成型方向对3D打印口腔义齿基托树脂材料物理性能及力学性能的影响

Effect of printing orientation on physical and mechanical properties of 3D printing prosthodontic base resin materials

目的:分析成型方向对打印件的表面特征、弹性模量、挠曲强度及断裂韧性的影响及其与受力方向之间的关系,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:采用3D打印技术使用义齿基托树脂材料打印义齿基托树脂试样,试样形状及尺寸参考目前常规义齿基托材料检测标准。检测物理性能的试样为圆柱体(直径15 mm、厚1 mm),在Z轴的不同角度方向上(0°、45°、90°)进行打印。扫描电镜观察经不同方向打印后试样的表面微观形貌;试样经色稳定仪浸水光照后观察其颜色稳定性;利用粗糙度仪分析试样表面粗糙程度;用维氏硬度计测量硬度。检测力学性能的试样为长方体(检测弹性模量和挠曲强度:长64 mm、宽10 mm、高3.3 mm;检测断裂韧性:长39 mm、高8.0 mm、宽4.0 mm),分为W、H两组,W组以长×宽为底面,平行X、Y轴平面,自下而上沿Z轴开始打印,H组以长×高为底面,平行X、Y轴平面,自下而上沿Z轴开始打印,两组成型角度均分为0°、45°和90°,通过万能力学试验机研究其弹性模量、挠曲强度和断裂韧性。采用SPSS 22.0软件对数据进行统计分析。结果:表面形貌和粗糙度与成型方向密切相关,0°、45°及90°试样之间差异具有统计学意义,0°试样表面最光滑(粗糙度<1μm),45°试样表面最粗糙(粗糙度>3μm)。0°试样硬度最佳[(196.13±0.20)MPa],与90°试样[(186.62±4.81)MPa]比较差异具有统计学意义(P<0.05)。试样的力学性能与打印方向也密切相关,W组45°试样的弹性模量、挠曲强度及断裂韧性与其他方向试样比较均为最高,差异具有统计学意义。弹性模量结果显示,H组中,45°试样弹性模量最高,与0°和90°试样比较差异具有统计学意义(P<0.05);W组中0°及45°试样高于90°试样(P<0.05);且W组0°及45°试样的弹性模量均显著高于H组0°及45°试样(P<0.05)。挠曲强度结果显示,H组各角度试样之间差异无统计学意义,W组中90°试样强度最小,与0°及45°试样之间比较差异具有统计学意义(P<0.05),且W组0°及45°试样的强度均显著高于H组0°及45°试样(P<0.05)。断裂韧性结果显示,H组各角度试样断裂韧性均低于义齿基托材料检测标准规定的1.9 MPa m1/2;W组45°试样最高,与0°及90°试样比较差异具有统计学意义(P<0.05),90°试样断裂韧性低于1.9 MPa m1/2。结论:成型方向为0°的试样在物理性能上相对较优,而45°试样具有最优的力学性能;以长×高为底面沿Z轴不同方向打印的试样(H组)以及以长×宽为底面沿Z轴90°打印的试样(W组90°)的断裂韧性尚不满足临床要求,提示3D打印义齿基托树脂性能受打印方向影响,只有各个方向打印试样的各项性能均满足义齿基托材料检测标准的最低要求,才可用于临床。

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<1μm).The surface of the 45°specimen was the roughest(roughness>3μm).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 m 1/2,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 m 1/2.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).Conclusion: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.