DENTAL ARCH WIDTH AND ARCH LENGTH BEFORE VERSUS AFTER EXTRACTION AND NON-EXTRACTION TREATMENT IN MODERATE DENTITION CROWDING

Objective To investigate the arch widths and arch length changes between before and after treatment by extraction and non-extraction in moderate dentition crowding.Methods Sixty patients with moderate crowding malocclusion in Angle ClassⅠdentition were enrolled and equally divided into extraction group and non-extraction group.For extraction group,MBT was applied;for non-extraction group,self-locking technique was adopted.Models before and after treatment were collected,the arch width of inter-canine,inter-premolar and inter-molar and the length of dental arch of maxilla were measured.ResultsAfter treatment,the inter-canine and inter-premolar width were increased,the inter-molar width and arch length decreased in the extraction group(t=3.25-5.58,P0.05);the inter-canine and inter-premolar width were increased in the non-extraction group(t=3.47,3.49;P0.05).The variation of inter-molar width and arch length after treatment in the extraction group was greater than that that in the non-extraction group(t=3.27,3.33;P0.05).Conclusion The inter-molar width and arch length were decreased by extraction treatment for moderate crowding malocclusion in Angle Class Ⅰdentition.