Symmetry of the external acoustic meatus: A potential alternative reference plane for three-dimensional imaging in dentistry

Objective: In this study, we thoroughly analyzed how balanced the left and right sides of the external acoustic meatus are. Despite previous research focusing on the consistency of various anatomical features and the shape of the external acoustic meatus, which are important for creating guidelines to assess changes in the skull, there hasn't been enough attention given to how symmetrical it is. Our aim was to fill this gap by providing a comprehensive examination of its bilateral symmetry, which is crucial for accurate evaluations in dentistry and medicine.

Study design: After importing 26 cone-beam computed tomography scans of patients into the ITK-SNAP 3D imaging software, a midsagittal plane was set up as the plane of symmetry for each patient. With this plane, we compared the positions of the most superior and inferior left and right points of the external acoustic meatus. We also compared the lengths and depths of the lines connecting the two points.

Results: There were no statistically significant differences in the position, length, or depth of the external acoustic meatus between the right and left halves of the skull.

Conclusion: Specific points on the skull, such as the highest (most superior MSP) and lowest (most inferior MIP) points, demonstrated a high degree of symmetry in the left and right halves. They demonstrated sufficient symmetry to establish a reliable reference plane. Along with the trajectory connecting them, these points can serve as viable alternatives to the Porion for three-dimensional imaging.