INFLUENCE OF DIFFERENT BLEACHING SYSTEMS ON THE BOND STRENGTH OF LAMINATE VENEER TO ENAMEL

Purpose: The objective of this in-vitro study was to examine the microtensile bond strength of a porcelain laminate veneer (PLV)  to tooth surface bleached with photoactivation by blue light-emitting diode (LED) or diode laser. Methods: Eigthteen extracted human central incisors were randomly divided into three groups. Two sticks were obtained from each tooth (n=12). Before surface treatments; teeth were prepared to provide space for PLVs. The first group teeth were bleached with Whiteness HP which is contain 35% hydrogen peroxide (HP) and then photoactivated with a LED for 20 seconds. The second  group were bleached with Laserwhite 20  which is contain 46% HP and  photoactivated with a diode laser for 30 seconds. The third group received no surface treatment and served as the control group. IPS Esthetic ceramic veneers were luted with Variolink II veneer cement . The teeth were sectioned to obtain porcelain-resin-enamel/dentin sticks and submitted to a MTB testing device. The maximum load at fracture  was recorded. Data were analyzed using one-way ANOVA followed by the Tukey HSD post-hoc test at a preset  I± of  0.05. Results: One-way ANOVA revealed that there was significant difference between LED unit group and control group (p .05)  The LED unit group presented significantly lower bond strength value (6.49±2.3 MPa) than diode laser (8.49 ±3.1 MPa) and control groups (9.53±2.7 MPa). Conclusion: The results suggested that bleaching therapy with activation by LED or diode laser reduced the bond strength of IPS Esthetic ceramic veneers to tooth surfaces. Keywords: Teeth Bleaching; Photoactivation; Semiconductor lasers; Diode laser; Microtensile.