The Study Of Quick Self-ligating Appliance System And MBT System On Correlating Maxillary Arch And Alveolar Arch During The Leveling And Aligning Phase In Clinical Orthodontic Treatment

Objective The purpose of this study is to evaluate the effects produced by Quick self-ligating appliance system and MBT system in non-extraction and extraction therapy on the change of maxillary arch and alveolar arch during leveling and aligning phase through clinical models, cephalograms measurement and clinical observation. And the clinical effect of size difference on maxillary and alveolar archAlso the mechanism variance on changing maxillary and alveolar arch of both systems is explored.Methods90patients who were taking orthodontic treatment using Quick self-ligating appliance system (FORESTADENT, Germany) and3M MBT in Orthodontic Department of Stomatology Hospital Affiliated Kunming Medical University in each group were selected. All patients aged13-17years old,14.4years old on average, and complicated with mild to severe maxillary arch crowding. All patients were divided into two groups:group A included patients were complicated with mild to moderate maxillary arch crowding and were performed non-extraction treatment; and group B included patients with severe congestion treated by the removal of the bilateral first premolar appliance.0.012,0.016,0.016×0.022,0.018x0.025inch Heat Activated Nickel-titanium Arch wire (FORESTADENT, Germany) were used leveling and aligning in all patients. Occlusal plane analysis was used to determine whether leveling aligned phase completed, Quich auto-lock group(A group) and MBT group (B group)were set, further groups set by size details: non-extraction0.016inch heat activated nickel-titanium arch wire (Al agroup, B1agroup),0.016×0.022inch (A2group,B2group),0.018×0.025inch(A3group, B3group); Maxillary models were made and photo cephalograms were measured, the width and length of tooth arch and maxillary arch were measured, including anterior inclination pre-post orthodontic and aligning. Datas were analyzed by Paired T-test,x2test in SPSS20.0.Results In non-extraction treatment group, anterior inclination, the width and length of tooth arch and maxillary arch all increased in different levels after aligned by Quick and MBT system with different size heat-activated nickel titanium wire. No statistical difference was shown between0.016inch (Al, B1) and0.016×0.022group (A2, B2) except a more anterior inclination found in Quick than MBT system(P>0.05); a statistical difference about first molar gingival wideth, maxillary arch length and circle length was shown between0.018×0.025group(A3, B3) and B3group (P<0.05).Anterior inclination and posterior arch length decreased, arch length between maxillary canines and maxillay arch increased, meanwhile, maxillay arch length and arch perimeter decreased largely. No statistical difference was shown between0.016inch group(Al, B1)(P>0.05). Statistical difference about width between canine cusp was shown between0.016×0.022inch group(A2, B2), more width between canine cusp in A2than B2was seen(P<0.05). In0.018×0.025group(A3,B3), width decrease of alvelor of second molar, arch length and arch perimeter in A3group was less than B3group, a statistical difference was shown(P<0.05).Conclusions:1. In non-extraction level aligning, both systems showed expansion effect on arch length; Quick self-ligating appliance system got larger expansion effect than MBT system, statistical difference existing.2. In extraction level aligning, both systems eased crowding by expanding canines arch and maxillary arch, moving anterior teeth into the extraction space. Quick system showed a better effect on arch expanding than MBT system, and more protection on posterior support with a statistical difference. 3. arch and alveloar arch expanding effect is different from each other for two systems in leveling.