Maxillary infiltration: basic principles
Unlike the mandible, the lateral surface of the alveolar process of the maxilla consists of thin, porous bone tissue. This allows solutions to easily penetrate to the tooth root apices. The injection is typically performed in the transitional fold of the oral vestibule, slightly superior to the root apex projections.
Important rule: one should not aim to inject the drug strictly under the periosteum (subperiosteally). This is accompanied by pronounced pain due to mechanical tissue detachment and carries a high risk of complications. The efficacy of modern anesthetics is sufficient for diffusion from the submucosal layer. An interesting anatomical feature is found in the canines: their long roots project close to the infraorbital foramen, so the solution injected here can penetrate the canal and block the anterior superior alveolar nerves.
Locating the infraorbital foramen
The success of infraorbital anesthesia depends on the precise localization of the infraorbital foramen (foramen infraorbitale). Several landmarks are used to locate it:
- Relative to the orbital margin: 5–8 mm below the lower orbital rim.
- Relative to the dentition: on the line of the longitudinal axis of the second upper premolar.
- Palpatory landmark: a small depression located directly beneath the junction of the zygomatic process of the maxilla and the zygomatic bone (zygomaticomaxillary suture).
- Vertical line: the foramen lies on a straight line passing through the pupil of a patient looking straight ahead, the supraorbital notch, the corner of the mouth, and the mental foramen.
Infraorbital anesthesia: intraoral approach
In the intraoral method, the needle insertion is made in the transitional fold above the incisors. The needle is directed strictly toward the infraorbital foramen at an angle to the axis of the incisors and slides along the anterior surface of the jaw. 1 ml of anesthetic is injected.
Common mistake: if the needle is advanced from bottom to top strictly along the axis of the canine or premolars, its tip will hit the curvature of the canine fossa (fossa canina) and will not reach the target foramen.
Manual control: during solution injection, the practitioner must press with the finger of their free hand on the skin over the projection of the foramen. This directs the fluid flow deep into the infraorbital canal. Pressure must be maintained for another 1–2 minutes after carefully withdrawing the needle.
Infraorbital anesthesia: extraoral method
Having determined the projection of the foramen on the skin, the practitioner fixes the tissues with the index finger of the left hand (to prevent accidental injury to the eyeball). The insertion is made 1 cm lower and medially. The needle is advanced upward, posteriorly, and laterally until it contacts bone.
0.5–1 ml of solution is released in the region of the foramen. When using modern articaine-containing drugs, depot formation at the entrance is sufficient for an effective block of the anterior and middle alveolar branches.
Anesthesia zone: incisors, canine, premolars, and part of the medial buccal root of the first molar, as well as adjacent tissues on the vestibular side. On the face, the lower eyelid, lateral surface of the nose, and upper lip become numb.
Palatal anesthesia (greater palatine nerve block)
For full surgical intervention on maxillary teeth, vestibular block alone is not enough—tissues on the palatal side must also be anaesthetized. Palatal anesthesia turns off the nerves innervating the hard palate mucosa from the third molar to the canine.
The greater palatine foramen is usually located between the second and third molars. Insertion is made 10 mm anteriorly and medially from its projection. The needle is advanced upward, posteriorly, and laterally until bone is reached. A minimal volume is injected — 0.3–0.5 ml (after a mandatory aspiration test).
Complications of maxillary anesthesia
Interventions in the infraorbital and palatal areas are associated with certain risks:
- Soft palate paresis: occurs if the solution is injected too close to the greater palatine foramen or in excess volume. The patient experiences a foreign body sensation, nausea, and gagging due to the blockade of palatal muscles.
- Mucosal necrosis: the tightly bound tissue of the hard palate does not tolerate rapid injection under pressure. This causes reflex vascular spasm, ischemia, and tissue necrosis (especially in elderly patients with atherosclerosis).
- Infraorbital region complications: if technique is violated, double vision (diplopia), infraorbital neuritis, hematoma formation, or areas of ischemia (blanching) on facial skin may occur.
Briefly: answers to topical questions
Which nerves are blocked during infraorbital anesthesia?
During infraorbital anesthesia, the peripheral branches of the infraorbital nerve and the superior alveolar nerves are blocked. These include:
- Peripheral branches of the infraorbital nerve — form the "minor goose's foot" (pes anserinus minor).
- Anterior superior alveolar nerves (rr. alveolares superiores anteriores) — innervate the incisors and tissues of the anterior maxilla.
- Middle superior alveolar nerves (rr. alveolares superiores medii) — together with other branches form the superior dental plexus.
Which innervation zone is turned off during incisive anesthesia?
During incisive anesthesia, the innervation zone of the nasopalatine nerve is turned off, including the mucous membrane and periosteum of the alveolar process on the palatal side and the hard palate. This area has a triangular shape:
- Apex — directed toward the median palatine suture.
- Base — directed toward the anterior teeth.
- Sides — pass through the middle of the canines.
The borders of the zone are variable: it can narrow exclusively to the area of the central incisors or expand up to the first premolar inclusive.
Which target nerves are blocked during palatal anesthesia?
During palatal anesthesia, the target is the greater palatine nerve (n. palatinus major), passing through the greater palatine foramen. With the administration of a large volume of anesthetic, needle penetration into the canal, or injection posterior to the greater palatine foramen, blockade of soft palate nerve trunks, including the lesser palatine nerves (nn. palatini minores), is possible.
Class and exam questions
Why does the needle often fall short of the target during an infraorbital block?
This happens if the practitioner advances the needle strictly along the axis of the canine or premolars. In this case, the tip rests against the anatomical depression — the canine fossa (fossa canina).
Why press a finger on the skin during an infraorbital injection?
Digital pressure prevents the distribution of the anesthetic in the soft tissues of the face and directs the fluid flow strictly inside the infraorbital canal. Pressure should be applied during the injection and for 1–2 minutes after it.
Is it permissible to inject a standard volume (1–2 ml) of anesthetic under the palate?
Categorically no. Due to the tight adhesion of the mucosa to the periosteum, administering a large volume will cause blood vessel compression and lead to tissue necrosis. The optimal dose for palatal anesthesia is 0.3–0.5 ml.
What else to study on this topic
- Anatomical and topographical data of the nasopalatine nerve
- Incisive anesthesia: technique and coverage areas
- Tuberosity anesthesia according to P.M. Egorov's method
- Complications involving the pterygoid venous plexus
- Hydrodissection of tissues during conduction anesthesia
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