Shear Bond Strength of Composite to Zirconia Veneering Porcelains

Objective: Porcelain fracture has been reported as the second greatest cause for the replacement of all ceramic restorations after dental caries. The present project was designed to assess the shear bond strength of composite to zirconia specific porcelain after acid-etching the surface. Method: Eighty sintered zirconia blocks measuring 9 mm x 9 mm x 4 mm (Procera Y-TZP, Nobel Biocare AB, Gotebörg, Sweden) were veneered with 4 porcelains. Group A: GC Initial Zr (GC America, Alsip, IL, USA), Group B: Noritake CZR (Noritake Dental Supply co., Aichi, Japan). Group C: Lava Ceram (3M ESPE Dental Product, St. Paul, MN, USA). Group D: Nobel Rondo Porcelain (Nobel Biocare AB, Gotebörg, Sweden). GC Gradia Direct (GC America, Alsip, IL, USA) was bonded to the porcelain surfaces after acid etching with 9.6% hydrofluoric acid and silanization. All samples underwent thermocycling for 500 cycles between 5°C~55°C with a 30 seconds dwell time. All samples were subjected a shear load using an Instron machine (Instron, Norwood, MA, USA) until debonding occurred. Result: The shear bond strength in Megapascals were as follows: Control: Group A: 0.81±0.17, Group B:0.16±0.02, Group C:0.21±0.04, Group D:0.42±0.31. Acid Etching: Group A: 2.04±0.38, Group B: 6.73±0.46, Group C: 1.20±0.19, Group D: 2.29±0.22. Conclusions: Analysis reveals statistical significant differences between all acid-etching groups and control groups under the same porcelain category. In acid etching, Group B has significantly higher shear bond strength than all other groups. Supported by NobelBiocare/University of Michigan Center for Excellence