[The analysis of the changes of tongue shape and position, hyoid position in Class II, division 1 malocclusion treated with functional appliances (FR-I)].
OBJECTIVE
The objective of this study is to analyze the changes of tongue shape and position, hyoid position with FR-I therapy in class II, division 1 malocclusion.


METHODS
12 patients with class II, division 1 malocclusion treated with FR-I appliance(8 male, 4 female, average 11 years old) were chosen. The acceptable standard of this experiment was an horizontal growth pattern with normal maxilla, retracted mandible and short lower facial height. The average period of treatment was about 8 months. The assessment was made from a lateral cephalogram taken in habitual occlusion before and after treatment. The shapes and sizes of tongue can be measured from the occlusal films with template. These seven lines from six angles of 30 degrees which can be marked in millimeter. Fig 2 showed the reference points and lines: Is1 (the incisal margin of the lower incisors), Mc (the tip of the distobuccal cusp of the lower fist molar), V(the most caudal point on the shadow of the soft palate or its projection onto the reference line). Is1 connected Mc by a straight line extended to V to form the reference lines. After the lines were constructed, the middle point between Is1 and V was called O, and a perpendicular line was constructed from it to the palate contour. The baseline of the template was coincided with the constructed reference line, and the vertical line intersected the reference line at O. The template was placed over the constructed lines, and the exact measurements of the root, the dorsum and the tip of tongue were taken. This was done along the seven constructed lines, and the measurement gived a relative size of the tongue(e.g. the size related to the oral cavity).


RESULTS
After treatment, the shape of tongue changed as a result of the increase of oral cavity. There was a tendency that the position of the tongue shifted forwarded and the tip of tongue lied further forward. At the same time, the position of hyoid moved forward in a horizontal dimension and downward in a vertical dimension.


CONCLUSIONS
It confirms that the therapeutic mechanism of FR-I is to induce an anterior shift of mandible and lead to a forward position of tongue, hyoid and cervical soft tissue, which modify the saggital relationship of jaws. The shape of tongue changes due to the increase of oral cavity.
Zhou
L
L
College of Stomatology, West China University of Medical Sciences.
Zhao
Z
Z
Lu
D
D
D002648:Child; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000503:physiopathology*; D008297:Male; D008312:Malocclusion, Angle Class II / Q000503:physiopathology / Q000628:therapy*; D017289:Orthodontic Appliances, Functional; D013284:Stomatognathic System / Q000503:physiopathology; D014059:Tongue / Q000503:physiopathology*