PhD Candidate, Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Affiliate Assistant Professor, Graduate Prosthodontics, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash and Faculty and Director of Research and Digital Dentistry, Kois Center, Seattle, Wash; Adjunct Professor, Department of Prosthodontics, School of Dental Medicine, Tufts University, Boston, Mass; Researcher at Revilla Research Center, Madrid, Spain.
J Prosthet Dent. 2023 May;129(5):788-795. doi: 10.1016/j.prosdent.2021.08.010. Epub 2021 Oct 1.
Additive manufacturing (AM) is a technology that has been recently introduced into dentistry for fabricating dental devices, including interim restorations. Printing orientation is one of the important and influential factors in AM that affects the accuracy, surface roughness, and mechanical characteristics of printed objects. However, the optimal print orientation for best bond strength to 3D-printed interim restorations remains unclear.
The purpose of this in vitro study was to evaluate the effect of printing orientation on the surface roughness, topography, and shear bond strength of AM interim restorations to composite resin.
Disk-shaped specimens (Ø20×10 mm) were designed by a computer-aided design software program (Geomagic freeform), and a standard tessellation language (STL) file was obtained. The STL file was used for the AM of 60 disks in 3 different printing orientations (0, 45, and 90 degrees) by using E-Dent 400 C&B material. An autopolymerizing interim material (Protemp 4) was used as a control group (CNT), and specimens were fabricated by using the injecting mold technique (n=20). Surface roughness (Sa, Sz parameters) was measured by using a 3D-laser scanning confocal microscope (CLSM) at ×20 magnification. For shear bond testing, the specimens were embedded in polymethylmethacrylate autopolymerized resin (n=20). A flowable composite resin was bonded by using an adhesive system. The specimens were stored in distilled water at 37 °C for 1 day and thermocycled 5000 times. The shear bond strength (SBS) was measured at a crosshead speed of 1 mm/min. The data were analyzed by 1-way ANOVA, followed by the Tukey HSD test (α=.05).
The 45-degree angulation printing group reported the highest Sa, followed by the CNT and the 90-degree and 0-degree angulations with significant difference between them (P<.001). The CNT showed the highest Sz, followed by the 45-degree, 90-degree, and 0-degree angulations. The mean ±standard deviation SBS was 28.73 ±5.82 MPa for the 90-degree, 28.21 ±10.69 MPa for the 45-degree, 26.21 ±11.19 MPa for the 0-degree angulations and 25.39 ±4.67 MPa for the CNT. However, no statistically significant difference was found in the SBS among the groups (P=.475).
Printing orientation significantly impacted the surface roughness of 3D-printed resin for interim restorations. However, printing orientation did not significantly affect the bond strength with composite resin.
增材制造（AM）是一种最近引入牙科领域用于制造牙科设备的技术，包括临时修复体。打印方向是 AM 中一个重要且有影响力的因素，它会影响打印物体的精度、表面粗糙度和机械特性。然而，用于获得与 3D 打印临时修复体最佳结合强度的最佳打印方向尚不清楚。
本体外研究的目的是评估打印方向对 AM 临时修复体与复合树脂的表面粗糙度、形貌和剪切结合强度的影响。
通过计算机辅助设计软件程序（Geomagic freeform）设计圆盘形试件（Ø20×10mm），并获得标准曲面语言（STL）文件。使用 E-Dent 400 C&B 材料，通过增材制造（AM）在 3 个不同的打印方向（0、45 和 90 度）制造 60 个圆盘的标准 tessellation language（STL）文件。使用自聚物临时材料（Protemp 4）作为对照组（CNT），并通过注塑模技术制造试件（n=20）。使用三维激光共聚焦显微镜（CLSM）在×20 放大倍数下测量表面粗糙度（Sa、Sz 参数）。用于剪切结合测试，将样本嵌入甲基丙烯酸甲酯自聚物树脂中（n=20）。使用粘接系统将可流动复合树脂粘结。将样本在 37°C 的蒸馏水中储存 1 天，并进行 5000 次热循环。以 1mm/min 的十字头速度测量剪切结合强度（SBS）。使用单向方差分析（ANOVA）分析数据，然后使用 Tukey HSD 检验（α=.05）。
45 度角打印组报告的 Sa 值最高，其次是 CNT 组和 90 度组和 0 度组，它们之间有显著差异（P<.001）。CNT 组的 Sz 值最高，其次是 45 度、90 度和 0 度组。90 度角的平均±标准偏差 SBS 为 28.73±5.82MPa，45 度角的平均±标准偏差 SBS 为 28.21±10.69MPa，0 度角的平均±标准偏差 SBS 为 26.21±11.19MPa，CNT 的平均±标准偏差 SBS 为 25.39±4.67MPa。然而，各组之间的 SBS 无统计学差异（P=.475）。
打印方向显著影响 3D 打印临时修复体的树脂表面粗糙度。然而，打印方向对与复合树脂的结合强度没有显著影响。
