Figure 3. SEM views of the resin-dentin interface with various pH values of the aqueous solution for HEMA primer. Magnification: 5000 times. CR: Composite resin. H: Hybrid layer. Non-treated: Clearfil New Bond was applied to etched dentin without any primer pre-treatment. Clearfil SE Bond primer: After the ground dentin was conditioned with Clearfil New Bond primer, Clearfil New Bond and Clearfil SE-II were applied to the primed dentin. Treated: Etched dentin primed with HEMA solutions of different pH values. pH = 1.5: Distilled water ionized by HCl. pH = 6.6: Distilled and de-ionized water was used. pH = 12.0: Distilled water ionized by NaOH.