Shafiei F, et al. - In this investigation, researchers assessed the impact of alloy/zirconia primer and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin layer treatments on the shear bond strength (SBS) of composite resin to zirconia after aging. Sixty zirconia blocks were air-abraded and divided into six experimental groups (n = 10) in terms of primer/resin layer as follows: control, without any primer or resin; AP, Alloy Primer; ZPP, Z-Prime Plus; PL/ZPP, Z-Prime Plus with light polymerization; AP+SEB, Alloy Primer along with light-cured bonding resin of a self-etch adhesive system (SE Bond); and ZPP+SEB, Z-Prime Plus with SE Bond. A universal testing machine was used to test the SBS. According to findings, various primers/resin layers influenced the bond strength between zirconia ceramic and composite resin. The application of an MDP-containing resin layer together with both primers led in a substantial improvement of SBS. For Z-Prime Plus, this improvement was considerably higher than for Alloy Primer.