Neoh Siew Peng, Khantachawana Anak, Santiwong Peerapong, Chintavalakorn Rochaya, Srikhirin Toemsak
Department of Orthodontics, Faculty of Dentistry, Mahidol University, 6 Yothi Alley, Phayathai, Bangkok, 10400, Thailand.
Department of Mechanical Engineering, Faculty of Engineering, King Mongkut's University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mot, Thung Khru, Bangkok, 10140, Thailand.
Clin Oral Investig. 2025 Jan 6;29(1):48. doi: 10.1007/s00784-024-06120-4.
To address the high surface roughness and poor optical properties of three-dimensional (3D) printed orthodontic clear retainers, an alternative post-processing protocol was investigated with the goal of achieving improved surface, optical, and mechanical properties while preserving dimensional accuracy.
Samples were prepared from two biocompatible methacrylate-based 3D-printing resins (Formlabs Dental LT Clear V2, NextDent OrthoFlex) and one thermoplastic material (Duran). For the 3D-printed resins, one group was post-processed by rinsing in isopropyl alcohol, while another group was centrifuged before post-curing in glycerine. Three different testing conditions were used: dry, wet (24-h water immersion), and aged (thermocycling for 10,000 cycles). Surface characteristics were evaluated qualitatively and quantitatively. Optical properties were assessed for transparency and colour stability, while mechanical properties were elicited from tensile and microhardness tests. Water sorption and solubility were calculated. Samples mounted on a dental model were scanned by micro-computed tomography to measure thickness and gap width.
3D-printed samples post-processed by centrifugation showed significantly decreased surface roughness and improved visible light transmission, colour stability, tensile strength, and hardness. The centrifuged samples showed significantly increased thickness, while designing an offset equal to this thickness improved the adaptation.
Post-processing by centrifugation produces surface coating that enhances the surface and optical properties of the 3D-printed orthodontic retainers, while curing in an oxygen-free environment improves their mechanical properties. Design modifications may be necessary for this protocol to ensure proper adaptation to the dentition.
Proper design and post-processing protocols are necessary to achieve the desired properties of orthodontic clear retainers.
为解决三维（3D）打印正畸透明保持器表面粗糙度高和光学性能差的问题，研究了一种替代后处理方案，目标是在保持尺寸精度的同时改善表面、光学和机械性能。
从两种生物相容性甲基丙烯酸酯基3D打印树脂（Formlabs Dental LT Clear V2、NextDent OrthoFlex）和一种热塑性材料（Duran）制备样品。对于3D打印树脂，一组通过在异丙醇中冲洗进行后处理，而另一组在甘油中后固化前进行离心处理。使用三种不同的测试条件：干燥、潮湿（24小时水浸）和老化（热循环10000次）。对表面特征进行定性和定量评估。评估光学性能的透明度和颜色稳定性，同时通过拉伸和显微硬度测试得出机械性能。计算吸水率和溶解度。通过微型计算机断层扫描对安装在牙科模型上的样品进行扫描，以测量厚度和间隙宽度。
经离心后处理的3D打印样品表面粗糙度显著降低，可见光透射率、颜色稳定性、拉伸强度和硬度得到改善。离心后的样品厚度显著增加，设计一个等于该厚度的偏移量可改善贴合度。
离心后处理产生表面涂层，可增强3D打印正畸保持器的表面和光学性能，而在无氧环境中固化可改善其机械性能。可能需要对该方案进行设计修改，以确保与牙列的正确贴合。
正确的设计和后处理方案对于实现正畸透明保持器的理想性能是必要的。
