What Is a Posterior Superior Alveolar Nerve (PSAN) Block?
Local anesthesia has been practiced over the last few decades effectively in dentistry to address the most common fear of pain amongst dental patients to achieve effective pain control. The most common surgical procedure done by general dentists or even oral and maxillofacial surgeons is mainly the extraction of decayed teeth or teeth that need to be removed due to mobility or infections, which is carried out using local anesthesia. Anesthesia in the maxillary region or the upper jaw segment is mainly achieved by administering the local anesthetic solution through the commonly preferred infiltration block or procedure. The posterior superior alveolar nerve (PSAN) block is an efficacious nerve block used by most clinicians to achieve effective pain control during extraction of the maxillary molars, the maxillary second and third molars.
What Does the Posterior Superior Alveolar Nerve Block Anesthetize?
The PSAN is a major sensory branch of the maxillary division of the fifth cranial nerve or the trigeminal nerve. The PSAN block is used for anesthetizing the posterior maxillary teeth and the surrounding structures supplied by the posterior superior alveolar nerve. This technique, like any other anesthetic block in dentistry, is to deposit the solution close to the main nerve trunk before the solution permeates or enters into the bone or any deep tissue. The posterior superior alveolar nerve pathway or nerve course is through the posterior surface of the maxilla midway between the alveolar border and the orbital surface of the upper jaw or maxilla. This is the main target area for solution deposition through this nerve block.
What Are the Anatomical Landmarks of Posterior Superior Alveolar Nerve Block?
The anatomical landmarks include:
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Mucobuccal fold and the concavity of the mucobuccal fold in the maxillary posterior region to be anesthetized.
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The zygomatic process of the maxilla.
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The infratemporal surface of maxilla
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The anterior border of the mandible or lower jaw
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The coronoid process of the ramus of the mandible.
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The Maxillary Tuberosity region.
What Are the Indications of Posterior Superior Alveolar Nerve Block?
A posterior superior alveolar nerve block is mainly indicated in operative procedures that involve the extraction of maxillary molars. Other indications include:
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Failed root canal treatment in maxillary molars
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Extensive flap surgery procedures of the maxillary region
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Impactions of the maxillary third molar.
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Periodontally diseased molars with a poor prognosis like infection and mobility.
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Grossly decayed molars.
How Is Posterior Superior Alveolar Nerve Block Given?
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The clinician assembles the appropriate armamentarium and dries the injection site. The patient is asked to open their mouth.
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Tissue retraction facilitates injection for the dental surgeon to achieve adequate depth and angulation for this nerve block.
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Before the needle is oriented at the injection site, an extraoral fulcrum or support is established extraorally on the patient.
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The syringe barrel is oriented at a 45 degrees inclination (downward and lateral away from the midsagittal plane) at the height of the mucobuccal fold and distal to the zygomatic process of the maxilla. The 45 degrees of inclination is important as it needs to be angulated away from the occlusal plane of the upper jaw.
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Before needle advancement before deposition of the anesthetic solution, consecutive negative aspirations are recommended by most clinicians to avoid infection. The needle advanced upon the target site into the mucobuccal fold.
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The clinician or surgeon may deposit approximately around 0.8-1.8 ml of anesthetic solution ideally for 60 seconds.
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If the mesiobuccal root of maxillary first molars is not effectively anesthetized in some patients, the middle superior nerve block must also be given to control pain.
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The additional palatal injection must be administered in patients with furcations or root concavities or if the palatal roots are not effectively anesthetized only with PSAN block.
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The needle in the posterior superior alveolar nerve block extends into the oral mucosa.
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The needle extends through the areolar tissue, then passes through the buccal fat if present in the patient.
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The needle also eventually extends or pierces the buccinator muscle posterior fibers.
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The dental clinician should always be careful to avoid surgical complications like hematoma, and diplopia, which may be possible consequences when the blood vessels, tissue, artery, or veins are punctured or injured.
Why Is Post Superior Alveolar Nerve Block Preferred?
The straight needle technique is one of the most commonly used techniques. Case reports have showcased more than 95 % documented and successful anesthetic control in cases of upper molar extractions. According to Lawrence Pfeil et al ., this technique may achieve approximately 97 % success rate of anesthesia for second molars. In contrast, it is only around 77 % for first molars, which can be attributed to most patients' middle superior alveolar nerve. The anterior middle superior nerve (AMSA) block is also a preferred technique for effectively anesthetizing the premolars and first molar. The advantage of using a PSAN block in the case of third molar extraction is that effective palatal anesthesia is already achieved without the additional need to inject palatally by avoiding the palatal injection.
Conclusion
The PSAN block is used for anesthetizing the posterior maxillary teeth and the surrounding structures supplied by the posterior superior alveolar nerve. This technique is mainly indicated in operative procedures that involve the extraction of maxillary molars. The nerve block requires operator skill, tactility, and knowledge of anatomic landmarks and areas to be anesthetized.
