TOPOGRAPHIC STUDIES ASSOCIATED WITH INTRAORAL INJECTIONS [III] – MANDIBULAR LOCAL ANESTHESIA

04/04/2013 · by Perio Hung · in Oral Surgery. ·

  Mandibular bone (mandible) is considered as the strongest and largest bone, also, the last growth of the craninofacial structure. It is composed of 2 pieces of thick cortical bone, a lingual plate and a buccal plate with associated nerves, Inferior alveolar nerve, lingual nerves and buccal nerves. Depending on different procedures/ treatment, the technique should be elected for the suitable status. In general, mandibular anesthesia is more difficult to achieve comparing to the maxillary anesthesia due to the thickness of the cortical bone.

  Inferior alveolar nerve block is a common and useful technique. All mandibular teeth supported by inferior alveolar nerve, the epithelium of the anterior ⅔rds of the tongue, from the lingual nerve and the gingiva/ mucosa are anesthetized. Mostly all the treatment in situ of the mandible should perform this block. Of course, the short-term procedures such as basic extraction and scaling/ root planing (Sc/ Rp) are not necessary. Following with the steps to approach written in Netter’s Head and Neck Anatomy for Dentistry 2nd, Elsevier.

1.   Insert the needle into the mucosa between the deepest portion of the coronoid notch (which should represent the vertical height of the mandibular foramen) and just lateral to the pterygomandibular raphe.
2.   Orient the needle from the contralateral premolars and advance it along the occlusal plane of the mandible.
3.   The needle contacts the mandible after entering 20 to 25mm. (if bone is contacted immediately on penetration into the mucosa, then the temporal crest has been contacted; the needle should be reoriented to allow insertion to the proper depth)
4.   Withdraw the needle slightly and perform aspiration to determine whether the needle is in a blood vessel. (inferior alveolar vessels)
5.   After a negative result on aspiration (no blood observed in the syringe), slowly inject the anesthetic into the pterygomandibular space.
6.   If the result of aspiration is positive, readjust the needle position and perform aspiration again before injecting into the pterygomandibular space.

  It is important to pay a high attention when performing the techniques to the malocclusion patients. (Class II/ III)

  In class II malocclusion, when the mandible is hypoplastic, the mandibular foramen is typically located more inferior than the clinician may think.

  In class III malocclusion, when the mandible is hyperplastic, the mandibular foramen is typically located more superior than the clinician may think.

  Long buccal nerve block is a specific located block which situated a branch of the mandibular division of the trigeminal nerve, the long buccal nerve is not anesthetized in an inferior alveolar injection. Hematoma is rare with this block, and the injection seldom fails. It is dedicated for posterior teeth extraction, wisdom teeth extraction and posterior implants.

  Mental nerve block, a branch of the inferior alveolar nerve within the mandibular canal. The anesthetized area are all buccal gingiva and mucosa from premolars to the midline. And the skin part of the lower lip. By using radiographs images to locate the mental foramen for a better results.

There are another 2 techniques of mandibular local anesthesia.

  Gow-gates block, a variation of the inferior alveolar nerve block. The anesthetized nerves include inferior nerve, mylohyoid nerve, lingual nerve, long buccal nerve, auriculotemporal nerve. Low positive aspiration rate relative to that for the standard inferior alveolar nerve block injection. When the injection is properly administered, the needle contacts the neck of the mandibular condyle. All the mandibular teeth are anesthetized, also the buccal/ lingual gingiva/ mucosa. It is useful for multiple procedures on mandibular teeth and buccal soft tissue, however, with some complications which should proceed with caution.

  Akinosi block is a closed mouth approach for the mandibular nerve block. It anesthetizes inferior alveolar nerves/ branches, mylohyoid nerve, and lingual nerve. It is useful for mandibular depression (opened) is limited, such as with trismus. (suitable when the patient can’t open his mouth properly for Gow-gates block) Considered  a “blind injection.” The areas anesthetized are similar to Gow-gates block as well. The most different for the patient will be closing their mouth when proceeding. To the clinicians, the needle is is advanced approximately 23 to 25mm, it should be located in the middle of the pterygomandibular space near the inferior alveolar and lingual nerves, and there is no bone contact during the anesthesia.

Reference:

[1] Neil S. Norton, Netter’s Head and Neck Anatomy for Dentistry 1st, 2nd Edition, Saunders Elsevier.