title: Effect of cement shade and light-curing unit on bond strength of a ceramic cemented to dentin.
abstract: OBJECTIVE
  To evaluate the effect of cement shade, light-curing unit, and water storage on tensile bond strength (σ) of a feldspathic ceramic resin bonded to dentin.
  
  
  METHODS
  The dentin surface of 40 molars was exposed and etched with 37% phosphoric acid, then an adhesive system was applied. Forty blocks of feldspathic ceramic (Vita VM7) were produced. The ceramic surface was etched with 10% hydrofluoric acid for 60 s, followed by the application of a silane agent and a dual-curing resin cement (Variolink II). Ceramic blocks were cemented to the treated dentin using either A3 or transparent (Tr) shade cement that was activated using either halogen or LED light for 40 s. All blocks were stored in 37°C distilled water for 24 h before cutting to obtain non-trimmed bar-shaped specimens (adhesive area = 1 mm2 ± 0.1) for the microtensile bond strength test. The specimens were randomly grouped according to the storage time: no storage or stored for 150 days in 37°C distilled water. Eight experimental groups were obtained (n = 30). The specimens were submitted to the tensile bond strength test using a universal testing machine at a crosshead speed of 1 mm/min. The data were statistically analyzed using ANOVA and Tukey's posthoc tests (a = 0.05).
  
  
  RESULTS
  The mean bond strength values were significantly lower for the corresponding water stored groups, except for the specimens using A3 resin cement activated by halogen light. There was no significance difference in mean bond strength values among all groups after water storage.
  
  
  CONCLUSIONS
  Water storage had a detrimental effect under most experimental conditions. For both cement shades investigated (Tr and A3) under the same storage condition, the light-curing units (QTH and LED) did not affect the mean microtensile bond strengths of resin-cemented ceramic to dentin.
authors.affiliation: Department of Dental Materials and Prosthodontics, Sao Paulo State University at Sao Jose dos Campos, Brazil.
authors.forename: Humberto Lago
authors.initials: HL
authors.lastname: de Castro
authors.forename: Sheila Pestana
authors.initials: SP
authors.lastname: Passos
authors.forename: Lucas Villaça
authors.initials: LV
authors.lastname: Zogheib
authors.forename: Alvaro Della
authors.initials: AD
authors.lastname: Bona
mesh_terms: D000704:Analysis of Variance; D002516:Ceramics; D003116:Color; D055117:Curing Lights, Dental; D001840:Dental Bonding; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000528:radiation effects; D006801:Humans; D019279:Resin Cements / Q000528:radiation effects; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D014867:Water
chemical_list: D017220:Dentin-Bonding Agents; D019279:Resin Cements; C556625:VITA VM7; D014867:Water; D003776:Dental Porcelain; C103502:Variolink