RESUMO
Conventional surface roughening treatments used for silica-based ceramics in order to improve subsequent adhesion become unreliable for zirconia ceramics. Laser conditioning can be a good alternative. The purpose of this in vitro study was to compare conventional (macro) shear bond strength (SBS) values obtained between resin composite and zirconium oxide ceramic samples grouped according to different micromechanical treatments received, and examine differences in surface roughness. One-hundred and fifty disks of sintered zirconia were randomly divided into 5 groups and roughened as follows: (1) Group NOT, no surface treatment; (2) Group APA, abraded with 50-µm aluminum-oxide (Al2O3) particles; (3) Group TBS, abraded with 30-µm aluminum-oxide particles covered with silica; (4) Group CO2, irradiated with a CO2 laser which emitted in continuous wave mode at 3 W of power; and (5) Group FEM, irradiated with a pulsed femtosecond laser, with an incident energy of 10 µJ, a frequency of 1000 Hz, and a fluence of 1.3 kJ/cm2. All surfaces were treated with a MDP-containing adhesive/silane coupling agent mixture upon which were prepared and light polymerized composite resin cylinders. Shear bond strength was measured and samples were observed by scanning electron microscopy (SEM). Statistically significant differences (p < 0.05) were found among all groups, except between CO2 and FEM, which showed the highest adhesion values (15.12 ± 2.35 MPa and 16.03 ± 2.73 MPa). SEM revealed differences in surface patterns. CO2 laser irradiation can be an alternative to sandblasting, although it could also weaken the ceramic. Suitable surface patterns on zirconia ceramics can be obtained with ultrashort pulsed radiation emitted by a pulsed femtosecond laser.
