Micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel

Purpose The aim of this study was to evaluate micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel. Materials and methods Extracted human molars were classified according to the severity of fluorosis using Thylstrup and Fejerskov index into four groups (TFI: 0, normal; 1–3, mild fluorosis; 3–6, moderate fluorosis; 6–7, severe fluorosis) and divided into following two sub-groups. For the first sub-group, a self-etching primer adhesive system was applied to the ground enamel surfaces and the other sub-group was conditioned with 37% phosphoric acid for 30 s prior to application of the same adhesive system. Teeth were then restored with a resin composite, stored for 24 h in water and micro-shear bond strengths were measured. After shear testing, the fracture modes were observed under a laser scanning microscope. Morphological study of etching patterns and adhesive interface was done under a scanning electron microscope (SEM). The data were analyzed using two-way ANOVA and Sheffe test (p=0.05). Results No statistically significant difference was there between the different degrees of fluorosis in each sub-group. However, significant difference in the bond strengths between phosphoric acid etching and self-etching was found in moderate and severe groups. The SEM observations showed at the resin-enamel interface, thick resin tag like extensions penetrated around 3.5 μm into the enamel etched with phosphoric acid, while self-etching primer created, 1 μm lamina like penetration. Conclusion Severity of fluorosis affects the micro-shear bond strength of a self-etching bonding system to fluorosed enamel.