Anatomical anesthesia zones
When the block of the mandibular and lingual nerves is performed correctly, loss of sensitivity occurs in strictly defined anatomical regions.
Main structures that lose pain sensitivity:
- All teeth on the side of the injection.
- Bone tissue of the alveolar process and partially half of the mandibular body.
- Mucous membrane on the labial and vestibular sides, extending from the most distal tooth all the way to the midline of the jaw.
Crucial condition for total anesthesia: Even with flawless technique, the anterior region of the mandible may retain residual sensitivity. This is due to nerve anastomoses coming from the opposite side of the jaw. To completely block these branches and achieve absolute patient comfort, an additional anesthetic solution must be administered along the mucobuccal fold directly in the anterior region.
Signs of successful block and associated effects
The correctness of the solution delivery can be assessed by characteristic subjective patient sensations indicating the involvement of the lingual nerve.
Key symptoms typically develop within 3–5 minutes and include:
- A feeling of pronounced numbness in the corresponding half of the tongue.
- Specific tingling localized in the area of the tongue tip.
The clinical value of these signs is that they serve as a reliable indirect confirmation that the solution has reached the target and that the inferior alveolar nerve has also been successfully blocked.
Additionally, a concomitant effect is often observed during the procedure — unintended blockade of the buccal nerve. This leads to supplementary anesthesia of the oral mucosa on the outer aspect of the alveolar process from the second premolar to the second molar.
Complications associated with inaccurate administration
Deviation from correct anatomical landmarks can lead to a number of adverse consequences.
If the needle is mistakenly inserted medial to the pterygomandibular raphe, the anesthetic spreads into unintended fascial spaces. As a result, the patient may complain of numbness in the pharyngeal tissues. Moreover, such a trajectory carries a high risk of injuring the medial pterygoid muscle, which subsequently predictably leads to inflammation and mandibular contracture (limited mouth opening).
Infectious and inflammatory complications are also possible. A breach of asepsis rules or infection of a hematoma can provoke post-injection inflammatory processes directly in the pterygomandibular space.
Vascular and neurological risks
A dense neurovascular bundle runs through the manipulation area, damage to which causes specific complications.
Vascular complications:
- Mechanical damage to blood vessels by the needle tip causes local hemorrhage and hematoma formation.
- Accidental intravascular administration of the anesthetic (requires aspiration testing).
- Vascular spasm or the action of a vasoconstrictor can cause sharply demarcated zones of ischemia (blanching) on the skin of the chin and lower lip.
Neurological complications:
- Direct mechanical trauma to the trunks of the inferior alveolar or lingual nerves by the injection needle. This traumatic impact often triggers the development of neuritis.
- Occasionally, the anesthetic solution may diffuse too deeply, causing a temporary block of facial nerve branches. Clinically, this manifests as paresis of the facial musculature on the affected side of the face.
Injection needle fracture
One of the most frightening complications in practice is the breakage of an injection needle deep within soft tissues. The typical and most vulnerable fracture site is the transition zone where the metal shaft meets the plastic hub.
Main causes of fracture:
- Sudden, uncontrolled changes in the direction of the needle's movement while it is already deeply embedded in soft tissues.
- The needle tip catching in a narrow space between bone and muscle, leading to bending stress.
- Accidental penetration of the tip into a dense muscle tendon (the tendon of the temporalis muscle is most frequently affected).
Preventive measures: To prevent instrument breakage, only high-certified dental carpule needles must be used. The clinician must strictly follow the manipulation technique, completely eliminating rough and abrupt movements. It is strictly prohibited to insert the needle into tissues to its full length all the way to the hub.
Management of a fractured needle: If the fragment has completely disappeared into the tissues, any attempts at its immediate search and retrieval in an outpatient dental setting are strictly prohibited. The patient must be urgently referred to a specialized maxillofacial inpatient facility, where surgical removal of the foreign body will be performed only after a thorough radiographic examination.
Briefly: answers to topical questions
What intraoral anatomical landmarks are used for needle insertion during mandibular anesthesia?
Mucosal folds, bony structures, and teeth are used as landmarks for needle insertion during intraoral mandibular anesthesia techniques.
- Pterygomandibular raphe (plica pterygomandibularis) — insertion is performed at its outer edge (at the border of the upper and middle thirds) or in the groove between its lateral slope and the cheek.
- Internal oblique line — insertion is carried out posterior to it.
- Lower molars — referenced 1 cm above their chewing surface.
- Upper molars — serve as a key landmark in P.M. Egorov's method and torus block anesthesia.
- Intermuscular triangle — taken into account in the topography according to P.M. Egorov's method.
Which anatomical structures bound the pterygomandibular space?
The pterygomandibular fascial space is bounded externally by the inner surface of the mandibular ramus and internally by the interpterygoid fascia covering the medial pterygoid muscle. The space is located superior to the mandibular foramen; dense borders prevent the spread of the solution and help concentrate it within this space.
Where is the mandibular foramen (foramen mandibulae) located anatomically?
Anatomically, the mandibular foramen (foramen mandibulae) is located at the midpoint of the mandibular ramus. It is situated directly beneath the pterygomandibular space. The effective axis of mandibular motion (around the condyle and articular tubercle) is projected onto this area, keeping the foramen region relatively immobile and reliably protecting the neurovascular bundle from trauma. The inferior alveolar nerve, along with the accompanying artery and vein, enter the mandibular canal through this foramen. To accurately determine its projection, the mandibular ramus is conventionally divided into four quadrants by intersecting vertical and horizontal lines.
Which nerves innervate the mucosa of the mandibular alveolar process from the vestibular side?
The mucosa of the mandibular alveolar process from the vestibular (outer) side is innervated by branches of the buccal and mental nerves.
- Buccal nerve (n. buccalis) — innervates the gingiva on the vestibular side in the premolar and molar region (from the second premolar to the second molar).
- Mental nerve — innervates the mucosal membrane on the vestibular side in the anterior region (within the area of the incisors, canines, and premolars).
For complete anesthesia of this zone during surgical interventions in the posterior teeth region, an additional mandatory block of the buccal nerve is required, while in the anterior region, blocking the anastomotic branches from the opposite side is necessary.
Class and exam questions
Why did the anterior teeth fail to achieve complete anesthesia?
This is due to the presence of nerve anastomoses (branches) from the opposite side of the jaw. For complete anesthesia of the anterior region, an additional local anesthetic must be injected along the mucobuccal fold in this area.
How quickly should the local anesthetic take effect?
Normally, initial signs such as numbness of half of the tongue and tingling of its tip appear 3–5 minutes after drug administration.
What to do if the needle breaks and completely penetrates the mucosa?
It is forbidden to try to retrieve it independently at the out-patient clinic. Immediate referral of the patient to a maxillofacial inpatient department is required for X-ray control and surgical removal.
What causes pharyngeal numbness during this technique?
Pharyngeal numbness is a sign of incorrect needle insertion too medially (internally) to the pterygomandibular fold, which also carries the risk of trauma to the medial pterygoid muscle.
What else to study on this topic
- Anatomy of the pterygomandibular space
- Prevention and treatment of lower jaw contracture following injection
- Aspiration test technique to prevent intravascular administration
- Clinical presentation and treatment of traumatic neuritis of the inferior alveolar nerve
- Supplementary anesthesia techniques for the anterior mandible
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Other topics in "Chapter 4. Anesthesia in Oral Surgery (S.A. Rabinovich, S.T. Sokhov)"
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