不同形态牙本质肩领与牙根抗力的实验研究

目的:研究5种不同形态牙本质肩领对牙根抗力的影响。方法:25颗完整离体上颌中切牙随机分成5组,按实验设计制备5种不同形态牙本质肩领:即360°环形肩领组、180°唇侧肩领组、180°腭侧肩领组、180°远中肩领组和无肩领组。所有离体牙均采用预成石英纤维桩、复合树脂核、镍铬合金全冠修复。试件于铸造全冠颈缘线下2mm包埋在自凝塑料中,电子万能试验机以与牙长轴成130°,加载速度为1.0mm/min,于样本牙腭面切端下2mm处加载,记录折裂载荷及牙体断裂的位置和方式,进行统计学分析。结果:5组样本牙抗折力值顺序为环形肩领组、腭侧肩领组远中肩领组唇侧肩领组无肩领组,前两组样本牙根抗折力显著高于后两组,差异有显著性(P0.01)。所有样本中可修复性折裂占92%。结论:残根龈上剩余牙本质的位置能影响桩核冠修复后的牙根抗力。

Effect of different forms of dentine shoulder collar on root resistance

Objective To study the effect of 5 different forms of dentine shoulder collar on root resistance.Methods 25 extracted intact maxillary human central incisors were randomly assigned to 1 of 5 groups：360° circular shoulder collar group,180° labial shoulder collar group,180° palatal shoulder collar group,180° distal shoulder collar group and no shoulder collar group.All the prepared teeth were restored with quartz fiber posts,resin composite core,and nickel-chromium alloy crowns.All the prepared teeth were embedded in the self curing plastic along 2mm under the casting crowns cervical margin line.The electronic universal testing machine was used to record the fracture loads and the mode of fracture with the long axis of the tooth of 130 °,the loading rate of 1.0mm/min at 2mm under the palatal incisal margin.Statistical analysis was performed with 1-way analysis of Variance （ANOVA）.Results The sequence of root resistance value is circular collar group and palatal collar group＞distal collar group＞labial collar group＞no collar group.The root bending stress of the first two groups was significantly higher than that of the latter two groups （P＜O.01）.Of all the samples,the repairable fracture accounted for 92％.Conclusion The supragingival dentin position of residual root can influence the post core crown restoration.