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 M2, M3, M4, M5, 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