Changes of symphysis morphology after chincup treatment / 대한치과교정학회지

Although it is well known that the chincup, used to correct a skeletal class III malocclusion in growing children, reduce the mandibular prognathism by arresting the growth of the mandibular length and rotating the mandible posteroinferiorly, the majority of the studies about chincup is focused on condylar head that plays an important role in mandibular growth. The aim of this study was to evaluate the morphologic change of the mandibular symphysis where extraoral force is applied directly during chincup treatment. The data for this study were obtained from lateral cephalometric radiographs of 62 growing children(chincup group:32, control group:30) with mixed dentition who had been accepted for the orthodontic treatment at Chonbuk National University Dental Hospital. The results were as follows : 1. Symphysis height was increased both in chincup therapy group and control group during treatment. Symphysis depth was decreased or maintained the initial values in chin cup therapy group, whereas increased in control group. Posterior symphysis depth was decreased both in chin cup therapy group and control group, but anterior symphysis depth was increased in control group, whereas decreased in chincup therapy group. 2. Chin depth and chin curvature were increased in control group, whereas maintained or decreased in chincup therapy group during treatment. Chin angle, menton angle and symphysis angle were decreased in control group, whereas increased in chincup therapy group. It suggested that bone deposition in pogonion area that occur normally with mandibular growth was suppressed by direct contact of chincup. 3. When growing children wear chincup, symphysis morphology was maintained due to inhibition of forward growth at mandibular symphysis. It may be due to the suppression of bone deposition in anterior part of symphysis.

Dentoalveolar compensation of hyperdivergent skeletal pattern in children and adults / 대한치과교정학회지

Although there is a severe underlying skeletal deformity, the dentition has often maintained some occlusal contact and interdigitation by the teeth compensating in their positions for the skeletal problem, and these dental compensations are manifested in all three planes of space. The purposes of present investigation were 1) to study the pattern of dentoalveolar compensation of hyperdivergent skeletal pattern : and 2) to compare the centoalveolar compensations of hyperdivergent skeletal pattern in children with adults. The samples selected for this study were consisted of 60 subjects in normal group, 60 subjects in hperdivergent group. each was divided into two subgroups by age ; child groups(8~12yr old) and adult groups(17yr old over). The findings of this study were as follows; 1. In child, hyperdivergent subjects had smaller posterior lower facial height(p<0.01) and slightly longer anterior lower facial height than normal ones. In adults, they still expressed smaller posterior lower facial height and much longer anterior lower facial height than normal ones(p<0.01). 2. Hyperdivergent subjects had larger amount of upper and lower incisor relative eruption to their basal bone length than normal ones(p<0.05). In adult, relative eruption of upper incisor was increasing(p<0.05), although relative eruption of lower incisor remained the same as the child. 3. In child, there was no difference between hyperdivergent group and normal one in the upper and lower molar relative eruption to their basal bone length. In adult, hyperdivergent group had larger amount of upper molar relative eruption than normal ones(p<0.01), but relative eruption of lower molar was similar to normal ones. 4. hyperdivergent group had larger angle between lower occlusal plane and mandibular plane than normal group(p<0.01). Upper occlusal plane of adult group rotated more antero-superiorly than child groups, and adult hyperdivergent group had steeper upper occlusal plane than normal group(p<0.05).