Symptoms of anaesthesia - Mandibular teeth on one side become numb (via inferior alveolar nerve block) - Lower lip and chin on one side become numb (via mental nerve block) - Parts of the tongue and lingual gingival tissue on one side, except for the cheek side of the mandibular molars, become numb (via lingual nerve block) - Tongue and floor of the mouth may experience harmless numbness and tingling (indicating lingual nerve anaesthesia) - Lingual shock may occur as the needle passes by the lingual nerve during administration

Injection techniques - Inferior alveolar nerve block (IANB) is commonly used, approaching the nerve from the opposite side of the mouth over the contralateral premolars - Gow-Gates technique involves directing the needle at the neck of the condyle just under the insertion of the lateral pterygoid muscle - Vazirani-Akinosi technique is a closed-mouth injection technique, advancing the syringe parallel to the maxillary occlusal plane at the level of the maxillary mucogingival junction - These techniques are used for extensive anaesthesia or when the patient cannot open their mouth enough for the IANB

Complications - Accidental self-inflicted trauma may occur after the procedure, such as biting the lip or tongue or thermal burn from drinking hot fluid - Puncturing a blood vessel accidentally may cause a hematoma or blood blister that will heal over time - Injection positioned too posteriorly may put anesthetic into the parotid gland, causing temporary facial paralysis - Injection placed too medially may result in injection of the medial pterygoid muscle, leading to trismus - Shallow injection may result in the sphenomandibular ligament acting as a barrier to the anesthetic, affecting only the lingual nerve

Additional information - The inferior alveolar nerve block aims to anesthetize the inferior alveolar nerve before it enters the mandibular foramen on the medial surface of the mandibular ramus - The long buccal nerve may not be anesthetised by an IANB, requiring a separate buccal nerve block for anaesthesia of the buccal gingiva adjacent to the lower posterior teeth - Lingual shock is a momentary symptom that may occur as the needle passes by the lingual nerve, causing an involuntary movement in the patient - Needle tract infections of the pterygomandibular space can rarely occur due to inoculation of bacteria from the mouth during the injection - The procedure can cause temporary numbness and tingling in the body of the tongue and floor of the mouth, indicating anaesthesia of the lingual nerve

References - Agur, Anne M.R., and Arthur F. Dalley. Grants Atlas Of Anatomy. 12th ed. Maryland, USA: Lippincott Williams & Wilkins, 2009. - Aker, F. D. (2001). Blocking the buccal nerve using two methods of inferior alveolar block injection. Clinical Anatomy. 14 (2): 111–119. - Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 216 - Meechan JG (January 1999). How to overcome failed local anaesthesia. Br Dent J. 186 (1): 15–20. - Local Anaesthesia for the Dental Hygienist, Logothetis, Elsevier, 2012