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The pterygomandibular fossa is a fascial space that encloses vital structures including the inferior alveolar nerve (IAN), which is the largest branch of the mandibular division of the trigeminal nerve. The IAN enters the mandible through the mandibular foramen and provides sensory innervation to the teeth of the lower jaw. Oral health professionals need to appreciate the anatomy of the pterygomandibular fossa in order to achieve successful inferior alveolar anesthesia during oral surgery as well as implant placement and third molar extraction. Anatomical variations of the pterygomandibular fossa can influence the success of mandibular or alveolar blocks leading to inadequate anesthesia. Bifid mandibular foramina are a common anatomical anomaly encountered in patients with failed inferior alveolar blocks. The incidence of bifid mandibular foramina has been estimated by many studies to vary from 0.05% to 65% in the general population. Bifid mandibular foramina can occur unilaterally or bilaterally on the mandible. The prevalence, clinical significance and anatomy of a bifid mandibular foramen will be reviewed in this article.