Oper Dent. 2019 Jul/Aug;44(4):E190-E201. doi: 10.2341/18-161-L. Epub 2019 Mar 8.
To evaluate and compare the fracture toughness of dental CAD/CAM materials of different material classes intended for in-office milling (glass ceramics, hybrid, resin composites) and the influence of aging on this property.
The fracture toughness (critical intensity factor, K) values of 9 CAD/CAM restorative materials (Ambarino High-Class, Brilliant Crios, Cerasmart, exp. CAD/CAM composite, Katana Avencia, Lava Ultimate, VITA Enamic, IPS Empress CAD, and IPS e.max CAD) were determined using the SEVNB method in a four-point bending setup. Twenty bending bars of each material with a 4 × 3 cross and a minimum length of 12 mm were cut out of CAD/CAM milling blocks. Notching was done starting with a pre-cut and consecutive polishing and v-shaping with a razor blade, resulting in a final depth of v-shaped notches of between 0.8 and 1.2 mm. Half of the specimens were selected for initial fracture toughness measurements. The others were thermocycled in distilled water for 30,000× (5/55°C; 30-second dwell time) before testing. Specimen fracture surfaces were analyzed using confocal laser scanning microscopy.
All specimens for each material fractured into two fragments and showed the typical compression curl and brittle failure markings. Comparing initial K values, lithium disilicate ceramic IPS e.max CAD showed significantly the highest and leucite-reinforced ceramic IPS Empress CAD significantly the lowest K values (<0.001). All tested CAD/CAM materials with a resin component ranged in the same K value group (>0.999-0.060). After thermal cycling, the highest K values were measured for lithium disilicate ceramic IPS e.max CAD, followed by resin composite materials Ambarino High-Class (<0.001-0.006) and hybrid material VITA Enamic (<0.001-0.016), while the significantly lowest values were reflected for the resin composite materials Cerasmart, LAVA Ultimate (<0.001-0.006), and Katana Avencia (<0.001-0.009). The roughness of the fracture surfaces varied depending on the microstructure of the respective material. The ceramic surfaces showed the smoothest surfaces. The fracture surface of VITA Enamic revealed microstructural inhomogeneities and microcracks. For CAD/CAM resin composite materials, crack paths through the matrix and interfaces of matrix and fillers could be observed at the microstructure level.
The materials tested show differences in fracture toughness typical for the class they belong to. With one exception (Ambarino High-Class), thermocycling affected the fracture toughness of materials with a resin component negatively, whereas the leucite and lithium disilicate ceramic showed stability.
评估和比较不同材料类别（玻璃陶瓷、混合体、树脂复合材料）的牙科 CAD/CAM 材料的断裂韧性，并研究老化对该性能的影响。
采用四点弯曲试验装置中的 SEVNB 法测定 9 种 CAD/CAM 修复材料（Ambarino High-Class、Brilliant Crios、Cerasmart、exp.CAD/CAM 复合材料、Katana Avencia、Lava Ultimate、VITA Enamic、IPS Empress CAD 和 IPS e.max CAD）的断裂韧性（临界强度因子，K）值。从 CAD/CAM 铣削块中切割出每种材料的 20 个具有 4×3 交叉和最小长度为 12mm 的弯曲棒。通过预切割和连续抛光以及使用剃须刀片进行 V 形加工来进行开槽，最终 V 形切口的深度在 0.8 至 1.2mm 之间。一半的样品用于初始断裂韧性测量。其余样品在蒸馏水中进行 30,000×（5/55°C；30 秒停留时间）热循环，然后进行测试。使用共焦激光扫描显微镜分析样品的断裂表面。
每种材料的所有样品均断裂成两个碎片，并显示出典型的压缩卷曲和脆性失效标记。比较初始 K 值，二硅酸锂陶瓷 IPS e.max CAD 的 K 值最高，而透锂长石增强陶瓷 IPS Empress CAD 的 K 值最低（<0.001）。所有具有树脂成分的测试 CAD/CAM 材料的 K 值均处于同一组（>0.999-0.060）。热循环后，二硅酸锂陶瓷 IPS e.max CAD 的 K 值最高，其次是树脂复合材料 Ambarino High-Class（<0.001-0.006）和混合材料 VITA Enamic（<0.001-0.016），而树脂复合材料 Cerasmart、LAVA Ultimate（<0.001-0.006）和 Katana Avencia（<0.001-0.009）的 K 值明显最低。断裂表面的粗糙度取决于各自材料的微观结构。陶瓷表面显示出最光滑的表面。VITA Enamic 的断裂表面显示出微观结构不均匀和微裂纹。对于 CAD/CAM 树脂复合材料，可以在微观结构水平上观察到穿过基质和基质与填料界面的裂纹路径。
测试的材料在断裂韧性方面表现出与其所属类别典型的差异。除了一种例外（Ambarino High-Class），热循环对具有树脂成分的材料的断裂韧性产生负面影响，而透锂长石和二硅酸锂陶瓷则表现出稳定性。
