Preliminary study of articulatory characteristics in open bite subjects revealed by 3T magnetic resonance imaging movies

Abstract

Objectives: Previous studies have reported that articulatory dysfunction accompanied by a certain type of malocclusion can be improved by orthodontic treatment. We developed a 3-T magnetic resonance imaging (MRI) movie method with tooth visualization that can display the dynamic movement of articulation without radiation exposure. To the best of our knowledge, there is currently no report on the possible differences in articulatory movement between subjects with a normal occlusion and those with malocclusion using the 3T MRI movie method. Thus, the objective of this study was to examine the articulatory difference between subjects with a normal occlusion and those with an open bite using an MRI movie. Materials and Methods: Twenty healthy adult females, ten with a normal occlusion and ten with an anterior open bite were recruited. The overbite of the open bite subjects was zero or smaller, and all of them exhibited a tongue-thrusting habit during swallowing. A turbo spin echo image with a contrast medium was used to visualize the anterior teeth, and articulatory movement during articulation of the vowel-consonant-vowel syllable (/asa/) was scanned. The difference in tongue movement between subjects with a normal occlusion and those with an open bite was compared by measuring seven variables. Moreover, the distance between the incisal edge and the tongue apex during articulation of /s/ and the speech duration were compared. Furthermore, frequency analysis on /s/ by fast Fourier transform power spectrum was performed. Results: The tongue apex of the open bite subjects moved more anteriorly than that of the normal subjects. However, there was no significant difference in the phonetic analysis between subjects with a normal occlusion and those with an open bite. Conclusion: The 3-T MRI movie was an efficient method to quantify articulatory tongue movements. Although there was a difference in tongue movement during swallowing between subjects with a normal occlusion and those with an open bite, the difference in the articulatory tongue movements was minimal, suggesting it could be a functional compensation.