To evaluate the influence of printing orientation on flexural strength (σf) and elastic modulus (E) of different 3D printing dental restorative resins. Bar-shaped specimens (n = 20) were fabricated from two SLA-printed resins (FT- Formlabs Temporary, and FP- Formlabs Permanent) and two DLP-printed resins (DFT- Detax Freeprint Temp, and GCT- GC Temporary) using two building orientations (0º and 90º). The 3D-printed structures were aged (14 d) before submitted to three-point bending in 37ºC distilled water at a crosshead speed of 1.0 ± 0.3 mm/min until fracture to calculate the σf and the E values. The fractured surfaces were evaluated using stereomicroscopy and scanning electron microscopy (SEM) following fractography principles. Data were statistically analyzed using two-way ANOVA and Tukey post-hoc (α = 0.001). FP and FT showed significantly higher E values than DFT and GCT, irrespectively of printing orientation (p < 0.001). There was no statistical difference between the building orientations (0º and 90º) for the mean σf and E values for the resin materials evaluated. Fractographic characteristics were similar for the surface fracture from all the materials evaluated, showing typical brittle fracture behavior. Printing orientation did not influence of flexural strength and elastic modulus values for the 3D-printed resin structures evaluated. Surface topography was mostly governed by the 3D printer type.

中文翻译：

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打印方向对老化 3D 打印修复树脂机械性能的影响

评估打印方向对不同3D打印牙科修复树脂的弯曲强度（σf）和弹性模量（E）的影响。条形样本 (n = 20) 由​​两种 SLA 打印树脂（FT-Formlabs Temporary 和 FP-Formlabs Permanent）和两种 DLP 打印树脂（DFT-Detax Freeprint Temp 和 GCT-GC Temporary）制成，使用两种材料建筑方向（0° 和 90°）。将 3D 打印结构老化（14 d），然后在 37°C 蒸馏水中以 1.0 ± 0.3 mm/min 的十字头速度进行三点弯曲，直至断裂，以计算 σf 和 E 值。根据断裂原理，使用立体显微镜和扫描电子显微镜（SEM）评估断裂表面。使用双向方差分析和 Tukey 事后分析对数据进行统计分析 (α = 0.001)。无论打印方向如何，FP 和 FT 的 E 值均显着高于 DFT 和 GCT (p < 0.001)。所评估的树脂材料的平均 σf 和 E 值在建筑方向（0° 和 90°）之间没有统计差异。所有评估材料的表面断裂断口特征相似，显示出典型的脆性断裂行为。打印方向不影响所评估的 3D 打印树脂结构的弯曲强度和弹性模量值。表面形貌主要由 3D 打印机类型决定。