不同桩核材质和牙本质肩领包绕度对残根抗折力影响的实验研究

Effect of ferrule wrapping on fracture resistance of endodontically treated mandibular premolars restored with two different post-and-core materials

目的比较研究不同桩核材质和不同牙本质肩领包绕度对残根抗折强度的影响。方法32颗完整离体下颌第一前磨牙经完善根管治疗后,于舌侧釉牙骨质界上2.0mm处截冠,残留冠根长(15.0±1.0)mm。所有牙根随机分为4组,A1、B1组为2.0mm完整牙本质肩领预备组;A2、B2组为颊侧0.0mm、舌侧2.0mm的半包绕肩领组;A1、A2组为铸造桩核修复,B1、B2组为预成纤维桩核修复。铸造全冠粘固修复后,所有试件自全冠颈缘完成线根方2.0 mm包埋于自凝塑料块中。将试件以与牙长轴成135°放置于万能试验机上进行力学加载,直至试件折裂。记录试件断裂载荷并进行统计学分析(P=0.05)。结果A1、A2、B1、B2四组试件的断裂载荷均值(kN)依次为:1.33±0.19、0.73±0.09、1.04±0.15、1.01±0.21。"肩领包绕度"可显著影响修复后牙体的折裂强度(F=29.188,P=0.000),而"桩核材料"的影响无统计学意义(F=0.047,P=0.829)。桩核材料对试件的破损模式亦有显著的影响(P<0.05)。结论铸造桩核修复下颌第一前磨牙残根时,在残根颈部预备高2.0mm全包绕肩领,与舌侧半包绕肩领相比,可显著提高残根的抗折强度;而预成纤维桩核修复时,残根颈部肩领的完整与否以及设计位置对残根抗折强度的影响甚微。

Objective To evaluate the effect of different post core materials and different ferrule designs on the fracture resistance of endodontically treated mandibular premolars.Methods Thirty-two extracted mandibular first premolars were each sectioned perpendicular to the long axis at a point 2.0 mm occlusal to the buccal cementoenamel junction,with the residual root length(15±1.0)mm.All the roots were randomly divided into four groups.Groups A1 and B1 were given 2 mm complete ferrule design;and Groups A2 and B2 were given the incomplete ferrule preparation,with0.0 mm in buccal surface and 2.0 mm height in lingual surface.Roots in groups A1 and A2 were restored with cast dowel system,and those in group B1 and B2 were restored with prefabricated fiber post and core system.After restoration with a cast Co-Cr alloy crown,each specimen was embedded in an acrylic resin block to a height on the root 2.0 mm from the apical surface of the crown margin and loaded to fracture at a 135°angle to its long axis in a universal testing machine.Data were analyzed statistically using two-way ANOVA with Tukey HSD tests and Fisher’s test,withα=0.05.Results Mean failure loads(kN)for A1,A2,B1,B2 Groups were:1.33(S.D.0.19),0.73(0.09),1.04(0.15),1.01(0.21).Two-way ANOVA revealed significant differences for the effect of ferrule lengths(P=0.000)but no differences for the effect of cervical treatment methods(P=0.829).The dowel materials still significantly affected the fracture modes of the specimens in four groups(P<0.05).Conclusion When restored with cast dowel restoration,a 2.0 mm complete ferrule could significantly increase the fracture resistance of endodontically treated mandibular first premolar.However,if restored with prefabricated fiber post and core system,the effect of ferrule wrapping and the location of ferrule preparation showed no differences on the fracture resistance of endodontically treated roots.