title: Influences of multiple firings and aging on surface roughness, strength and hardness of veneering ceramics for zirconia frameworks.
abstract: OBJECTIVE
  To evaluate the effects of multiple firings and aging on surface roughness, strength, and hardness of veneering ceramics for zirconia frameworks.
  
  
  METHODS
  Five different veneering ceramics for zirconia frameworks were used: Vintage ZR (ZR), Cerabien ZR (CZR), VitaVM9 (VM9), Cercon ceram KISS (KISS), and IPS e.max ceram (e.max). Specimens were fired 2 or 10 times in order to accelerate aging. Surface roughness was evaluated using laser profilometry. Flexural strength and Vickers hardness were also measured. Surface topography was observed using scanning electron microscopy.
  
  
  RESULTS
  After accelerated aging, the surface roughness of all specimens fired 10 times was significantly lower than that of the same specimens fired 2 times (P=0.000). Except for VM9, the flexural strength of all specimens fired 10 times was greater than that of the same specimens fired 2 times, and the differences were significant for ZR and CZR (P<0.01). The flexural strength of VM9 fired 10 times was significantly lower than that of VM9 fired 2 times (P=0.034). The Vickers hardness of ZR and VM9 fired 10 times was significantly higher than that of the same specimens fired 2 times (P<0.05), but that of KISS fired 10 times was significantly lower than that of KISS fired 2 times (P=0.000).
  
  
  CONCLUSIONS
  Multiple firings had a positive effect on the surface roughness of all aged veneering ceramics used for zirconia restorations and on the strength and hardness of many aged veneering ceramics used for zirconia restorations.
authors.affiliation: Department of Stomatology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China; Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan. Electronic address: t-xuehua2008@hotmail.com.
authors.forename: Xuehua
authors.initials: X
authors.lastname: Tang
authors.affiliation: Department of Stomatology, Jinling Hospital, Nanjing University School of Medicine, Nanjing 210002, China.
authors.forename: Huinan
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Oral Medicine, Institute and Hospital of Stomatology, Nanjing University School of Medicine, Nanjing 210008, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yatani
mesh_terms: D003776:Dental Porcelain / Q000737:chemistry; D003801:Dental Veneers; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013499:Surface Properties; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Accelerated aging; Flexural strength; Multiple firings; Surface roughness; Veneering ceramics; Vickers hardness