Influence of Er;Cr:YSGG Laser on Shear Bond Strength and Color Stability of Lithium Disilicate Ceramics: An In Vitro Study

Objective: The aim of this study was to assess the effect of Er;Cr:YSGG laser parameters (power and frequency) on the bond strength and color stability of lithium disilicate (LD) ceramics. Materials and methods: One hundred ten specimens of LD ceramic were fabricated following heat pressed technique. Fifty disks were randomly distributed into five groups according to types of surface treatment [hydrofluoric (HF) acid, L1S L2S, L1D, and L2D]. For all laser-treated groups, bond preparation settings were used with a gold hand piece using a MZ10 tip (Er;Cr:YSGG, water lase I plus; Biolase). After surface treatment, adhesive bond was applied, and after photopolymerization, a composite buildup was performed. To evaluate shear bond strength, a controlled force was applied until failure using a universal testing machine. Color stability was assessed for six groups (HF, L1S L2S, L1D, L2D, and control) of LD ceramic (shade A1, LT translucency) through the CIE L*a*b* system. Three specimens from each of the six groups were selected randomly for assessment of surface topography using scanning electron microscopy. Means and standard deviations were compared using analysis of variance and Tukey's post hoc test (p<0.05). Results: The maximum and minimum mean bond strength were shown by the L2D group 19.951.014 and L1S group specimens 14.68 +/- 0.863, respectively. Highest mean Delta E was found in L2S group 8.17 +/- 2.10 and the lowest mean Delta E was found in control group (no treatment) 0.11 +/- 0.05. Conclusions: LD specimens lased (Er;Cr:YSGG) with 3.75 W power and 15Hz frequency for 4min showed bond strength comparable with HF acid samples, and color changes within acceptable range (Delta E 1.17). Laser treatment (Er;Cr:YSGG) at 3.75 W power and 15Hz frequency for 4min of LD ceramics appears to be clinically efficient, showing acceptable bond strength and color stability.