Intraoral Ultrasonographic Anatomy of the Floor of the Mouth: Implications for Image-Guided Procedures

Abstract

Intraoral ultrasonography (IOUS) is a simple, rapid, and safe imaging technique, yet its clinical use in the oral cavity has been limited due to the region's complex anatomy and the absence of standardized anatomical reference data. The floor of the mouth (FOM) contains the submandibular duct, salivary glands, vessels, and multiple muscles within only a few millimeters of soft tissue, making precise anatomical knowledge essential for diagnosis and safe surgical intervention. This study aimed to analyze IOUS patterns of the FOM to identify key anatomical structures and provide depth-based anatomical data that enhance the clinical applicability of IOUS. Using a 12 MHz intraoral linear transducer, ultrasonographic images were obtained from 84 sides in 42 volunteers (12 male and 30 female; mean age, 34.0 +/- 12.5 years) at three standardized intraoral reference points. The key structures were visualized in real time using B-mode and Doppler imaging, and their depths from the oral mucosa were quantitatively measured. The submandibular duct was consistently observed at P1 and P2 and located superficially at approximately 2 mm. In contrast, the lingual and sublingual vessels were located much deeper (approximately 7-11 mm) and showed substantial variability. No significant differences were observed between sides, between sexes, or between arterial and venous depths. The arterial and venous depths showed considerable overlap, indicating a single "vascular layer," which closely corresponds to previously reported lingual nerve depths in cadaveric studies. These findings define an in vivo neurovascular corridor between the duct and vascular layer, providing critical guidance for safe surgical access. Overall, this study provides essential baseline data for the IOUS anatomy of the FOM, which can improve diagnostic accuracy and guide safer minimally invasive procedures in clinical practice.