title: Effect of hydrofluoric acid concentration and etching duration on select surface roughness parameters for zirconia.
abstract: BACKGROUND
  The surface of zirconia is resistant to chemical treatment. Roughening the surface of densely sintered zirconia still poses a challenge in dentistry.
  
  
  OBJECTIVE
  The purpose of the study was to examine the effects of hydrofluoric acid on the quality of surface roughening of zirconia.
  
  
  METHODS
  One hundred cylindrical disks made from zirconia (Ceramill Zi; Amann Girrbach AG) were divided into 4 groups. Three groups (n=30) were distinguished on the basis of hydrofluoric acid (HF) concentration: 40% HF, 9.5% HF, and 5% HF. The groups were then further divided into 3 groups of 10 specimens, each based on etch time (1, 5, or 15 minutes). The control group (n=10) consisted of specimens polished with SiC abrasive paper. The surface was examined with scanning electron microscopy, and the roughness was measured with a profilometer and confocal laser scanning microscope. The mean arithmetic profile deviation (Ra(mean)) and mean maximum height of profile (Rz(mean)) results for the etched surfaces in relationship to the baseline surfaces were compared with the Student t test for averaged data (α=.05).
  
  
  RESULTS
  When etched with 40% HF concentration, the Ra(mean) and Rz(mean) results were statistically higher (P<.01) for the etched surfaces than for the baseline surfaces. When etched with 9.5% HF concentration, the higher Ra(mean) and Rz(mean) results were only statistically significant (P<.01) after 15 minutes. Etching with 5% HF concentration showed no significant differences (P>.05).
  
  
  CONCLUSIONS
  Etching with a 5% HF solution should not be recommended as a method for roughening zirconia surfaces.
authors: Assistant Professor, Department of Dental Prosthetics, Medical University of Lodz, Lodz, Poland. Electronic address: bsmielak@hotmail.com.
authors: Beata
authors: B
authors: Smielak
authors: Professor, Department of Materials Research, Institute of Materials Science and Engineering; Professor and Chairman, Department of Dental Technology, Medical University of Lodz, Lodz, Poland.
authors: Leszek
authors: L
authors: Klimek
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D006858:Hydrofluoric Acid / Q000008:administration & dosage / Q000737:chemistry*; D008422:Materials Testing; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D017554:Carbon Compounds, Inorganic; D003764:Dental Materials; D017655:Silicon Compounds; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium; D006858:Hydrofluoric Acid; C022088:silicon carbide