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Abstract：
OBJECTIVE: To analyze the influence of forming direction on the surface characteristics, elastic modulus, bending strength and fracture toughness of printed parts and the relationship between forming direction and force direction, and to provide scientific basis and guidance for the clinical application of oral denture base resin materials.
METHODS: The 3D printing technology was used to print denture base resin samples. The shape and size of the samples referred to the current standard for testing conventional denture base materials. The samples used for physical performance testing were cylindrical (with a diameter of 15 mm and a thickness of 1 mm) and printed at different angles along the Z axis (0°, 45°, 90°). Scanning electron microscope was used to observe the microscopic topography of the different samples. The color stability of different samples was observed by color stabilizer. The surface roughness of the samples was analyzed by using surface roughness tester. The Vickers hardness was measured to analyze the hardness of the samples. The samples used for mechanical performance testing were rectangular (elastic modulus and bending strength: A length of 64 mm, a width of 10 mm, and a height of 3.3 mm; fracture toughness: A length of 39 mm, a width of 8 mm, and a height of 4 mm), divided into two groups: W group and H group. The W group was printed from the bottom up along the Z axis with the length × width as the bottom surface parallel to the X, Y axis plane, while the H group printed from the bottom up along the Z axis with the length × height as the bottom surface parallel to the X, Y axis plane. The forming angles of both groups were equally divided into 0°, 45°, and 90°. The elastic modulus, bending strength and fracture toughness of different samples were studied through universal mechanical testing machine. SPSS 22.0 software was used for statistical analysis.
RESULTS: The microscopic topography and roughness of different samples were closely related to the printing direction, with significant differences between the 0°, 45°, and 90° specimens. The 0° specimens had the smoothest surface (roughness < 1 μm). The surface of the 45° specimen was the roughest (roughness>3 μm). The microhardness of the 0° sample was the best [(196.13±0.20) MPa], with a significant difference compared with the 90° sample [(186.62±4.81) MPa, P < 0.05]. The mechanical properties of different samples were also closely related to the printing direction. The elastic modulus, bending strength, and fracture toughness of the 45° samples in the W group were the highest compared with the other groups. The results of elastic modulus showed that in the H group, the 45° specimens had the highest elastic mo-dulus, which was significantly different from the 0° and 90° specimens (P < 0.05). The elastic modulus of 0° and 45° specimens in the W group were higher than those in 90° specimens (P < 0.05). The bending strength results showed that there was no significant difference between the specimens from dif-ferent angles in the H group. The bending strength of the 90° specimens in the W group was the smallest, and there was a significant difference between 90° and the 0° and 45° specimens (P < 0.05); And the bendind strength of the 0° and 45° specimens in the W group was significantly higher than that of the 0° and 45° specimens in the H group (P < 0.05). The fracture toughness results showed that the fracture toughness of the H group specimens was lower than 1.9 MPa m1/2, which was specified in the denture base standard. The 45° samples in the W group were the highest, with significant differences compared with the 0° and 90° samples (P < 0.05). And the 90° samples of the W group specimens were lower than 1.9 MPa m1/2. And the fracture toughness of the 45° specimen in the W group was significantly higher than that of all the specimens in the H group (P < 0.05).
CONCLUSIONS: The 0° samples had relatively better physical properties. The 45° samples had the best mechanical properties. But the fracture toughness of specimens (H group and 90° samples of W group) did not yet meet clinical requirements. That indicated that the characteristics of the 3D printing denture base resin were affected by the printing direction. Only when the performance of the printed samples in all directions met the minimum requirements of the standard, they could be used in clinical practice.
METHODS: The 3D printing technology was used to print denture base resin samples. The shape and size of the samples referred to the current standard for testing conventional denture base materials. The samples used for physical performance testing were cylindrical (with a diameter of 15 mm and a thickness of 1 mm) and printed at different angles along the Z axis (0°, 45°, 90°). Scanning electron microscope was used to observe the microscopic topography of the different samples. The color stability of different samples was observed by color stabilizer. The surface roughness of the samples was analyzed by using surface roughness tester. The Vickers hardness was measured to analyze the hardness of the samples. The samples used for mechanical performance testing were rectangular (elastic modulus and bending strength: A length of 64 mm, a width of 10 mm, and a height of 3.3 mm; fracture toughness: A length of 39 mm, a width of 8 mm, and a height of 4 mm), divided into two groups: W group and H group. The W group was printed from the bottom up along the Z axis with the length × width as the bottom surface parallel to the X, Y axis plane, while the H group printed from the bottom up along the Z axis with the length × height as the bottom surface parallel to the X, Y axis plane. The forming angles of both groups were equally divided into 0°, 45°, and 90°. The elastic modulus, bending strength and fracture toughness of different samples were studied through universal mechanical testing machine. SPSS 22.0 software was used for statistical analysis.
