Objectives: To investigate the effect of various etching protocols on the surface roughness of composites with different filler compositions.
Methods: From a micro-hybrid composite containing barium-glass (Clearfil AP-X, Kuraray) and a nano-hybrid composite containing zirconia/silica nanoclusters (Filtek Supreme XT, 3M ESPE), specimens of 3mm thick with a diameter of 7mm were prepared (n=24). The top surface was polished with 4000-grit abrasive paper and subjected to one of eight surface treatment techniques (n=3): negative control, phosphoric acid for 20sec (H3PO4), 3% hydrofluoric acid for 20sec (3%HF-20sec), for 120sec (3%HF-120sec), 9.6% hydrofluoric acid for 20sec (9.6%HF-20sec), for 120sec (9.6%HF-120sec), H3PO4 followed by 9.6%HF-120sec (H3PO4-HF), and 9.6%HF-120sec followed by H3PO4 (HF-H3PO4). Roughness (Sa) was measured using a 3D-noncontact optical interferometer (WYKO, Veeco) and SEM evaluation was performed. ANOVA and posthoc Tukey HSD multiple comparisons were used to determine statistical differences in roughness between groups (p<0.05).
Results: The micro-hybrid barium-containing composite demonstrated a significant rougher surface than the nano-hybrid zirconium-containing composite (p<0.05). For the micro-hybrid composite, 3%HF-20sec, 3%HF-120sec and 9.6%HF-20sec resulted in a significant increase in roughness (p<0.001). For the nano-composite, only 3%HF-20sec and 9.6%HF-20sec showed an increase in roughness (p<0.02). For both composites, 9.6%HF-120sec, PA-HF and HF-PA resulted in a large increase in roughness compared to control (p<0.001). From SEM images, it was found that the micro-hybrid composite was much more affected by etching than the nano-hybrid composite.
Conclusions: The surface roughness after etching is largely affected by the composition of the filler particles in the composite.