Fracture Prevention of Esthetic Ceramic Crowns for Posterior Teeth

1. 美观陶瓷材料的疲劳试验：用于评估试验的样品（20×5×1.5 mm）由OCC制成，其表面抛光至#220和#1000。采用伺服液压机械试验机进行强度测试。#220组试件的抗弯强度、疲劳强度和断裂次数平均值分别为40.9 MPa、28.8 MPa和4.31×10^4次，#1000组试件的抗弯强度、疲劳强度和断裂次数平均值分别为45.4 MPa、35.0 MPa和3.29×10^4次。这些结果表明，与树脂复合材料相比，OCC是不易破碎的材料，其表面抛光是获得更高强度的必要条件。美学陶瓷材料与牙科合金或复合材料复合材料的疲劳试验：用胶粘剂树脂水泥将OCC与银钯铜金合金或复合材料（厚度为2mm）连接在一起进行疲劳试验。#220组的抗折强度和抗疲劳强度平均值为49.6 MPa和39.3 MPa， #1000组的抗折强度平均值为54.7 MPa和44.3 MPa。另一方面，OCC和复合材料组合用于堆芯的强度分别为220组76.3 MPa和65.5 MPa， 1000组74.8 MPa和62.2 MPa。结果表明，与单一OCC材料相比，两种配合物的强度均有提高，且OCC材料的表面抛光不影响两种配合物的强度。三种基牙的OCC冠胶结耐久性试验：采用人牙、金属或复合材料制备三种基牙，其平咬合面高度为2mm，深槽缘宽度为1mm。在三个基牙上分别用粘接树脂水泥粘接OCC冠，然后用5kgf将冠加载到咬合面上的骨折上，进行10万次循环。OCC冠对人牙、金属和复合材料的断裂载荷分别为107 kgf、192 kgf和160 kgf。OCC冠对人牙的断裂载荷明显低于其他两个基牙的断裂载荷。少

1. Fatigue tests of esthetic ceramic material : Specimens (20×5×1.5 mm) for evaluated tests were prepared by made of the OCC and their surfaces were polished to #220 and #1000. The strengths were measured with a servohydraulic mechanical testing machine. The averages of flexural strength, fatigue strength, and the number of cycles when specimens fractured were 40.9 MPa, 28.8 MPa, and 4.31×10^4 cycles for the #220-group and 45.4 MPa, 35.0 MPa, and 3.29×10^4 cycles for the #1000-group, respectively. These results suggested that the OCC was not breakable material compared with resin composite and that its surface polishing was essential to obtain greater strengths.2. Fatigue tests of the complexes of esthetic ceramic material and dental alloy or composite for core build-up : Specimens joined between the OCC and silver-palladium-copper-gold alloy or composite for core build-up (2 mm in thickness) with adhesive resin cement were prepared for fatigue tests. The averages of flexural strength … More and fatigue strength with the combination of the OCC and alloy were 49.6 MPa and 39.3 MPa for the #220-group and 54.7 MPa and 44.3 MPa for the #1000-group, respectively. On the other hand, their strengths with the combination of the OCC and composite for core build-up were 76.3 MPa and 65.5 MPa for the #220-group and 74.8 MPa and 62.2 MPa for the #1000-group, respectively. These results showed that the strengths of both complexes were improved compared with the single OCC material and that the surface polishing of the OCC material did not influenced both strengths.3. Durability tests of the cemented OCC crown on each of the three abutments : Three types of abutments were prepared with flat occlusal surface of 2 mm in height and deep-chamfer margin of 1 mm in width by use of human tooth, metal, or composite for core build-up. The OCC crowns were luted with adhesive resin cement on each of the three abutments, followed by loading crown to the fracture on the occlusal surface with 5 kgf for 100,000 cycles. The observed fractured loads of OCC crowns on human tooth, metal, and composite were 107 kgf, 192 kgf, and 160 kgf, respectively. The fractured load of the OCC crown on human tooth showed significantly lower value than that of crowns on the other two abutments. Less