RESUMO
<p><b>OBJECTIVE</b>To investigate the hard and soft tissue changes following the treatment of Class II division 1 malocclusion using Twin-block appliance.</p><p><b>METHODS</b>50 Class II division 1 malocclusion subjects whose handwrist radiographs were in FG-G stage were selected. One group (27 patients) was treated with Twin-block appliance, the other group (23 patients) was observed without treatment The acquired data of cephalometric of two groups were analyzed statistically with SPSS 11.0.</p><p><b>RESULTS</b>Soft tissue changes, Ls-E, Li-E, U1-Stms, Stms-Stmi, NsLs-FH, LsNsLi, LsNsPg', the angle of H decreased. Sn-Stms, Stmi-Me', Ns-Me', Sn-Me', NsLi-FH, NsPg'-FH, A'Ls-FH, B'Li-FH, LiB' Pg', CmSnLs, GSnPg', the angle of Z increased, there was statistically significant difference (P < 0.05). Hard tissue changes, SNB, L1-NB, IMPA increased, ANB, U1-SN, U1-NA, FMIA decreased, there was statistically significant difference (P < 0.05).</p><p><b>CONCLUSION</b>Sagittal relationship between upper- and lower-jaws is effectively improved after orthopedics with Twin-block appliance. Lower face height increases. Soft tissue profile tends to be straight-styled.</p>