RESULTS: The microscopic topography and roughness of different samples were closely related to the printing direction, with significant differences between the 0°, 45°, and 90° specimens. The 0° specimens had the smoothest surface (roughness < 1 μm). The surface of the 45° specimen was the roughest (roughness>3 μm). The microhardness of the 0° sample was the best [(196.13±0.20) MPa], with a significant difference compared with the 90° sample [(186.62±4.81) MPa, P < 0.05]. The mechanical properties of different samples were also closely related to the printing direction. The elastic modulus, bending strength, and fracture toughness of the 45° samples in the W group were the highest compared with the other groups. The results of elastic modulus showed that in the H group, the 45° specimens had the highest elastic mo-dulus, which was significantly different from the 0° and 90° specimens (P < 0.05). The elastic modulus of 0° and 45° specimens in the W group were higher than those in 90° specimens (P < 0.05). The bending strength results showed that there was no significant difference between the specimens from dif-ferent angles in the H group. The bending strength of the 90° specimens in the W group was the smallest, and there was a significant difference between 90° and the 0° and 45° specimens (P < 0.05); And the bendind strength of the 0° and 45° specimens in the W group was significantly higher than that of the 0° and 45° specimens in the H group (P < 0.05). The fracture toughness results showed that the fracture toughness of the H group specimens was lower than 1.9 MPa m1/2, which was specified in the denture base standard. The 45° samples in the W group were the highest, with significant differences compared with the 0° and 90° samples (P < 0.05). And the 90° samples of the W group specimens were lower than 1.9 MPa m1/2. And the fracture toughness of the 45° specimen in the W group was significantly higher than that of all the specimens in the H group (P < 0.05).
CONCLUSIONS: The 0° samples had relatively better physical properties. The 45° samples had the best mechanical properties. But the fracture toughness of specimens (H group and 90° samples of W group) did not yet meet clinical requirements. That indicated that the characteristics of the 3D printing denture base resin were affected by the printing direction. Only when the performance of the printed samples in all directions met the minimum requirements of the standard, they could be used in clinical practice.
