular foramen, which is covered by the lingula (lingula mandibulae).

Needle insertion problems: The mandibular ramus is angled relative to the sagittal plane, and the severity of this inclination varies individually.

• If, after advancing 0.75 cm and blocking the lingual nerve, it is impossible to advance the needle a further 2 cm due to a lack of bone contact, it means the needle is running parallel to the inner surface of the ramus.
• Solution: It is necessary to retract the syringe barrel further in the opposite direction—to the level of the second molar. This will alter the angle and allow the needle to reach the bony groove.

Anatomical factors of incomplete anesthesia

Lack of proper effect during a block is often associated with the patient's atypical anatomy. When performing an injection, especially using the apodactyl method (using the pterygomandibular raphe — plica pterygomandibularis as a landmark), one must consider:

1. Bifurcation of the inferior alveolar nerve.
2. Early branching of the posterior superior alveolar branch (before the main trunk enters the mandibular canal, canalis mandibulae).
3. Atypical topography of the mandibular foramen (in children and the elderly, it is located lower than the standard level).
4. Variations in structure or complete absence of the lingula.
5. The width of the raphe itself (with a wide raphe, the injection is made in its middle; with a narrow raphe, in its medial edge).

Prevention of complications through access modification

To reduce the risk of complications and improve injection accuracy, alternative techniques have been developed.

• P.M. Egorov's method: The anesthetic is injected into the interfascial pterygomandibular space. The advantage of this method is that at this level, the nerve has not yet merged with the corresponding artery and vein. This serves as reliable prevention against hematoma development and reduces the risk of intravascular injection.
• S.A. Rabinovich's method: The needle is directed toward the posterior edge of the tragus to a depth of 25 mm, targeting the lateral aspect of the mandibular neck. The anesthetic depot blocks three nerves simultaneously, and complications occur extremely rarely due to the distance of the zone from major vascular bundles (an aspiration test is mandatory!).
• Torus anesthesia (Vaisblat's method): The target point is the mandibular torus (torus mandibularis). It allows blocking the inferior alveolar, lingual, and buccal nerves simultaneously, reducing the number of required injections.

Extraoral approaches for trismus (jaw closure)

Limited mouth opening (trismus) is a condition that itself requires a change in tactics, as the intraoral approach is impossible.

Alternative extraoral routes:

• Subzygomatic approach (Berше-Dubov): injection perpendicular to the skin beneath the zygomatic arch to a depth of 3–3.5 cm. The solution is delivered between the heads of the lateral pterygoid muscle.
• From the submandibular region: the needle is advanced 3.5–4 cm along the inner surface of the ramus. A mandatory condition to prevent soft tissue trauma is to maintain constant sliding contact of the needle with the bone.
• Egorov-Lapis block: a two-stage injection through the soft tissues of the cheek. First, the buccal nerve is blocked, and then the needle is advanced to the mandibular foramen to anesthetize the alveolar and lingual nerves.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Anatomical landmarks for intraoral mandibular anesthesia with palpation
• Features of performing Vaisblat's torus anesthesia
• Positioning specifics for the Gow-Gates nerve block
• Topography of the pterygomandibular raphe in the apodactyl method
• Innervation zones of the nasopalatine nerve and rationale for the intranasal method

Other topics in "Chapter 12. Dental Anesthesia"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.