Xp 504dr

Resin-infiltrated specimens were weighed after demineralization of the dentin beams (M₀), immediately following resin-infiltration (M₁), and after specimens were kept in distilled water for 24 h (M₂), 1 month, 3 and 6 months.
Dry mass (M₀ and M₁) was assessed after specimens were individually stored in a desiccator containing anhydrous calcium sulfate at 37 °C for 24 h. The specimens were, then, immersed in distilled water [28 (link)] for 24 h, 1 month, 3 months and 6 months in order to assess M_2, M_3, M_4, M_5, respectively. The excess water was wiped from the specimen surface using absorbent paper and then, they were immediately weighed [26 (link)] on an analytical balance (XP 504DR, Mettler Toledo Inc., Columbus, OH, USA).
The resin/dentin matrix ratio (R) was assessed using the formula [22 (link)]: R (%) = 100 – ((M₀x100)/M₁), where M₀ is the dentin matrix mass- after demineralization and M₁ is the dentin beam after the resin-infiltration. In addition, the percent mass change (Wmc %): was calculated according to the percentage mass gain of the adhesive resin beam or the resin-infiltrated dentin beam after immersion in 24 h of water storage using the formula [28 (link)]: Wmc (%) = (M₂-M₁)/M₁

One mL of each adhesive system was dispensed in a circular-plate and their initial mass was measured using an analytical balance (XP 504DR, Mettler Toledo Inc., Columbus, OH, USA). Each circular plate with the adhesive system was repeatedly weighed after 15, 30, 45 and 60 min until weight was stabilized. To keep traces of solvent in the adhesive, the time of volatilization was set at 30 min (based on pilot studies). The adhesive systems were kept in the dark for 30 min in an oven at 40 ± 1 °C or at room temperature (23 ± 1 °C). After time elaspsed, the adhesives were placed in polyvinyl siloxane molds (0.28 mm × 1.5 mm × 7.0 mm) and were immediately light-cured for 60 seconds on each side. Photo-activation was performed using a halogen-based unit (Optilux 501, Kerr Corp., Orange, CA, USA) with light intensity of 800 mW/cm². Then, all adhesive resin beams (n=12 per group) with final dimensions 0.28 mm thickness × 1.5 mm width × 7.0 mm length were hand-polished with 600-grit silicon carbide paper with a silicone oil emulsion (Sigma-Aldrich, St. Louis, MO, USA) [26 (link)].