**2. Standard Inferior Alveolar Nerve Block (SIANB)**

There are many reasons why the success rate of SIANB is low. One is that the dentist can make mistakes during the technique. These problems are easily resolved by reviewing the anatom‐ ical landmarks and the steps to perform the technique involved. Another important reason is the presence of inflamed or infected tissue. Infection areas are acidic, which can influence the beginning of anesthesia. When infection occurs, it is necessary to administer an injection into a deeper location away from infection to avoid this problem. A third reason is that a patient's anxiety often can cause local anesthetic failure. [6] This problem can be solved by the discussion with his fear of injections patient and, if necessary, considering the use of minimal sedation such as that provided by nitrous oxide. Intravascular injection may be another reason for failure because the local anesthetic can be taken away from the site of action. This problem can be avoided by careful aspiration before any injection [7].

Anatomical variability and accessory innervation can also be a problem in providing successful mandibular anesthesia. Once the needle has penetrated the oral mucosa, the dentist is essentially proceeding in a blind mode and assuming that the patient has the same anatomy learned in the dental school. All patients anatomy, however, are not the same and this anatomic variability can lead to failure of SIANB. [8]

Accessory innervation occurs when the main inferior alveolar nerve trunk is not the only source of innervation to the pulp. This accessory innervation may arise from various sources such as a distinct branch from alveolar nerve [8], mylohyoid nerve, as well as the buccal, lingual or auriculotemporal nerves. This situation can be diagnosed when the patient has signs of a successful mandibular nerve block such as a dormant lip, but the tooth is still sensitive when stimulated with a drill [8,9].

Although some researchers report that the success rates for alternative blocks are higher than those reported for SIANB [8,10], others reported comparable rates [11,12]. However, research‐ ers of the latest study reported that the best rate for SIANB was probably due to the experience of dentists who administer the anesthetic blocks. [12]

The main objective of each block of the mandibular nerve is the inferior alveolar nerve anesthesia, which innervates the pulps of the lower teeth, as well as the buccal periodontium anterior to the mental foramen. This is achieved by depositing the anesthetic within pterygo‐ mandibular space. This anatomic space encloses the inferior alveolar nerve and the lingual nerve. The pterygomandibular space also contains the inferior alveolar artery and vein and sphenomandibular ligament. This space is limited laterally by the mandibular ramus, medially and inferiorly by the medial pterygoid muscle, superiorly by the lateral pterygoid muscle,pos‐ teriorly by the parotid gland and anteriorly by the buccinator muscle [10,11].

The Gow-Gates and Akinosi-Vazirani methods are indicated when there is anatomical variation or accessory innervation. The Akinosi-Vazirani method is also indicated when the patient has limited mouth opening or whose tongue persistently obstructs the view of the softtissue landmarks used in the IANB. These three techniques have similarities, and each has advantages and disadvantages [11].
