Department of Advanced Free Radical Science, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan.
Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, 980 8575, Japan.
J Mech Behav Biomed Mater. 2023 Oct;146:106067. doi: 10.1016/j.jmbbm.2023.106067. Epub 2023 Aug 4.
Monolithic dental prostheses made of 3-6 mol% yttria-stabilized zirconia (3-6YSZ) have gained popularity owing to their improved material properties and semi-automated fabrication processes. In this study, we aimed to evaluate the influence of mechanical surface treatments, such as polishing, grinding, and sandblasting, on the residual stress of 3-6YSZ used for monolithic prostheses in association with crystalline phase transformation. Plate specimens were prepared from five dental zirconia blocks: Aadva Zirconia ST (3YSZ), Aadva Zirconia NT (6YSZ), Katana HT (4YSZ), Katana STML (5YSZ), and Katana UTML (6YSZ). The specimens were either polished using 1, 3, or 9 μm diamond suspensions, ground using 15, 35, or 55 μm diamond discs, or sandblasted at 0.2, 0.3, or 0.4 MPa. The residual stress, crystalline phase, and hardness were analyzed using the cosα method, X-ray diffraction (XRD), and Vickers hardness test, respectively. Additionally, we analyzed the residual stress on the surfaces of monolithic zirconia crowns (MZCs) made of 4YSZ, 5YSZ, and 6YSZ, which were processed using clinically relevant procedures, including manual grinding, followed by polishing using a dental electric motor on the external surface, and sandblasting on the internal surface. Residual stress analysis demonstrated that grinding and sandblasting, particularly the latter, resulted in the generation of compressive residual stress on the surfaces of the plate specimens. XRD revealed that the ground and sandblasted specimens contained a larger amount of the rhombohedral phase than that of the polished specimens, which may be a cause of the residual stress. Sandblasting significantly increased the Vickers hardness compared to polishing, which may possibly be due to the generation of compressive residual stress. In the case of MZCs, compressive residual stress was detected not only on the sandblasted surface, but also on the polished surface. The difference in the residual stress between the plate and crown specimens may be related to the force applied during the automated and manual grinding and polishing procedures. Further studies are required to elucidate the effects of the compressive residual stress on the clinical performance of MZCs.
整体式牙科修复体由 3-6%氧化钇稳定氧化锆（3-6YSZ）制成，由于其材料性能得到改善和半自动化制造工艺，因此越来越受欢迎。本研究旨在评估机械表面处理（如抛光、研磨和喷砂）对整体式修复体用 3-6YSZ 残余应力的影响，同时研究其与晶体相转变的关系。从五个牙科氧化锆块制备板试件：Aadva Zirconia ST（3YSZ）、Aadva Zirconia NT（6YSZ）、Katana HT（4YSZ）、Katana STML（5YSZ）和 Katana UTML（6YSZ）。使用 1、3 或 9μm 的金刚石悬浮液对试件进行抛光，使用 15、35 或 55μm 的金刚石盘进行研磨，或在 0.2、0.3 或 0.4MPa 下喷砂。使用 cosα 法、X 射线衍射（XRD）和维氏硬度试验分别分析残余应力、晶体相和硬度。此外，我们还分析了由 4YSZ、5YSZ 和 6YSZ 制成的整体氧化锆冠（MZC）表面的残余应力，这些 MZC 是通过临床相关的程序加工而成的，包括手动研磨，然后在外部表面使用牙科电动工具抛光，内部表面喷砂。残余应力分析表明，研磨和喷砂，特别是后者，会在板试件表面产生压缩残余应力。XRD 表明，研磨和喷砂后的试件比抛光后的试件含有更多的四方相，这可能是残余应力的原因。与抛光相比，喷砂显著提高了维氏硬度，这可能是由于产生了压缩残余应力。对于 MZC，不仅在喷砂表面，而且在抛光表面都检测到压缩残余应力。板和冠试件之间残余应力的差异可能与自动化和手动研磨和抛光过程中施加的力有关。需要进一步的研究来阐明压缩残余应力对 MZC 临床性能的影响。
