Hydrophilic Dental Adhesive Formulation

The model adhesive consisted of HEMA (Sigma-Aldrich, St. Louis, MO, USA) and BisGMA (Sigma-Aldrich, St. Louis, MO, USA) with a mass ratio of 45/55 (HEMA/BisGMA). The photoinitiators used were as follows: 0.5 wt% camphorquinone (CQ) as a hydrophobic photosensitizer, 0.5 wt% ethyl-4-(dimethylamino)benzoate (EDMAB) as a hydrophobic reducing agent, and 1.0 wt% diphenyliodonium hexafluorophosphate (DPIHP) as a hydrophilic coinitiator (all from Sigma-Aldrich, St. Louis, MO, USA). The neat resins were prepared in brown glass vials and stirred for 48 h to form a homogeneous solution [15 (link)].
D₂O (99.9%; Sigma-Aldrich, St. Louis, MO, USA) was added into the neat resins in variable amounts: 0 wt%, 10 wt%, and 16 wt%, based on [5 (link)]. These concentrations of D₂O were added according to a ternary phase diagram [16 (link)]. D₂O (heavy water) was used instead of water to avoid coincidence of the peaks at the spectrum in the FTIR [16 (link)].