Effect Of Coupling Agents On Graded Zirconia-Glass Composite Bonding

This study evaluated the impact of coupling agents on the shear bond strength (SBS) of graded zirconia-glass composite surfaces before and after aging. A graded zirconia-glass composite surface was created by melt-infiltrating Si-Li-Al glass into fully sintered zirconia. The composite surface was acid-etched (hydrofluoric acid for 80 seconds) and treated with either (A) silane + 10-MDP-containing coupling agents or (B) 10-MDP-containing coupling agents. Composite resin cylinders (Ø3.5 mm × 2 mm) were bonded using 10-MDP-containing resin cement. Specimens were divided into immediate testing (24 h/37°C water storage) and aged testing (5,000 thermal cycles) subgroups. A control group received sandblasting + MDP resin. SBS was measured via universal testing machine with failure mode analysis conducted. Both coupling agent groups demonstrated significantly higher immediately and aged SBS than sandblasted control. Groups A and B showed comparable immediate bond strengths (p>0.05). However, Group B exhibited a significant SBS decrease after aging, while Group A maintained stable strength. No interfacial failure occurred in coupling agent groups. Coupling agents with silane and 10-MDP improved the bond strength with greater aging resistance in bonding to composite surfaces, offering better long-term stability than those with 10-MDP alone.