Identification of a deepest oblique layer within the layered architecture of the buccinator muscle at the parotid duct penetration site.

The buccinator muscle plays an important role in mastication, swallowing, and facial expression, yet its detailed fiber architecture, particularly at the site where the parotid duct penetrates the muscle, remains insufficiently defined. This study aimed to elucidate the three-dimensional organization and layered structure of the buccinator muscle at the parotid duct penetration site. Fifty hemifaces from embalmed adult cadavers (22 Korean, 3 Caucasian) were examined by meticulous microdissection under a surgical microscope. The buccinator fibers surrounding the parotid duct consistently formed a crossing pattern, with superior bundles coursing obliquely downward and inferior bundles running obliquely upward, intersecting around the ductal penetration site. A previously unrecognized deepest oblique layer was identified below the duct, attaching mainly to the inferior vestibular and commissural mucosa. This deepest layer formed part of a multilayered architecture together with the intermediate transverse and superficial oblique fibers. These findings demonstrate that the buccinator muscle–parotid duct region constitutes a structurally reinforced and functionally adaptive unit that supports salivary regulation and intraoral pressure control. Understanding this multilayered organization provides valuable anatomical insight for optimizing buccinator muscle-based reconstructive flap design and preserving functional integrity during intraoral surgery.