Effect of Nd:YAG Laser Surface Pretreatments and Bonding Protocols on Shear Bond Strength of Monolithic Zirconia with Varying Yttria Contents to Composite Resin

This study aimed to evaluate the impact of different surface pretreatments and bonding protocols on the shear bond strength (SBS) of two monolithic zirconia materials to composite resin.A total of 200 zirconia specimens, 3Y-TZP (<i>n</i> = 100) and 5YSZ (<i>n</i> = 100), were allocated into five groups: Control with no treatment, air-particle abrasion (APA), Nd:YAG (neodymium-doped yttrium aluminum garnet) laser treatment (L), a combination of APA and L, and laser treatment followed by cold plasma (CAP). Half of the specimens received a primer application before bonding with resin cement. Surface morphology was assessed using scanning electron microscopy, and SBS testing was conducted with a universal testing machine.The SBS analysis was done using multiway analysis of variance (<i>p</i> ≤ 0.05).Different surface pretreatments and 10-methacryloyloxydecyl dihydrogen phosphate primer application significantly increased SBS values (<i>p</i> ≤ 0.001). APA was associated with the highest SBS values, followed by APA + laser and laser + CAP. However, the combination of APA with L slightly reduce the bond strength. While the application of laser alone possesses the lowest SBS among the surface pretreatment methods, the control group was the worst by far. Different zirconia materials showed no impact on SBS values.APA surface pretreatment might still be the gold standard for zirconia adhesion. Laser surface pretreatment is a viable, less destructive option. Combining APA with laser slightly reduces SBS, while combining two inert surface pretreatment methods, such as laser and CAP, leads to enhancement of SBS compared with laser alone. Zirconia primer is highly recommended for bonding protocol. No special considerations should be taken for different yttria contents, as both materials reported comparable bond strength within the same coupled variables.