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Braz Dent J (1990) 1(1): 31-36 ISSN 0103-6440

| Introduction | Description of technique | Conclusions | References |

The superior lateral labial frenum is proposed as a new anatomic reference for the intraoral blocking technique of anesthesia of the anterior and middle superior alveolar nerves (infraorbital). The main advantage of this technique is the constancy of the reference point, independent of the presence or absence of teeth, which other techniques do not offer.

Key words: anesthesiology, infraorbital block.

Introduction

The anatomical location of this foramen has been studied by numerous authors. Martani and Stefani (1965), studying the position of this anatomic accident within statistical, morphological and topographical aspects, provide an extensive bibliographical review of this topic.

From a practical standpoint in anesthesiology, despite the fact that the infraorbital, foramen is found easily by digital palpation, or by other methods based on fines traced between craniometric points (Haglund and Evers, 1972; Bennett, 1977), the establishment of a. constant reference point for needle insertion is of great importance for successful intraoral injection.

The relevant literature shows a tendency of a majority of the authors to use the teeth as the reference for intraoral blocking techniques. Thus, Archer (1955) and Schram (1964) cite the maxillary central incisor, Partsch (1936) the maxillary lateral incisor, Maurel (1944) and Ries Centeno (19M) the maxillary canine, Mead (1948), Nevin and Puterbaugh (1955), Archer (1955) and Jorgensen and Hayden (1970) the maxillary second pre-molar, and Graziani (1958) and Bennett (1977) the maxillary pre-molars.

These references are, however, annulled when these teeth are absent, a fact frequently observed in dental practice. Thus, if there existed an anatomic accident always constant and present in everyone, which would ease the orientation of the needle in the direction of the infraorbital foramen during its introduction into the tissues, this anesthetic technique would be of great value for all patients, especially edentulous patients.

The objective of this study is to propose the superior lateral labial frenum as the new anatomical reference to be observed for the locafization of the needle insertion point in infraorbital intrabuccal blockage.

Description of technique

About 5-6 mm before the foramen, the infraorbital nerve supplies the anterior maxillary alveolar nerve whose branches descend by narrow canals in the maxilla, running between the sinus mucosa and the bony wall, penetrating through the radicular apices, to innervate the pulp of maxillary incisors and canines. Its branches also go to the outer bone plate, periosteum and other lining structures in the region of these teeth. It even gives sensibility to the mucosa of the anterior part of the maxillary sinus. A prolongation crosses the maxilla in direction of the floor and lateral wall of the anterior nasal cavity.

The middle superior alveolar nerve separates from the infraorbital nerve at the posterior part of the floor of the infraorbital canal and continues in a downward frontal direction until the pre-molar apices. At other times, it separates near the infraorbital foramen and descends by the anterior wall or the anterolateral maxillary sinus until the superior pre-molars, innervating the dental pulp, the external alveolar lamina, the periosteum and the mucosa. Several authors maintain that the middle superior alveolar nerve may be absent and that, in this case, the maxillary pre-molars are innervated by the external superior plexus.

Infraorbital block anesthetizes the anterior and middle maxillary alveolar nerves, inferior palpebral, lateral nasal and superior labial with insensibility of the maxillary incisors, canines and pre-molars, including their vestibular osseous support and the soft tissues which cover them, as well as the mesiovestibular root of the maxillary first molar, part of the maxillary sinus, nose, superior labial and inferior palpebral.

To execute this proposed technique, the patient ought to be seated comfortably, with the mouth open, reclining backwards, so that the maxillary occusal plane forms a 45° angle with the floor (Alonso Verri, 1964). The upper lip is raised, revealing the marina lateral labial frenum (Figure 1).

With a long needle (about 42 mm) mounted on a syringe resting on the lower lip, the needle is introduced vestibularly to the gingival sulcus, about 1 cm from the mucosa of the alveolar process, touching lateral and parallel to the superior labial frenum (Figure 2).

The needle ought to be oriented as if it would virtually encounter the base of the superior lateral labial frenum on the infraorbital border (Figure 3).

