title: [Effect of hydrofluoric acid etching time on the resin bond durability of glass ceramic].
abstract: OBJECTIVE
  To analyze the effect of hydrofluoric acid (HFA) etching time on the resin bond durability of glass ceramic.
  
  
  METHODS
  Three groups of samples of machinable glass ceramic (ProCAD) were etched by 4.8% HFA for 0, 30 and 60 s respectively. The roughness parameters (Ra, Sm, S) and surface area of the samples, were measured with a 3D-laser scanning microscope. Then the ceramic surfaces were bonded with four resin cements (silane coupler/resin cement), which were Monobond S/Variolink II, Clearfil Ceramic Primer/Clearfil Esthetic Cement, GC Ceramic Primer/Linkmax HV, and Porcelain Liner M/SuperBond. The micro-bond strengths between the ceramic and the resin were tested at baseline and after the samples had been treated in 30000 thermal cycles.
  
  
  RESULTS
  The Ra [(3.89+/-1.94), (12.53+/-0.80), (13.58+/-1.10) microm] and surface area [(7.81+/-2.96), (30.18+/-2.05), (34.16+/-1.97) mm2] of ceramic increased with the increase of HFA etching time. The thermal cycling test reduced the bond strength of all test groups. The bond strength of Monobond S/Variolink II group [(3.59+/-3.51), (16.18+/-2.62), (20.33+/-2.45) MPa] and Clearfil Ceramic Primer/Clearfil Esthetic Cement group [(4.74+/-2.08), (7.77+/-1.55), (13.45+/-3.75) MPa] increased with the increase of HFA etching time; 30 s HFA etching group of Porcelain Liner M/SuperBond had higher bond strength [(22.00+/-1.64) MPa] than its 0 s HFA etching group [(12.96+/-4.17) MPa], and no significant difference was found between the 30 s and 60 s HFA etching groups of Porcelain Liner M/SuperBond [(20.42+/-3.01) MPa]. HFA etching time had no effect on the bond strength of GC Ceramic Primer/Linkmax HV.
  
  
  CONCLUSIONS
  HFA etching can improve the resin bond durability of glass ceramic, and the etching time is not only related to the change of ceramic surface roughness and area, but also to the characteristics of resins.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Nanjing University & Nanjing Stomatological Hospital, Nanjing 210008, China. mengsoar@nju.edu.cn
authors.forename: Xiang-feng
authors.initials: XF
authors.lastname: Meng
authors.forename: Xiao-lu
authors.initials: XL
authors.lastname: Zhou
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Luo
mesh_terms: D000134:Acid Etching, Dental; D002516:Ceramics / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis; D006858:Hydrofluoric Acid / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003738:Dental Cements; C470486:Linkmax; C076808:Monobond S; D019279:Resin Cements; C530542:clearfil esthetic cement; D003776:Dental Porcelain; C023506:Glass ceramics; D006858:Hydrofluoric Acid