Is it possible to reveal a typical swallowing pattern for specific skeletal malocclusion types using M-mode sonographic imaging of tongue movements?

Purpose: The present study aims to compare the M‑mode ultrasound findings of different skeletal malocclusions and to evaluate whether sonographic parameters can be used for the diagnosis of malocclusions.

Methods: Tongue movements of 36 adolescents aged between 10.37 and 17.29 years (mean 14.25 ± 1.78 years) were assessed using simultaneous two-dimensional real-time B‑mode and M‑mode sonography. The swallowing patterns of the subjects were visualized recording the motion of the tongue surface in the ultrasound images utilizing a fixed scan line through the middle of the tongue. M‑mode scans of tongue motion during empty deglutition were recorded. The parameters range, duration, and speed were computed for the entirety of the swallowing process using M‑mode examination. Findings were evaluated and statistically analyzed.

Results: No clear intraindividual repeatability in the M‑mode imaging of the subjects' swallowing process could be observed. Considering the setup used in the study, it was not always possible to distinguish individual swallowing stages in the M‑mode images with regard to the chosen reference points. The average duration, range of motion, and speed of swallowing were found to be 2.43 s, 24.06 mm, and 10.34 mm/s, respectively. The findings showed both intra- and intersubject variability during empty swallowing.

Conclusion: With the help of the metrics that could be calculated based on the M‑mode images, it was not possible to differentiate the swallowing acts of different skeletal malocclusion types. It remains unclear whether M‑mode imaging can accurately visualize the swallowing pattern. Therefore, further progress in technology and multidisciplinary work is needed in order to establish diagnostic references regarding swallowing.