不同桩核和箍结构与牙根抗力的实验研究

The effect of ferrule length on fracture resistance of endodontically treated teeth restored with different post-and-core materials

目的研究不同材料桩核及箍结构对牙体抗折强度的影响。方法32颗完整离体下颌第一前磨牙于颊侧釉牙骨质界上1mm处截冠,制备残根模型;按桩核材料及箍结构不同分为四组:铸造桩核无箍结构组(A1组)、铸造桩核有箍结构组(A2组)、纤维桩无箍结构组(B1组)、纤维桩有箍结构组(B2组)。所有试件自铸造全冠颈缘完成线下2mm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1.0mm/min于颊尖顶加载,测定断裂载荷并进行统计学分析(а=0.05)。结果四组试件的折裂载荷均值(KN)依次为:1.46±0.45、1.07±0.21、1.13±0.30、1.02±0.27。铸造桩核无箍结构组表现出显著高的折裂载荷(P<0.05)。桩核材料对试件的破损模式亦有显著的影响(P<0.05)。结论残根桩核修复时,采用牙冠延长术设计2mm高的箍结构,降低了修复后牙体的抗力;使用预成纤维桩联合复合树脂核修复有利于保护残根。

Objective To investigate the effect of a crown lengthening ferrule on the fracture resistance of endodontically treated teeth restored with two dowel - core systems. Methods Thirty - two extracted mandibular first premolars were each sectioned perpendicular to the long axis at a point 1.0mm occlusal to the buecal cementoenamel junction. Following endodontic treatment, the teeth were assigned randomly to 4 groups： cast Ni - Cr alloy dowel - core with no ferrule （Group A1 ）, cast dowel - core with 2.0mm ferrule （Group A2）, prefabricated carbon fiber - reinforced dowel- resin core with no ferrule （ Group B1 ）, and fiber - reinforced dowel - resin core with 2.0 mm ferrule （ Group B2 ）. Each specimen was embedded in a self - cured acrylic resin block from 2.0mm apical to the margins of a cast Ni - Cr alloy crown, and then loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0mm/min until fracture. Data were recorded and analyzed using ANOVA and Fisher＇s exact tests, with a = 0.05. Results Mean failure loads （kN） for groups A1, A2, B1, B2 were： 1.46 （S. D. 0.45）,1.07（0.21）,1.13（0.30）, 1.02（0.27）. Teeth restored with cast Ni- Cr dowel- cores and 2.0mm ferrules demonstrated marginally, significantly lower fracture strengths, PP = 0.04. There were significant differences between the two dowel systems in their fracture site patterns, P 〈 0.05. Conclusion Crown lengthening with a 2.0mm ferrule resulted in reduced fracture strengths for endodontically treated teeth restored using two dowel - core systems and cast metal crowns. The fiber - reinforced dowel - resin core system reduced the severity of the root fractures.