title: Effect of polishing instruments and polishing regimens on surface topography and phase transformation of monolithic zirconia: An evaluation with XPS and XRD analysis.
abstract: Polishing procedures might alter monolithic zirconia (MZ) surface resulting in phase changes that can be deleterious for clinical performance and antagonist tooth wear. This study investigated the topographical features and phase transformation in MZ after polishing with different regimens simulating the clinical workflow. ​
  
  
  
  MZ specimens (Katana Zirconia HT, Kuraray-Noritake) (12×12×1.8 mm(3)) were grinded and polished using one of the five systems assessed: BG: Silicone carbide polishers (Brownie, Greenie, Super Greenie); CG: Diamond impregnated ceramic polisher kit (Ceragloss); EV: Synthetically bonded grinder interspersed with diamond (EVE Kit); SL: Urethane coated paper with aluminium oxide grits (Soflex Finishing and Polishing System Kit) and DB: Diamond bur (8 µm). Polished specimens were initially roughened with 220 µm diamond burs (Grinding Bur-GB) (10 s, 160.000160,000 rpm) and considered for baseline measurements. Polishing regimens were performed for 10 s using a slow-speed hand piece under water-cooling except for SL, in a custom made device (750 g; 5000 and 75,000 rpm). Surface roughnesses, phase changes (XRD) were assessed, surface characterization was performed (SEM, EDS).
  
  
  
  The highest roughness was obtained with the EV system (1.11 µm) compared to those of other systems (0.13-0.4 µm) (pθ and minor peak at 34.94°2θ. While GB, CG, EV, SL and DB exhibited a peak shift to the left, BG demonstrated a right peak shift on the 2θ scale. Monoclinic phase change was not noted in any of the groups.
  
  
  
  All polishing methods, except BG, exhibited a peak shift towards the lower angles of the 2-theta scale. Since the peak shifts were in the order of fractions of an angle they are attributed to stress formation rather than a phase change in the material. Thus, all polishing systems tested may not be detrimental for the phase transformation of MZ. EV system resulted in the highest roughness and none of the polishing regimens restored the polishability to the baseline level.
authors: University of Zürich, Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, Plattenstrasse 11, CH-8032 Zurich, Switzerland. Electronic address: mutluozcan@hotmail.com.
authors: Nadin
authors: N
authors: Al-Haj Husain
authors: University of Malta, Department of Restorative Dentistry, Faculty of Dental Surgery, Msida, Malta.
authors: Josette
authors: J
authors: Camilleri
authors: University of Zürich, Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, Plattenstrasse 11, CH-8032 Zurich, Switzerland.
authors: Mutlu
authors: M
authors: Özcan
mesh_terms: D003775:Dental Polishing; D018130:Diamond; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D018130:Diamond; D015040:Zirconium; C028541:zirconium oxide
keywords: Monolithic zirconia; Phase transformation; Polishing; Tribology; XRD; Y-TZP