Effect of Er:YAG laser pulse duration on repair bond strength of resin-based and hybrid CAD/CAM restorative materials

Besides the output power and pulse frequency, the pulse duration of Er:YAG laser is an important parameter for conditioning the restorative material surface. This study aimed to investigate the effect of six different pulse modes of Er:YAG laser on the repair bond strength of a hybrid ceramic and two resin-based CAD/CAM restorative materials. Twenty-eight specimens (5 × 5 × 4 mm) were prepared for each CAD/CAM block (Lava Ultimate-(LU), Vita Enamic-(VE), and GC Cerasmart-(GCC)) and randomly divided into seven groups. The specimens except the control group were irradiated using Er:YAG laser at 3 W and 20 Hz using quantum square pulse (QSP), super short pulse (SSP), short pulse (SP), medium short pulse (MSP), long pulse (LP), and a very long pulse (VLP). A micro-hybrid resin composite (Filtek Z250, 3 M ESPE, USA) was placed up to 4 mm on each CAD/CAM specimen in two increments. Bar specimens (1 × 1 × 8 mm) were obtained using a cutting device and thermocycled 10,000 times at 5–55 °C. Microtensile bond strength (µTBS) test was performed at a 1 mm/min crosshead speed. Data were statistically analyzed using two-way ANOVA and Tukey’s HSD tests (p < 0.05). µTBS was significantly affected by both pulse duration and material type (p < 0.001). Pulse duration and material type showed a statistically significant interaction (p < 0.001). Except for QSP, shorter pulse modes resulted in a higher repair bond strength. VLP mode is not recommended to be used in repair procedures with the materials tested.