Establishment of a novel method for qualitative and quantitative evaluation of deglutitive tongue movement by integration of ultrasound video imaging and lateral cephalogram

ABSTRACT Purpose: To establish a novel method for qualitative and quantitative evaluation of deglutitive tongue movement by integration of ultrasound (US) video imaging and lateral cephalogram of mandibular prognathism subjects before and after orthognathic surgery. Materials and methods: The US video imaging and lateral cephalogram were obtained from ten mandibular prognathism subjects before and after orthognathic surgery and integrated with an acrylic positional occlusal plate (POP) as a marker for superimposition. The percentage of the anterior and posterior tongue dorsum height, with respect to the palatal height, was measured and compared at each stage (Stages 1–5) of the deglutitive tongue movement. Individual variation on 5-times repeated deglutitive tongue movement in the same subject was evaluated. Furthermore, the intra- and inter-examiner reliability was evaluated using Dahlberg’s formula and correlation coefficient. Results: The individual variation value was small enough, while the intra-examiner measurement errors were all < 0.20 and the inter-examiner correlation coefficient values were all > 0.80. The percentage of the posterior tongue dorsum height in the postoperative measurement was significantly larger than that measured preoperatively at all deglutitive stages, except Stage 4. In seven out of ten subjects, the tongue tip region protruded over the upper incisor edge before surgery could touch the lingual surface of the upper incisor postoperatively. Conclusion: The newly developed US-cephalogram integration method was useful for qualitative and quantitative evaluation of the deglutitive tongue movement in a clinical setting without additional radiation exposure.