The penetration of the needle is stopped when the needle reaches the infraorbital foramen, the patient generally complaining of an electrical shock or burning. The anesthetic solution is injected slowly, maintaining a finger applied to the foramen so that the anesthetic solution is driven into the area of less resistance - the infraorbital canal - in this manner reaching the anterior and middle maxillary alveolar branches.

The success of this procedure is the lack of sensibility to thermal, painful and tactile stimuli in the region innervated by the anterior and middle maxillary alveolar branches and by the drooping of the upper lip on the anesthetized side, shoving that the terminal branch of the facial nerve (temporofacial) was reached in the infraorbital foramen region (Figure 4).

With the anesthetic solution reaching only the terminal branches of the infraorbital nerve (in the region of the foramen), purely subjective symptoms cannot be taken into consideration to evaluate the success of the anesthetic block.

Two muscles may be affected by incorrect execution of this technique: the canine muscle which fills the canine fossa, and the elevator muscle of the upper lip which inserts at the lower border of the orbit. The infraorbital foramen is between the insertion of these two muscles. If the needle is maintained near the bone, the canine muscle will be affected; but if it is too far from the bone, the proper elevator muscle of the upper lip will be affected.

One ought to avoid reaching the orbit so that the ocular-motor and optic nerve branches are not affected, the consequences being double vision and temporary blindness. These accidents, although transitory and rare, are extremely disagreeable. Rarely do intravascular injections occur.

In cases near the midline, a complementary infiltration of the opposite side is recommended so that eventual crossed nerve junctions are also anesthetized.

Conclusions

The anatomic reference point presented here is constant in all patients - with or without teeth.

The superior lateral labial frenum is a fold in the mucosa of the gingival sulcus, inserting in the region of the maxillary canines and pre-molars. It is generally not noted on superficial examination. To be evident, it is necessary to raise the buccal mucosa, separating it from the gingival mucosa causing its distension by the attempt of gingival sulcus planing.

The practical application, with complete success, of the anesthetic block of the infraorbital nerve by the above technique recommends the superior lateral labial frenum as the infraoral reference point in patients with or without teeth. Clinical experience in the application of this technique permits the proposal that the localization of the infraorbital foramen corresponds to the superior lateral labial frenum and that this correspondence is invariable and always present.

References

Archer WH: Anestesia en odontologia - Manual ilustrado. Ed Mundi, Buenos Aires 1955

Bennett CR: Monheim - Anestesia local e controle da dor na prática dentária. 5th ed. Guanabara-Koogan, Rio de Janeiro 1977

Graziani M: Cirurgia buco-maxilar. 4th ed. Vol I. Ed. Cientifica, Rio de Janeiro 1958

Haglund J, Evers H: Local anesthesia in dentistry. Astra Lakemeded AB, Malmoe 1972

Jorgensen NB, Hayden JR: Anestesia odontológica. Interamericana, México 1970

Martani F, Stefani F: Contributo statístico, morfológico e topográfico alto studio del fore infraorbitário in crani umani. Mondo Odontostomatol 7: 367-378, 1965

Maurel G: Cirugia maxilo-facial. Alla, Buenos Aires 1944

Mead SV: Cirugia bucal. 3rd ed. Vol I. UTEHA, México 1948

Nevin M, Puterbaugh PG: Anestesia dentária. 11th ed. Ed. Cientifica, Rio de Janeiro 1955

Partsch C: Enfermedades quirúrgicas de la boca, dientes y maxilares. 4th ed. Labor, Buenos Aires 1936

Ries Centeno GA: Cirugia bucal. 7th ed. El Atheneu, Buenos Aires 1964

Schram WNR: Técnicas de cirurgia oral. Ed. Cientifica, Rio de Janeiro 1964

Correspondence: Dr. José Inácio Saadi Salomão, Departamento de Cirurgia e Traumatologia Bucomaxilofacial, Faculdade de Odontologia de Ribeirão Preto, USP, 14050 Ribeirão Preto, SP, Brasil.