Application Of Free-edge System In Orthodontic Treatment

Objective:The purpose of this study was to explore the differences of the dento-skeletal and soft tissue profile changes between Free-edge and Begg appliance in class II subjects,and to evaluate dento-skeletal and soft tissue changes in skeletal class III subjects in permanent dentition who had the lower third molars extracted and were treated with Free-edge appliance .Methods:21 patients treated with Free-edge appliance and 20 patients treated with Begg appliance were included in the study. Each patient had a class II division 1 malocclusion and had the four first premolar extracted as part of the treatment design.Cephalometric evaluation before and after treatment were compared both among and between the two groups.14 patients in permanent dentition with skeletal ClassⅢmalocclusion had their lower third molars extracted and treated with Free-edge appliance were included in the study.Cephalometric analysis was used to evaluate the changes before and after treatment.Result:1.Changes in Free-edge group: No statistical difference were found for items of SL,S-Ptm, Ptm-ANS, SNB,SN-MP, anterior facial height(N-Me), L1-MP(deg) , (S-Go/N-Me), L1-NB(deg).The linear measurements of U1-PP,U6-PP and L6-MP, and the angular measurements of OP-SN,Z angle were increased(p<0.01),while SNA,L1-MP(mm),U1-SN ,Ls-E-line,Li-E-line, overbite, and overjet were reduced after treatment(P<0.01).Changes in Begg treatment group: Such items of OP-SN, U1-PP(mm), U6-PP,L6-MP were increased(p<0.01). SNA , overjet and the distance of L1-MP(mm)were reduced(p<0.01), while those measurement of SNB ,MP-SN, and (S-Go/N-Me) did not show statistical significant difference.Comparison between groups: No statistical differences were found between changes in Free-edge and Begg treatment group.2. Changes in skeletal classⅢsubjects by lower third molars extraction and Free-edge appliances treatment:No significant difference were found in items of L6-PP distance, mandibular plane(SN-MP),posterior/anterior facial height ratio(S-Go/N-Me ),SNB, maxilla and mandible length before and after treatment. SNA, ANB, U1–SN angle,L1–MP distance,U6-PP distance, L6-MP angle,U1- FHV distance,L 6- FHVdistance,upper lip to E-line distance were significantly increased (P<0.05), while L1- FHV,U6- FHV,OP-SN,L1-MP(deg) ,L1 to E line were reduced after treatment(P<0.05).Negative value of the distance difference of upper lip and lower lip to Sn-Pg'at the beginning of treatment changed to positive value with significant difference(P<0.001).Conclusion:After Free-edge and Begg treatment ,the upper and lower molars and the upper anterior teeth were extruded while the lower anterior teeth were intruded among the two groups, thus might explain the clockwise rotation of occlusion plane. The mandibular plane showed no significant change. No statistical differences were found in changes before and after treatment between Free-edge and Begg group.Dento-alveolar compensation was the main change after extraction of lower third molars and treatment using Free-edge appliances in skeletal classⅢmalocclusion in permanent dentition ; Occlusal plane was flattened and counterclockwise rotated.The patients profile was much improved, but treatment did not change sagittal and vertical skeletal pattern.