Bonding to zirconia elucidating the confusion
Due to inequality of variances, Welch test was applied for data analysis.The Games-Howell test was used to compare different groups due to inequality of variances and being less conservative than the Tamhane’s test as well as small sample size yet more than 5 (n=15).The load was applied at a crosshead speed of 0.5 mm/min and load at fracture was recorded.The microshear bond strength value was calculated using the formula below: Debonded surfaces were then evaluated under a light stereomicroscope (Carl Zeiss, Germany) to determine the mode of failure.Sandblasted samples comprised the positive controls in our study for the purpose of comparison with other surface treatment methods.Many researchers believe that sandblasting with aluminum oxide particles is the most effective surface treatment to improve the bond to zirconia since it increases the surface roughness and results in micromechanical interlocking of luting cement [28-31].  recommended sintered zirconia sandblasting with 50 μ particles.
It has been confirmed that application of Nd: YAG laser to feldspathic ceramic prior to cementation increases its bond strength compared to etching with hydrofluoric (HF) acid .
All discs were placed in an ultrasonic bath containing 96% ethanol for 10 minutes for cleaning prior to surface treatment and were then dried.
Samples were then randomly divided into four groups (n=15).
We also used 50 μ alumina particles for sandblasting and obtained a high surface roughness and bond strength compared to the control group.
Roughening the internal surface of ceramic restorations can increase the available surface area for cement penetration and subsequently improves the mechanical bond .