【作者】 罗小安；

【导师】 林珊；

【作者基本信息】 福建医科大学 ， 口腔临床医学， 2004， 硕士

【摘要】 目的:主要研究口腔环境中采用滑动机制内收前牙及远移尖牙阶段正畸不锈钢弓丝机械性能、表面摩擦力及表面形构的变化。材料与方法:选择两种不同0.019”*0.025”不锈钢方丝(分别标记为A和B)及两种不同0.020” 不锈钢圆丝(分别标记为C和D)。使用后的A和B取自一组恒牙早期拔牙矫治病例的前牙内收阶段,使用后的C和D取自另一组恒牙早期拔牙矫治病例的尖牙远移阶段。每一使用后的弓丝均截取其两侧尖牙远中区域,作为检测样本。使用前的弓丝及上述检测样本分组如下:T0(使用前,对照组),T1(使用4周),T2(使用8周),T3(使用12周),T4(使用16周),T5(使用20周),每组各取n=20(n代表弓丝段数)。选择弹性模量、屈服强度、挠度作为评价不锈钢弓丝机械性能的指标,其中弹性模量、屈服强度采用万用材料检测机检测,挠度采用挠度检测装置检测。选择静摩擦系数评价不锈钢弓丝表面摩擦力的变化及其对弓丝与托槽(和颊管)之间滑动摩擦阻力的影响,采用摩擦力检测装置检测。采用扫描电镜观察不锈钢弓丝使用前后表面形构及粗糙度的变化。结果:1、前牙内收阶段,0.019”*0.025”不锈钢方丝A和B在口腔内使用4周、8周、12周、16周及20周后,弹性模量、屈服强度及挠度变化无显著性意义(P>0.05);使用4周、8周后,静摩擦系数变化无显著性意义(P>0.05),<WP=4>但使用12周、16周及20周后,静摩擦系数变化有显著性意义(P<0.01),随时间延长逐渐增大;使用20周后,表面明显粗糙,凹凸不平。2、尖牙远移阶段,0.020”不锈钢圆丝C和D在口腔内使用4周、8周、12周、16周及20周后,弹性模量、屈服强度及挠度变化无显著性意义(P>0.05);C使用4周后和D使用4周、8周后,静摩擦系数变化无显著性意义(P>0.05),但C使用8周、12周、16周及20周后,D使用12周、16周及20周后,静摩擦系数变化有显著性意义(P<0.01),随时间延长逐渐增大;使用20周后,表面明显粗糙,凹凸不平。结论:用于前牙内收阶段的0.019”*0.025”不锈钢方丝A和B及用于尖牙远移阶段的0.020”不锈钢圆丝C和D在发挥作用时,尽管处于复杂的口腔环境中,受到许多因素影响,但在使用4周、8周、12周、16周及20周后,机械性能变化无显著性意义,说明弓丝A、B、C、D在口腔内使用4周、8周、12周、16周及20周期间,一直保持有足够的刚性、强度、抗挠曲能力,可作为维持性弓丝起良好的稳定和引导作用,有利于前牙顺利内收或尖牙顺利远移。但0.019”*0.025”不锈钢方丝A和B及0.020”不锈钢圆丝D使用12周、16周及20周后,0.020”不锈钢圆丝C使用8周、12周、16周及20周后,表面摩擦力均随时间延长逐渐增大,提示在其他影响因素相同的条件下,滑动法内收前牙或远移尖牙过程中弓丝与托槽(和颊管)之间的摩擦阻力也相应增加,可能消耗更多支抗,牙齿移动效率也会降低。使用20周后的弓丝A、B、C、D,表面明显粗糙,凹凸不平,说明弓丝表面形构发生显著改变,粗糙度明显增大,从而可能增加牙齿移动过程中的滑动摩擦阻力。更多还原

【Abstract】 Objective: The main purpose of this study was to investigate the changes in mechanical properties , surface frictional forces and surface topography of various orthodontic SS arch wires used in the anteriorteeth-retraction or canine-distalization period .Materials and Methods: Two types of 0.019×0.025-in rectangular SS arch wires ( marked with A and B respectively ) and two types of 0.020-in round SS arch wires ( marked with C and D respectively ) used in the comprehensive treatment with four first premolars extracted were selected .The posterior portion of each wire was segmented . The unused segments and these used ones were separated into 6 groups respectively : as-received condition ( T0 , control group ) , exposed to oral conditions for 4 weeks ( T1 ) , for 8 weeks ( T2 ) , for 12 weeks ( T3 ) , for 16 weeks ( T4 ) and for 20 weeks ( T5 ) . Changes in yield strength and modulus of elasticity were observed by tensile testing , and deflections were tested by deflection test , and static frictional coefficients by friction test . Surface topography was assessed by scanning electron microscope ( SEM ) . Results: Our findings showed that there were no statistically significant differences between the unused wires and the ones exposed to oral conditions <WP=6>for 4 , 8 , 12 , 16 , 20 weeks in yield strength , modulus of elasticity , and deflection ( P >.05 ) . Two types of 0.019×0.025-in rectangular SS arch wires ( i.e. A and B ) and 0.020-in round SS arch wire D showed no significant differences in static frictional coefficients after they were exposed to oral conditions for 4 , 8 weeks ( P >.05 ) , but demonstrated significantly greater static frictional coefficients compared with the control wires after their intraoral exposure for 12 , 16 , 20 weeks ( P <.01 ) . However , the static frictional coefficient of 0.020-in round SS arch wire C was greater than that of the control group after their exposure to oral conditions for 8 , 12 , 16 , 20 weeks ( P <.01 ) . Surface roughness of the wires A,B,C,D exposed to oral environment for 20 weeks was significantly greater than that of the control wires .Conclusions: During the anteriorteeth-retraction or canine-distalization period , the mechanical properties of 0.019×0.025-in rectangular SS arch wires A and B and 0.020-in round SS arch wires C and D weren’t affected significantly by many oral environmental factors . It indicated that all these SS arch wires could stable the dentition and guide the tooth movement well when they were exposed to oral conditions for 4 , 8 , 12 , 16 or 20 weeks . However , oral conditions affected the surface structure of these SS arch wires and then increased their surface roughness and the frictional forces between brackets and wires after their exposure to oral environment for 12 , 16 , 20 weeks ( A , B , D ) or 8 , 12 , 16 , 20 weeks ( C ) . The greater friction opposed the free sliding action of teeth guided on appropriately shaped SS archwires .更多还原