Approaches for mandibular anesthesia
To reach the target area at the mandibular foramen, various approaches are used in clinical practice. The choice of method depends on the patient's anatomical features and the clinical situation.
The main methods for performing a mandibular block include:
- Intraoral approach. Performed from within the oral cavity. It can be carried out in two ways: palpatory (with mandatory palpation of anatomical landmarks with a finger) or apodictic (without palpation, relying on visual landmarks).
- Extraoral approach. Performed through the facial skin when the intraoral route is impossible or difficult.
Intraoral palpation technique algorithm
The palpatory method requires a clear understanding of the topographic anatomy of the mandibular ramus and correct positioning of the practitioner's hands. The success of the procedure directly depends on following the sequence of actions.
Preparation and landmark identification:
- The patient should open their mouth as wide as possible to provide the practitioner with full access and soft tissue tension.
- The practitioner inserts the index finger into the patient's retromolar fossa.
- In this area, it is necessary to clearly palpate the inner edge of the mandibular ramus — this is the main landmark for the subsequent injection.
Syringe positioning and injection site:
- The syringe is initially positioned at the corner of the mouth from the opposite side of the mandible, strictly at the level of the second premolar.
- The needle insertion point is located 1 cm posterior to the nail phalanx of the practitioner's index finger, which fixes the retromolar fossa.
- In terms of height, the insertion is performed 1 cm above the chewing surfaces of the large molars (lower molars). The needle is inserted perpendicularly until it contacts bone tissue.
Needle advancement and injection technique
The local anesthetic is administered in stages as the needle advances deeper into the tissues. This allows for the sequential blocking of the required nerve trunks.
Stages of drug administration:
- Lingual nerve block. When the needle is inserted to a depth of 0.75–1.5 cm, the practitioner releases the first small portion of the drug — about 0.2 ml.
- Bone contact. At a depth of 1.5–2 cm, the tip of the needle reaches the bone surface, where the next portion of the solution is injected.
- Vector change. The syringe is moved toward the anterior group of teeth (incisors), after which the needle is advanced further, sliding directly along the bone. The total insertion depth at this stage reaches 2.0–2.5 cm.
- Main injection. Before administering the main volume of the drug, an aspiration test is mandatory to rule out needle entry into a blood vessel. Only if the test is negative, the remaining anesthetic is injected in a volume of up to 1.8 ml.
Assessment of anesthesia efficacy
The effect of the drug during mandibular anesthesia does not develop instantaneously, so the practitioner must be able to assess objective and subjective signs of the blockade onset.
Characteristics of action:
- Onset time: when using modern local anesthetic solutions, deep anesthesia develops 5–10 minutes after injection.
- Duration: the effect lasts up to 1.5 hours. The exact time depends on the type of selected solution and the concentration of the vasoconstrictor added to it.
- Patient's subjective sensations: the first sign of a successful block is a change in sensitivity on the corresponding half of the lower lip. Patients describe this as a feeling of pronounced numbness, the appearance of local cold, tingling, or crawling sensations.
Briefly: answers to topical questions
Which anatomical regions and teeth are innervated by the inferior alveolar nerve?
- Mandibular teeth — all teeth of the corresponding half of the mandible.
- Alveolar process — the alveolar process and partially the body of the mandible.
- Mucous membrane — the mucous membrane on the buccal and labial sides from the last tooth to the midline, as well as the mucous membrane of the lower lip.
- Skin — the skin of the chin on the side of the anesthesia.
The inferior alveolar nerve is the largest branch of the mandibular nerve. Its intraosseous continuation after the mental foramen provides innervation to the incisors and canine.
What are the visual anatomical landmarks for performing the apodictic method of mandibular anesthesia?
- Pterygomandibular raphe (plica pterigomandibularis) — the main landmark located medial to the temporal crest.
- Outer slope of the pterygomandibular raphe — the specific injection site at the border of the upper and middle thirds of its length.
- Relation to teeth — the vertical injection level is located 1 cm above the chewing surface of the lower molars or in the middle of the distance between the chewing surfaces of the upper and lower molars.
The landmark is the pterygomandibular raphe without preliminary palpation of bone tissues.
What is the technique for performing the extraoral method of mandibular anesthesia?
- Injection site — the region of the base of the mandible, 1.5 cm anterior to the angle of the mandible.
- Needle direction — the needle is advanced upward along the inner surface of the ramus parallel to its posterior border.
- Mandatory condition — maintain constant contact of the needle with the bone throughout the entire advancement.
- Advancement depth — the needle is advanced 3.5–4 cm to block the inferior alveolar nerve and another 1 cm to turn off the lingual nerve.
- Dosage — 2 ml of anesthetic is injected.
What complications can occur during mandibular anesthesia?
- Muscular complications — numbness of the pharyngeal tissues and damage to the medial pterygoid muscle, leading to the development of mandibular contracture.
- Vascular complications — damage to blood vessels, hematoma formation, intravascular drug administration, and the appearance of skin ischemia zones.
- Neurological complications — neuritis upon mechanical damage to the lingual and inferior alveolar nerves, as well as facial muscle paresis due to blockade of facial nerve branches.
- Mechanical complications — fracture of the injection needle during a sudden change in its direction.
How does mandibular anesthesia differ from Weisbrem's torusal anesthesia?
| Characteristic | Mandibular anesthesia | Weisbrem's torusal anesthesia |
|---|---|---|
| Target point | Mandibular foramen (foramen mandibulae) | Mandibular torus (torus mandibulae) |
| Blocked nerves | Inferior alveolar and lingual nerves | Inferior alveolar, lingual, and buccal nerves |
| Injection site | Above the occlusal surface of the molars near the temporal crest | Intersection of the horizontal and vertical lines on the fold |
| Technique | Deep needle advancement with relocation of the syringe toward the incisors | The needle is advanced until bone contact at a depth of 0.2 to 2 cm |
Injection site for the palpation method: "1 cm back, 1 cm up" (relative to the fingernail and the occlusal surface of the molars, respectively).
Class and exam questions
Why release part of the anesthetic before reaching the target point?
At a shallow depth (0.75–1.5 cm), the solution is injected specifically to block the lingual nerve, which is located more superficially than the inferior alveolar nerve.
What happens if you skip the aspiration test?
Aspiration test is mandatory. Omitting it carries a high risk of intravascular administration of the full volume (up to 1.8 mL) of the anesthetic, which can lead to systemic toxic reactions.
How will the patient know the anesthesia has taken effect?
The main subjective sign is the onset of numbness, tingling ("pins and needles"), cold sensation, and prickling on the corresponding half of the lower lip. This typically occurs within 5–10 minutes.
What else to study on this topic
- Apodactyl intraoral technique
- Extraoral techniques for inferior alveolar nerve block
- Selection of local anesthetic and vasoconstrictor concentration
- Potential complications in the absence of an aspiration test
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