Posterior Superior Nerve Block is used to block or Anesthetize the Posterior Superior alveolar Nerve which will anesthetize the Maxillary Molars except the Mesio-Buccal root of First Maxillary Molar which is supplied by the Middle Superior Alveolar Nerve. Posterior Superior Nerve Block the LA agent is deposited in proximity to the
- Mucobuccal fold and its concavity
- Zygomatic process of the maxilla
- Infratemporal surface of maxilla
- Anterior border and coronoid process of the Ramus of the mandible
- Maxillary Tuberosity
Posterior Superior Alveolar Nerve and its branches
- The areas of the Oral cavity which are supplied by the Posterior Superior alveolar nerve are anesthetized
- Maxillary Molars of the Side of injection except the Mesio-Buccal Root of the Maxillary First molar
- Buccal alveolar process covering the maxillary molars
- Periosteum covering the Maxillary molars
- Connective tissue covering the Maxillary molars
- Mucous membrane covering the Maxillary molars
Indications of PSA Nerve Block:
- Posterior Superior alveolar nerve block is indicated in any operative procedure involving the Maxillary molars like
- Root canal treatment in maxillary molars (in case of Maxillary First molar PSA should be accompanied along with Infra Orbital nerve block to anesthetize the Mesio Buccal Root as well)
- Extraction of Maxillary Molars in case of 1st molar PSA + Infra Orbital is recommended
- Flap Surgery in the 1st and 2nd quadrants of Maxilla
- Impactions of Maxillary Third molar
Note: In case the palatal aspect of the Maxillary teeth are involved in the operative procedure PSA should be accompanied with Posterior Palatal Injection to get area completely anesthetized.
Needle Pathway during Insertion:
The needle in the Posterior Superior alveolar nerve block extends from the mucosa first and then pierces through the areolar tissue and some times passes through the Buccal fat in case it is present in the patient and lastly it pierces the posterior fibers of the Buccinator muscle.
Approximating Structures to the Needle:
- The structures which will be around the needle after it reaches its final position for deposition of Local anesthetic agent to anesthetize the Posterior Superior Alveolar Nerve are:
- The needle will not pierce the nerve but be in proximity to the Posterior Superior alveolar canal through which the posterior superior alveolar nerve, artery and vein pass.
- Needle is present Anterior and Lateral to the anterior margin of the external pterygoid muscle
- Posterior to the posterior surface of the maxilla
- Anterior to the pterygoid plexus of veins
Technique or How to give Posterior Superior Alveolar Nerve Block:
Patient Position for Posterior Superior Alveolar Nerve block:
The patients Head and Neck are kept in a straight line and the back rest of the dental chair is tilted to a 45 degree angle to the floor, this helps to keep the occlusal plane of the patient at 45 degrees when the patient opens his/her mouth.
Operator Position for Posterior Superior Alveolar Nerve Block:
the Operator or the dentist stands on the Right side of the patient and the clock positions are different fr the Right and Left sides as follows:
Right PSA nerve Block the operator stands at 8 o’clock position
Left PSA nerve Block the operator stands at 10 o’clock position
- Now coming to the Technique the operator places his/her left forefinger over the mucobuccal fold on the buccal aspect of Second Premolar and moved in posterior direction from this area until the finger contacts the zygomatic process of maxilla.
- Now the posterior surface of the left forefinger tip rests in the concavity in the mucobuccal fold.
- Now the finger is rotated such that the finger nail side is towards the tooth and the bulbous side towards the cheek or posterior surface of Zygomatic process. Ask the patient to close his/her mouth partially to relax the muscles.
- Lower the finger keeping the Bulbous portion still in contact with the zygomatic process so that the finger is in a plane at right angles to the patients sagittal plane. Now cheek portion should be pulled laterally and posteriorly while maintaining the position of the finger.
- This index finger should be taken as a guide to insert the 25-27 gauge long needle Injection in the same direction which is held in pen grasp to get the best result.
- The needle is inserted parallel to the finger and bisecting the Finger nail following the “upward, inward and backward direction” and extending to a depth of 1/2 to 3/4th of an inch.
- This will place the needle tip in vicinity of the Foramen through which the Posterior Superior Alveolar Nerve, Artery and Vein pass.
- The needle has to be aspirated while keeping the needle in position to make sure that the needle is not in some Artery or Vein which will draw blood into the needle on aspiration and the syringe/liquid cartridge should be discarded and a new syringe/cartridge should be used.
- Slowly inject the LA Agent into the space and the agent diffuses the tissues surrounding and will take 5 minutes to start its anesthetizing action. So any procedure which are to be performed should done after 5 minutes and after checking for Subjective and Objective Symptoms.
Objective Symptoms: Instrumentation should be done, use either the Tip of a blunt Probe or Elevator to check for Objective symptoms. The anesthetized tissue and teeth should be pressed and tapped as compared to the un-anesthetized side.
Subjective Symptoms: We cannot find any particular Subjective symptoms in any patients so objective symptoms tell us the effect.
Complications seen in Posterior Superior Alveolar Nerve Block and their treatment:
The Posterior Superior Alveolar nerve block is a very easy block but it is also the most common nerve block to get Hematoma Formation in case the PSA Vein or Artery is pierced due to their close proximity to the final needle tip position.
There is no need of any intervention as the hematoma subsides by itself after sometime and inform the patient that the swelling will subside over time, there will be not be any pain in most instances but in case there is any pain of increase in swelling and blood pooling should be addressed to immediately.