Research Of Changes In Surface Frictional Forces And Surface Topography Of Orthodontic Archwires Exposed To Oral Conditions In Different Phase

Objective:The main purpose of this study was to investigate the changes in surface frictional forces and surface topography of various orthodontic archwires exposed to oral conditions in different phase.Materials and method:1.The testing maxillary model was ClassⅠmalocclusion with mild crowding.Conventional brackets of MBT producted by 3M Company was bonded to the model.The static and kinetic friction resistance of the bracket and each wire(new 0.014 and 0.016 inch NiTi archwire;0.014 and 0.016 inch NiTi archwire used 1 month;0.014 and 0.016 inch NiTi archwire used 2 month-producted by Beijing nonferrous metal Company )couple was examined in the alignment phase.2.The testing model was severe crowding malocclusion treated by extraction. Conventional brackets of MBT producted by 3M Company was bonded to the model. The static and kinetic friction resistance of the bracket and each wire (new 0.019×0.025 ss archwire;0.019×0.025 ss archwire used 4 weeks;0.019×0.025 ss archwire used 8 weeks;0.019×0.025 ss archwire used 12 weeks;0.019×0.025 ss archwire used 16 weeks;0.019×0.025 ss archwire used 20 weeks-producted by 3M Company)couple was examined in the space closure phase.3.Surface topography of each type archwire was assessed by scanning electron microscope(SEM).Result:1.NiTi archwire:In the alignment phase , surface frictional forces of 0.014 and 0.016 NiTi archwire has a little increasing after they were exposed to oral condition for 1 month(P<0.05);but demonstrated significantly greater surface frictional forces compared with the control wires after their intraoral exposure for 2 month(P<0.01).2.0.019×0.025 ss archwire:In the space closure phase,0.019×0.025 ss archwire showed no significant differences in surface frictional forces after they were exposed to oral conditions for 4,8 weeks(P>0.05);and a little increasing after they were exposed to oral condition for 12 weeks (P<0.05); but demonstrated significantly greater surface frictional forces compared with the control wires after their intraoral exposure for 16,20 weeks (P<0.01).3.SEM:The surface topography of NiTi archwire and stainless steel archwire were not smooth and glossy,sometimes there was mild scoring and depression.Surface roughness of the archwire exposed to oral environment was significantly greater than the new one.Conclusion:The study shows:1.In the alignment phase, 0.014 and 0.016 inch NiTi archwire should replace with a new one after used 2month.2.In the space closure phase, clinician should pay close attetion to increasing anchorage after 0.019×0.025 ss archwire used 3month.3.surface roughness of orthodontic archwire was greater than the new one.