Table 1.

Universal adhesives used in the experiment and their application methods.

Universal Adhesive	Abbreviation	Composition	Application Method	pH
All-Bond Universal (Bisco)	ABU	MDP, Bis-GMA, HEMA, ethanol, water, initiators	Apply for 10–15 s, mild air-dry for at least 10 s, light cure for 10 s	3.2
Prime & bond (DENTSPLY Caulk)	PB	MDP, Bis-GMA, HEMA, CQ, MCAP, D3MA, ethanol, water, highly dispersed silicon dioxide	Apply for 20 s, mild air-dry for 5 s, light cure for 10 s	2.5
Single Bond Universal (3M)	SBU	MDP, HEMA, silane, filler, dimethacrylate resins, water, Vitrebond copolymer, ethanol, initiators	Apply adhesive for 20 s, dry gently for 5 s, light cure for 10 s	2.7
Clearfil Universal Bond (Kuraray)	CUB	MDP, Bis-GMA, HEMA, CQ, hydrophilic aliphatic imethacrylate, colloidal silica, accelerators, silane coupling agent	Apply for 10 s, mild air-dry for 5 s, light cure for 10 s	2.3

MDP: 10-methacryloyloxydecyl dihydrogen phosphate, Bis-GMA: 2,2-Bis [4-(2-hydroxy-3-methacryloxypropoxy) phenyl] propane, HEMA: 2-hydroxyethyl methacrylate, CQ: camphorquinone, MCAP: Methacrylated carboxylic acid polymer, D3MA: Decandiol dimethacrylate.