悬臂梁实验评价玻璃纤维增强树脂桩材料的挠曲特性

Bending properties of glass fiber-reinforced plastic for post materials evaluated by cantilever test

背景:玻璃纤维增强树脂桩替代传统的金属桩已越来越多被应用于牙体缺损的修复治疗,但其形状特殊、尺寸较小,使用传统的弯曲实验很难准确评价其机械性能。目的:利用悬臂梁实验对3种市售玻璃纤维增强树脂桩(GFP,FBK和EVS)的挠曲特性进行评价。方法:根据玻璃纤维增强树脂桩的直径范围(0.9～1.0mm,1.2～1.25mm,1.4～1.5mm和1.6mm)将其分为4组。将每根玻璃纤维增强树脂桩一端包埋于树脂水门汀后作为测试样本,借助夹具固定于物性测试仪上,以6mm/min加载速率完成悬臂梁测试。结果与结论:典型的载荷-挠度曲线可见3种玻璃纤维增强树脂桩在超过比例限发生折断之前均伴有数次显著的载荷下降。实验将首次载荷下降前的峰值(称为pop-in载荷)作为玻璃纤维增强树脂桩的一个重要机械性能参数进行了测量。在pop-in载荷后的玻璃纤维增强树脂桩表面扫描电镜照片中可见呈剥离状态的玻璃纤维及沿纤维走行方向产生的裂隙。虽然最大载荷值随玻璃纤维增强树脂桩直径的增加而增大,但挠曲强度值却呈现减小趋势。GFP和FBK桩的弹性模量值随桩直径的增大而明显减小,直径1.0mmFBK桩的挠曲强度和弹性模量值最高。结果表明悬臂梁实验可以在模拟临床条件下用于评价玻璃纤维增强树脂桩的挠曲性能;pop-in载荷值是评价玻璃纤维增强树脂桩临床预后的有用指标。

BACKGROUND：Glass fiber reinforced plastic（GFRP） has been introduced as an alternative root canal post material for conventional metal castand prefabricated posts,but the unique shape and small sizes of the commercial GFRP posts has made the mechanical evaluations difficult using conventional bending tests.OBJECTIVE：To evaluate the bending properties of three types of commercial GFRP posts using a sensitive cantilever test.METHODS：Three commercial GFRP posts with different diameters were used in this study,and tested posts were divided into four groups based on diameter ranges（0.9-1.0 mm,1.2-1.25 mm,1.4-1.5 mm and 1.6 mm）.Bending specimens were prepared by embedding half of each post into resin cement in a mould,and then fixed into the jig and subjected to a cantilever test in a texture analyzer with a load speed of 6 mm/min.RESULTS AND CONCLUSION：Typical load-deflection curves of the GFRP posts included a number of sharp decreases of load after the proportional limits and before fractures.The peak load before the first decrease of load was defined as a pop-in load,and used as an index of an important mechanical property.Debending of the fibers from the matrix and crack initiation after the pop-in load appeared in scanning electron microscopy photomicrographs of the GFRP post surfaces.The maximum bending load tended to increase with an increase of post diameter;however,the bending strength decreased with an increase in diameter.The elastic modulus of GFP and FBK posts decreased significantly with an increase of post diameter.The bending strength and elastic moduli of FBK posts with a diameter of 1.0 mm were the highest among the tested posts.The bending properties of GFRP posts may be evaluated under clinical situation using a sensitive cantilever test.The behavior of pop-in load was a useful index of evaluation of clinical prognoses of GFRP posts.