模拟正畸牵引术联合肩领设计对残根抗折力的影响

目的 探讨不同高度的牙本质肩领设计对预成碳纤维桩核修复后牙体抗折力的影响.方法 24颗完整、离体、单根管下颌第一前磨牙于颊侧釉牙骨质界上1.0 mm处截冠,经根管治疗后制备残根模型.通过模拟正畸牵引术(牙合)向牵引残根并在残根颈部预备一定高度的牙本质肩领；按预备的牙本质肩领高度不同(0.0、1.0、2.0 mm)依次分为A、B、C三组,预成碳纤维桩核联合铸造全冠修复残根.试件自全冠颈缘完成线下2.0 mm包埋于自凝塑料内,电子万能试验机以与牙长轴成150°、横梁位移速度1.0 mm/min于颊尖顶加载,测定折裂载荷并进行统计分析.结果 三组试件的折裂载荷(kN)均值依次为(1.13±0.15)、( 1.63±0.14)、(1.92±0.19).预备牙本质肩领可显著提高牙体的折裂载荷(F=48.437,P＜0.001)；并且随着预备的牙本质肩领高度增加,牙体的折裂载荷显著增大(P＜0.05).结论 在残根颈部设计牙本质肩领,可明显提高牙体的折裂载荷.

Effect of simulated forced eruption and ferrule design on the fracture resistance of the residual roots restored with prefabricated fiber post-and-core system

Objective To evaluate the effect of different ferrule lengths on the fracture resistance of residual roots restored with carbon fiber post-and-core system.Methods 24 extracted,intact mandibular first premolars were endodontically-treated,and sectioned 1.0 mm coronal to the buccal cementoenamel junction(CEJ) for the preparation of the residual-root model.The simulated forced eruption method was done for the ferrule design in the cervical tooth structure.All the residual root models were randomly divided into three groups according to the ferrule length from 0 mm to 2.0 mm with 1.0 mm interval each(group A,B and C).After restoration with prefabricated carbon fiber post-and-core system,each specimen was embedded in a self-curing acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown,then loaded at 150 degrees from the long axis in a universal testing machine at the crosshead speed of 1.0 mm/min until fracture.Data were recorded and analyzed using ANOVA and Tukey HSD tests,and Fisher’s exact test.Results Mean failure loads(kN) for A,B,C groups were:1.13(S.D.0.15),1.63(0.14) and 1.92(0.19).Significant differences were shown for the effect of ferrule design(F=48.437,P < 0.001),and among the three groups(P < 0.05).Conclusion The design of an 1.0 to 2.0 mm long ferrule placement on the apical crown margin resulted in a significant increase in fracture resistance of residual roots.