摘取方式对铸造三臂卡环固位臂应力影响的三维有限元研究

摘要

Objective To investigate the influence of two denture removing methods on the retention of three-arm casting clasps.Methods Three-dimensional finite element models of the abutment and retention arms with different widths and depths of undercut were established.Dynamic displacement load (3mm/s) was exerted on the middle and the end of the retentive arms to test the stress in retention arms while they were being removed from the abutment.Results When the denture was being removed by pulling the base, the peak stress in retentive arm of cast Co-Cr alloy and gold alloy with different width was positively correlated to the undercuts depth displaced by clasp tips.The increase of peak stress of retentive arms with similar location of clasp tips and material was significantly related to the increase of the arm width.The increase of peak stress of retentive arms with similar width and different material was significantly related to the increase of undercuts depth displaced by clasp tips.The phenomenon was common for the gold alloy and Co-Cr alloy clasps while denture was being removed by pulling the clasp.With the increase of undercuts depth displaced by clasp tips, the peak stress in retentive arm of the same width and material increased more quickly while denture was being removed by pulling the clasp than by pulling the base.Conclusion The removable partial denture (RPD) of cast Co-Cr alloy was fit to be removed by pulling the clasp.The RPD of cast gold alloy was fitter to be removed by pulling the clasp than by pulling the base while the undercuts depth displaced by clasp tips was small, and it was fitter to be removed by pulling on base than by pulling on clasp while the undercuts depth displaced by clasp tips was large.%目的 用三维有限元方法分析钴铬合金和金合金铸造三臂卡环固位臂在不同摘取方式时的应力分布,探讨可摘局部义齿的适宜摘取方式,为临床指导患者摘取义齿提供参考.方法 以下颌第二前磨牙为基牙,建立基牙和三种宽度固位臂的三维有限元模型,设计卡臂尖和固位臂中部进入基牙的倒凹深度不同,分别在固位臂的中部和起始部施加速度为3mm/s的动态位移载荷,使卡环向上产生3mm的位移,计算不同方式摘取时固位臂的接触受力.结果 用推拉基托方式摘取义齿时,三种宽度的钴铬合金和金合金铸造卡环固位臂的最大应力与卡臂尖进入基牙的倒凹深度均呈正相关关系;同种材料的卡环固位臂,当卡臂尖进入基牙的倒凹深度相同时,随着固位臂宽度的增大,最大应力增加,差异有统计学意义;相同宽度、不同材料卡环固位臂,随卡臂尖进入基牙倒凹深度的增大,最大应力增加,差异有统计学意义.用推拉卡环方式摘取义齿时,相关的结果与用推拉基托方式摘取义齿时类似.对于同种材料、同一宽度的固位臂,随着卡臂尖进入基牙倒凹深度的增大,推拉卡环摘取义齿时固位臂的最大应力比推拉基托时增加得快,最大应力拟合直线的斜率大,且两条拟合直线有交点.结论 钴铬合金铸造三臂卡环的可摘局部义齿,适宜用推拉卡环方式摘取.金合金铸造三臂卡环的可摘局部义齿,当卡臂尖进入基牙的倒凹深度较浅时,适宜用推拉卡环的方式摘取;当卡臂尖进入基牙的倒凹深度较深时,适宜用推拉基托的方式摘取.