This study was to investigate the effect of posture and force of tongue on the malocclusion by Angle's Classification.
Fifty eight subjects at the age of 7 to 11 who had no congenital orofacial defects-19 of Class I, 19 of Class II and 20 of Class III-were selected. The posture of tongue and hyoid bone was measured by lateral cephalogram taken at rest. Also
pressures of
tongue in swallowing, phonetics and maximum thrust were measured with phsiography and analysed for each group. And lateral cephalogram was taken from the posture and force of tongue were compared with craniofacial variables.
@ES Results of the present investigation led to the following results:
@EN Tongue tips of Class II and III were locate at lower and more posterior positon than that of Class I and the tongue dorsum was located at the lowest position in Class III. There was no difference in position of hyoid bone among Class I, II
and
III.
2. There was no difference of tongue pressure exerted to maxillary incisor among Class I, II and III, but there was the highest tongue pressure of Class III during speech exerted to mandibular incisors.
3. The ratio of upper pressure to lower pressure of the tongue during speech was the highest in Class I followed by Class II and III.
4. Horizontal position of tongue tip at rest position was correlated with ANB. AB plane angle, Posterior facial height of craniofacial measurement in Class I, Y axis to FH plance, FMA in Class II, and SNA, Overjet in Class III.
5. There was correlation between upper and lower pressure of tongue and craniofacial measurements at centric occlusion in each Class.
6. The lower leve of tongue tip and tongue base located, the higher pressure of tongue exerted to loer incisors.
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