Effect of different energy densities of CO2 laser on shear bond strength of resin cement to zirconia

The aim of the present study was to investigate the effect of different energy densities of 10,600 nm CO2 laser on the shear bond strength (SBS) of zirconia to resin cement.

Seventy-five zirconia disks (10 mm × 3 mm) were fabricated and randomly divided into five groups of 15 and underwent the following surface treatments: group 1, no treatment (control); group 2: sandblasting with 30-μm Al2O3 particles; groups 3, 4, and 5: irradiation with a CO2 laser with energy densities of 178.34 J/cm², 222.92 J/cm², and 267.51 J/cm², respectively. The surface morphology of one specimen from each group was investigated under SEM. Then, composite resin cylinders with 3 mm in diameter and 4 mm in height were fabricated. After applying ceramic primer to the zirconia ceramic surface, the composite cylinders were cemented to zirconia disks with resin cement and stored in distilled water for 24 h. Then, all samples were subjected to 2000 thermocycles of 5–55 °C. The SBS test was performed using a universal testing machine after thermocycling. The data were statistically analyzed by Welch and Games–Howell tests at 0.05 significance.

There was no significant difference between the mean SBS of the control group and178.34 J/cm² laser group. The mean SBS in the sandblast group was significantly higher than 178.34 J/cm² and 222.92 J/cm² laser groups and the control group. There was no significant difference between 222.92 J/cm² and 267.51 J/cm² laser groups. Despite adhesive failure observed in the control group, the failure mode was predominantly mixed in sandblast and laser groups.

Sandblast and 222.92 J/cm² and 267.51 J/cm² laser groups significantly increased SBS compared to the control group.