title: Effect of composite surface treatment and aging on the bond strength between a core build-up composite and a luting agent.
abstract: OBJECTIVE
  The purpose of this study was to assess the influence of conditioning methods and thermocycling on the bond strength between composite core and resin cement.
  
  
  METHODS
  Eighty blocks (8×8×4 mm) were prepared with core build-up composite. The cementation surface was roughened with 120-grit carbide paper and the blocks were thermocycled (5,000 cycles, between 5°C and 55°C, with a 30 s dwell time in each bath). A layer of temporary luting agent was applied. After 24 h, the layer was removed, and the blocks were divided into five groups, according to surface treatment: (NT) No treatment (control); (SP) Grinding with 120-grit carbide paper; (AC) Etching with 37% phosphoric acid; (SC) Sandblasting with 30 mm SiO2 particles, silane application; (AO) Sandblasting with 50 mm Al2O3 particles, silane application. Two composite blocks were cemented to each other (n=8) and sectioned into sticks. Half of the specimens from each block were immediately tested for microtensile bond strength (µTBS), while the other half was subjected to storage for 6 months, thermocycling (12,000 cycles, between 5°C and 55°C, with a dwell time of 30 s in each bath) and µTBS test in a mechanical testing machine. Bond strength data were analyzed by repeated measures two-way ANOVA and Tukey test (α=0.05).
  
  
  RESULTS
  The µTBS was significantly affected by surface treatment (p=0.007) and thermocycling (p=0.000). Before aging, the SP group presented higher bond strength when compared to NT and AC groups, whereas all the other groups were statistically similar. After aging, all the groups were statistically similar. SP submitted to thermocycling showed lower bond strength than SP without thermocycling.
  
  
  CONCLUSIONS
  Core composites should be roughened with a diamond bur before the luting process. Thermocycling tends to reduce the bond strength between composite and resin cement.
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, UNESP, São José dos Campos, SP, Brazil.
authors.forename: Caroline
authors.initials: C
authors.lastname: Cotes
authors.affiliation: University Veiga de Almeida, Rio de Janeiro, RJ, Brazil.
authors.forename: Mayra
authors.initials: M
authors.lastname: Cardoso
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, UNESP, São José dos Campos, SP, Brazil.
authors.forename: Renata Marques de
authors.initials: RM
authors.lastname: Melo
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, UNESP, São José dos Campos, SP, Brazil.
authors.forename: Luiz Felipe
authors.initials: LF
authors.lastname: Valandro
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, UNESP, São José dos Campos, SP, Brazil.
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Bottino
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D019232:Dental Restoration Failure; D008422:Materials Testing; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D003188:Composite Resins; D010756:Phosphoric Acids; C528569:Rely-X; D019279:Resin Cements; D012821:Silanes; D012822:Silicon Dioxide; C030242:phosphoric acid