title: Surface quality of yttria-stabilized tetragonal zirconia polycrystal in CAD/CAM milling, sintering, polishing and sandblasting processes.
abstract: This paper studied the surface quality (damage, morphology, and phase transformation) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in CAD/CAM milling, and subsequent polishing, sintering and sandblasting processes applied in dental restorations. X-ray diffraction and scanning electron microscopy (SEM) were used to scan all processed surfaces to determine phase transformations and analyse surface damage morphology, respectively. The average surface roughness (Ra) and maximum roughness (Rz) for all processed surfaces were measured using desk-top SEM-assisted morphology analytical software. X-ray diffraction patterns prove the sintering-induced monoclinic-tetragonal phase transformation while the sandblasting-induced phase transformation was not detected. The CAD/CAM milling of pre-sintered Y-TZP produced very rough surfaces with extensive fractures and cracks. Simply polishing or sintering of milled pre-sintered surfaces did not significantly improve their surface roughness (ANOVA, p>0.05). Neither sintering-polishing of the milled surfaces could effectively improve the surface roughness (ANOVA, p>0.05). The best surface morphology was produced in the milling-polishing-sintering process, achieving Ra=0.21±0.03µm and Rz=1.73±0.04µm, which meets the threshold for bacterial retention. Sandblasting of intaglios with smaller abrasives was recommended as larger abrasive produced visible surface defects. This study provides technical insights into process selection for Y-TZP to achieve the improved restorative quality.
authors: Mechanical Engineering, College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia.
authors: Abdur-Rasheed
authors: AR
authors: Alao
authors: Restorative Dentistry, College of Medicine and Dentistry, James Cook University, Cairns, QLD 4870, Australia.
authors: Richard
authors: R
authors: Stoll
authors: Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Mechanical Engineering, Tianjin University, Tianjin 300072, China.
authors: Xiao-Fei
authors: XF
authors: Song
authors: Division of Biomaterials and Engineering, Department of Conservative Dentistry, Showa University School of Dentistry, Tokyo 142-8555, Japan.
authors: Takashi
authors: T
authors: Miyazaki
authors: Division of Biomaterials and Engineering, Department of Conservative Dentistry, Showa University School of Dentistry, Tokyo 142-8555, Japan.
authors: Yasuhiro
authors: Y
authors: Hotta
authors: Division of Biomaterials and Engineering, Department of Conservative Dentistry, Showa University School of Dentistry, Tokyo 142-8555, Japan.
authors: Yo
authors: Y
authors: Shibata
authors: Mechanical Engineering, College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia. Electronic address: ling.yin@jcu.edu.au.
authors: Ling
authors: L
authors: Yin
mesh_terms: D017266:Dental Prosthesis; D008422:Materials Testing; D013499:Surface Properties; D015019:Yttrium / Q000032:analysis*; D015040:Zirconium / Q000032:analysis*
chemical_list: D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide; C091417:yttria
keywords: CAD/CAM milling; Material removal mechanisms; Phase transformation; Surface damage & morphology; Surface treatments; Yttria-stabilized tetragonal zirconia polycrystal