Filtek supreme ultra

Sound human third molars (IRB no. 2018–0346) were selected and ground flat with silicon carbide (SiC) abrasive paper (180-, 320-grit, Buehler, Lake Bluff, IL, USA) to remove the occlusal enamel and expose mid-coronal dentin. Dentin surfaces were polished (600-grit for 20 seconds) to produce a smear layer. Specimens were randomly divided into 3 groups (n = 8) according to the experimental adhesive. Dentin surfaces were etched with 35 wt% glycolic acid (pH = 1.30, Sigma Aldrich, St. Louis, MO, USA) for 15 s and rinsed with ultrapure water (15 s). A bioactive primer consisting of 15 wt% VVe diluted in HEPES solution (pH = 7.2) was actively applied for 1 min and rinsed for 15 s. Then, two layers of the experimental adhesive containing 0% (control), 1.5 wt% of sub-micron (SM) or micron (M) VVe-filled PLA spheres were applied, air-dried for solvent evaporation and light cured for 40s (600 mW/cm², Optilux 501, Kerr Corp., Brea, CA, USA). A commercial light-curable resin composite (Filtek Supreme Ultra, Lot: N820171, 3M ESPE, St. Paul, MO, USA) was used to incrementally build a crown-like block. All specimens were immersed in simulated body fluid (SBF: 50 mM HEPES, 5 mM CaCl₂·2 H₂O, 0.001 mM ZnCl₂, 150 mM NaCl, and 3 mM NaN₃, pH = 7.4) [20 (link)], at 37°C. SBF was replaced every 15 days.