边缘形式对大面积缺损第一磨牙髓腔固位冠应力分布的影响

Research on the Biomechanical Effects of Restoration Method on First Molar with Significant Loss of Coronal Structure

目的:探讨下颌大面积缺损第一磨牙经根管治疗后,采用髓腔固位冠修复,其边缘设计形式对牙体组织及修复体力学的影响。方法:建立右侧下颌第一磨牙的三维有限元模型,磨牙存在牙冠大面积缺损,根管治疗后采用髓腔固位冠修复,设计2种边缘预备形式,即90°边缘和对接边缘,对模型进行加载,观察各部分的最大主应力(εMax)。结果:2种修复方式下,牙体和修复体的应力集中区域有所不同。其中牙釉质和修复体的应力受边缘设计因素的影响较大。在垂直载荷下,釉质的εMax峰值在对接边缘组较90°边缘组下降了42.88%,应力集中分别位于边缘的釉牙本质界处和边缘的釉质表面。在垂直载荷下,全瓷修复体的εMax峰值在对接边缘组较90°边缘组下降了45.55%,应力集中分别位于边缘近髓腔区域和边缘近牙体表面。在舌颊向载荷下,全瓷修复体的εMax峰值在对接边缘组较90°边缘组下降了12.58%,应力集中分别位于髓腔底部和边缘近牙体表面。结论:在髓腔固位冠的设计中,对接边缘的设计形式更有利于保护牙釉质和改善修复体的应力,从生物力学角度对修复体的稳定性起到积极的作用。

Objective：To study the biomechanical effects of margin design on tooth tissue and dental prostheses on mandibular first molar with significant loss after root canal treatment（RCT）.Methods：3Dfinite element models of the right mandibular first molar with significant loss of coronal structure was established.After RCT,the loss was restored by endocrown,with two kinds of margin design.The models were loaded and maximum principal stress（εMax）of each part was observed.Results：Stress concentration in tooth and prostheses was different in these two kinds of restoration.Stress in enamel and prostheses were tend to be affected by margin design.Under vertical loading,peak value of enamelεMax in butt-joint margin group was 42.88%lower than that of the 90°margin group,with stress concentrating on dentino-enamel junction and enamel surface near margin area.Under vertical loading,peak value of ceramicεMax in butt-joint margin group was 45.55%lower than that of the 90°margin group,with stress concentrating on retention cavity inside the pulp chamber and tooth surface near margin area.Under lingualbuccal loading,peak value of ceramicεMax in butt-joint margin group was 12.58%lower than that of the 90°margin group,with stress concentrating on the bottom of the pulp chamber and tooth surface near margin area.Conclusion：Endocrown with butt-joint margin design was helpful to protect enamel and improve stress distribution of the prostheses.And from the view of biomechanics,it was positive to insure long-term stability.