title: Comparison of different grinding procedures on the flexural strength of zirconia.
abstract: BACKGROUND
  The surface of zirconia ceramic is damaged during grinding, which may affect the mechanical properties of the material.
  
  
  OBJECTIVE
  The purpose of this study was to compare the biaxial flexural strength of zirconia after different grinding procedures and to measure the temperature rise from grinding.
  
  
  METHODS
  Forty disk-shaped zirconia specimens (15 × 1.2 mm) with a smaller disk in the center of each disk (1 × 3 mm) were divided into 4 groups (n=10). The specimens were ground with a high-speed handpiece and micromotor with 2 different grinding protocols, continual grinding and periodic grinding (10 seconds grinding with 10 seconds duration), until the smaller disk was removed. Control specimens without the center disk (n=10) were analyzed without grinding. The biaxial flexural strengths of the disks were determined in a universal testing machine at a crosshead speed of 0.5 mm/min. The fracture strength (MPa) was recorded, and the results were analyzed using a 1-way ANOVA, Tukey HSD test, Student's t test, and Pearson correlation test (α=05).
  
  
  RESULTS
  All grinding procedures significantly decreased flexural strength (P<.01). The mean flexural strength of the high-speed handpiece groups was higher (815 MPa) than that of the micromotor groups (718 MPa). The temperature values obtained from micromotor grinding (127°C) were significantly higher than those from high-speed handpiece grinding (63°C) (P<.01).
  
  
  CONCLUSIONS
  Grinding zirconia decreased flexural strength. Zirconia material ground with a high-speed handpiece run continually caused the least reduction in flexural strength.
authors.affiliation: Department of Prosthodontics, Yeditepe University School of Dentistry, Goztepe, Istanbul, Turkey.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Işeri
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Ozkurt
authors.forename: Ayşe
authors.initials: A
authors.lastname: Yalnız
authors.forename: Ender
authors.initials: E
authors.lastname: Kazazoğlu
mesh_terms: D003755:Dental High-Speed Technique; D003775:Dental Polishing / Q000379:methods; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D008422:Materials Testing; D018583:Pliability; D013499:Surface Properties; D013696:Temperature; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide