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Objective:1. To explore the clinical significane in skeletal class III malocclusion in early permanent dentition who had the lower third molars enucleated, so as to provide clinical basis for the treatment of class III malocclusion.2. Research the application features of Free-edge technique in the treatment of skeletal class III malocclusion.Methods:Select 24 patients of 12.5-15 years old skeletal class III malocclusion who were treated with the Free-edge appliance, 15 patients had the the lower third molar extracted as part of the treatment design (the extraction group); 9 patients treated only with the Free-edge appliance(the no-extraction group). Cephalometric evaluation before and after treatment were compared both among and between the two groups.Result:Changes in the extraction group: SNA, ANB, FCA angle and Wits, Ar-Go, Go-Me, UL-SnPg’-LL-SnPg’distance were significantly increased (P<0.01); APDI, NLA angle and the distance from Pog’to Pog were reduced after treatment (P<0.05). No significant difference were found in items of B-SFH distance, mandibular plane (FH-MP). posterior/anterior facial height ratio (S-Go/N-Me), SE, SL, B6-PR distance, SNB angle before and after treatment (P>0.05). Changes in the no-extraction group:?SNA, ANB, U1/ SN, FCA, L6/ MP angle and UL-SnPg’-LL-SnPg’, Wits, Ar-Go, Go-Me, B-SFH, B6-PR distance were increased (P<0.05); APDI, L6/ MP, NLA angle and the distance from Pog’to Pog were reduced after treatment (P<0.05). No significant difference were found in items of SNB, mandibular plane, S-Go/N-Me, LL-Sn Pg’distance before and after treatment (P>0.05).The compares of difference before and after treatment between the two groups: ANB, U1/SN, L1/MP, L6/MP angle and LL-SnPg’, Wits, Ar-Go, Go-Me, B-SFH, B6-PR and the distance from Pog’to Pog have significant difference (P<0.05).Conclusion:1. Enucleating the lower third molars can provide the clearance for the whole dentition distal movement and vertical in the treatment of skeletal class III malocclusion .2. Free-edge appliance can give the dentition tipping movement first, achieve distal movement of the whole dentition by the Root Control auxiliary arch second.3. When correcting the anterior crossbite and class III occlusion, the cxtraction group depends mainly on the whole dentition distal movement and vertical while the no-extraction group was approached by the pour lip of the maxillary anterior teeth and the distal vertical of the mandibular dentition.4. Whether or not extraction, the Free-edge technology can make a remarkable soft-tissue change in the treatment of the moderate skeletal class III malocclusion.
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