The pterygomandibular raphe is a fibrous band running from the pterygoid hamulus of the medial pterygoid plate superiorly to the posterior end of the mylohyoid line on the mandible inferiorly. It marks the boundary between the buccinator muscle anteriorly and the superior pharyngeal constrictor posteriorly, with both muscles taking origin from it. It forms the visible fold behind the last molar tooth in the oral cavity.
Provides the common origin for the buccinator and superior pharyngeal constrictor muscles; marks the pterygomandibular space lateral to it; creates the palpable fold behind the retromolar triangle that guides inferior alveolar nerve block injection.
The pterygomandibular raphe is the primary landmark for inferior alveolar nerve block (IANB): the needle is inserted lateral to the raphe fold at the level of the pterygomandibular space, targeting the mandibular foramen on the medial ramus. The space lateral to the raphe and medial to the mandibular ramus (pterygomandibular space) contains the inferior alveolar nerve and vessel. In peritonsillar abscess drainage, the anterior pillar and the pterygomandibular raphe guide the incision site. Oral tumours involving the retromolar trigone spread along the raphe into the pterygomandibular space.
The pterygomandibular fold (overlying the raphe) is the key intraoral landmark for inferior alveolar nerve block: the needle is inserted at the level of the mid-raphe, lateral to the fold, and advanced 20-25 mm to contact the medial ramus just above the mandibular foramen where the IAN lies before entering the mandibular canal.