摘要：
目的：分析成形方向对表面特性的影响，弹性模量,印刷零件的弯曲强度和断裂韧性以及成形方向与力方向之间的关系，为口腔义齿基托树脂材料的临床应用提供科学依据和指导。
方法：使用3D打印技术打印义齿基托树脂样品。样品的形状和尺寸参考用于测试常规义齿基托材料的当前标准。用于物理性能测试的样品为圆柱形（直径为15毫米，厚度为1毫米），并沿Z轴（0°，45°,90°)。使用扫描电子显微镜观察不同样品的微观形貌。通过颜色稳定剂观察不同样品的颜色稳定性。使用表面粗糙度测试仪分析样品的表面粗糙度。测量维氏硬度以分析样品的硬度。用于机械性能测试的样品为矩形（弹性模量和弯曲强度：长度为64mm，宽度为10毫米，高度为3.3毫米；断裂韧性：长度为39毫米，8毫米的宽度，和4毫米的高度），分为两组：W组和H组。W组沿Z轴从下到上打印，长度×宽度为底面平行于X，Y轴平面,而H组沿Z轴从下往上打印，长度×高度为平行于X的底面，Y轴平面。两组的成形角度均分为0°，45°,90°。弹性模量，通过万能力学试验机研究了不同试样的弯曲强度和断裂韧性。采用SPSS22.0软件进行统计分析。
结果：不同样品的微观形貌和粗糙度与印刷方向密切相关，0°之间存在显著差异，45°,和90°标本。0°试样具有最光滑的表面(粗糙度<1μm)。45°试样的表面是最粗糙的(粗糙度>3μm)。0°试样的显微硬度最好[(196.13±0.20)MPa],与90°样品[(186.62±4.81)MPa相比有显著差异，P<0.05]。不同样品的力学性能也与印刷方向密切相关。弹性模量，弯曲强度,与其他组相比，W组45°样品的断裂韧性最高。弹性模量测定结果表明,在H组中,45°试样的弹性最大,与0°和90°标本有显著差异(P<0.05)。W组0°和45°试样的弹性模量均高于90°试样(P<0.05)。弯曲强度结果表明，H组不同角度的试样之间没有显着差异。W组90°试样的抗弯强度最小,90°与0°和45°试样有显著性差异(P<0.05);W组0°和45°试样的弯曲强度明显高于H组0°和45°试样(P<0.05)。断裂韧性结果表明,H组试样的断裂韧性均低于义齿基托标准规定的1.9MPam1/2。W组45°样品最高,与0°和90°样品相比差异显著(P<0.05)。W组样品的90°样品低于1.9MPam1/2。W组45°试样的断裂韧性明显高于H组(P<0.05)。
结论:0°样品具有相对较好的物理性质。45°样品具有最好的机械性能。但试样(H组和W组90°试样)的断裂韧性尚未达到临床要求。这表明3D打印义齿基托树脂的特性受到打印方向的影响。只有当印刷样品在各个方向上的性能都满足标准的最低要求时，它们可以用于临床实践。
方法：使用3D打印技术打印义齿基托树脂样品。样品的形状和尺寸参考用于测试常规义齿基托材料的当前标准。用于物理性能测试的样品为圆柱形（直径为15毫米，厚度为1毫米），并沿Z轴（0°，45°,90°)。使用扫描电子显微镜观察不同样品的微观形貌。通过颜色稳定剂观察不同样品的颜色稳定性。使用表面粗糙度测试仪分析样品的表面粗糙度。测量维氏硬度以分析样品的硬度。用于机械性能测试的样品为矩形（弹性模量和弯曲强度：长度为64mm，宽度为10毫米，高度为3.3毫米；断裂韧性：长度为39毫米，8毫米的宽度，和4毫米的高度），分为两组：W组和H组。W组沿Z轴从下到上打印，长度×宽度为底面平行于X，Y轴平面,而H组沿Z轴从下往上打印，长度×高度为平行于X的底面，Y轴平面。两组的成形角度均分为0°，45°,90°。弹性模量，通过万能力学试验机研究了不同试样的弯曲强度和断裂韧性。采用SPSS22.0软件进行统计分析。
结果：不同样品的微观形貌和粗糙度与印刷方向密切相关，0°之间存在显著差异，45°,和90°标本。0°试样具有最光滑的表面(粗糙度<1μm)。45°试样的表面是最粗糙的(粗糙度>3μm)。0°试样的显微硬度最好[(196.13±0.20)MPa],与90°样品[(186.62±4.81)MPa相比有显著差异，P<0.05]。不同样品的力学性能也与印刷方向密切相关。弹性模量，弯曲强度,与其他组相比，W组45°样品的断裂韧性最高。弹性模量测定结果表明,在H组中,45°试样的弹性最大,与0°和90°标本有显著差异(P<0.05)。W组0°和45°试样的弹性模量均高于90°试样(P<0.05)。弯曲强度结果表明，H组不同角度的试样之间没有显着差异。W组90°试样的抗弯强度最小,90°与0°和45°试样有显著性差异(P<0.05);W组0°和45°试样的弯曲强度明显高于H组0°和45°试样(P<0.05)。断裂韧性结果表明,H组试样的断裂韧性均低于义齿基托标准规定的1.9MPam1/2。W组45°样品最高,与0°和90°样品相比差异显著(P<0.05)。W组样品的90°样品低于1.9MPam1/2。W组45°试样的断裂韧性明显高于H组(P<0.05)。
结论:0°样品具有相对较好的物理性质。45°样品具有最好的机械性能。但试样(H组和W组90°试样)的断裂韧性尚未达到临床要求。这表明3D打印义齿基托树脂的特性受到打印方向的影响。只有当印刷样品在各个方向上的性能都满足标准的最低要求时，它们可以用于临床实践。
