Impact of Silanized Nanographene Oxide Concentrations in Different Primers on Bonding Durability between Resin Cement and Zirconia.

Objectives:  Zirconia (ZrO₂) has been used in dental restorations due to its increased mechanical properties, biocompatibility, low degree of bacterial adhesion, and acceptable optical properties. One of the major drawbacks of ZrO₂ is its short-term durable bond with resin cement. The objective of this study was to evaluate the effect of different primers embedded with silanized nanographene oxide (SGO) sheets on the wettability of ZrO₂ surface and bond strength durability between resin cement and ZrO₂.

Materials and methods:  Four hundred ZrO₂ specimens were divided into four main groups as each group had 100 specimens according to the type of the primer: rely X ceramic primer (Group I), monobond N primer (Group II), monobond plus primer (Group III), and Z prime plus primer (ZP, Group IV). Each main group was subdivided into five subgroups according to SGO concentrations by weight blended into primers: (1) 0% (control), (2) 0.1%, (3) 0.3%, (4) 0.6%, and (5) 0.9% as each subgroup had 20 specimens. Immediate shear bond strength (SBS) test was done for half of the specimens per each subgroup (10 specimens) by universal testing machine, the other half of the specimens per each subgroup (10 specimens) were exposed to thermocycling for 10,000 cycles that is equivalent to 1 year of clinical use at controlled temperatures (5-55°C) by thermocycler then SBS test by universal testing machine was done. Water contact angle test was done for all specimens per each subgroup (20 specimens) by computer software and an optical tensiometer.

Results:  The SBS was nonsignificantly decreased after thermocycling for all primers embedded with SGO except for ZP primer. The best wettability of ZrO₂ surface was found in (ZP) primer group embedded with (0.9% SGO) with a mean value of 20.60.

Conclusion:  Primers embedded with SGO could increase the wettability of the ZrO₂ surface and bond strength durability between resin cement and ZrO₂ even after thermocycling aging. The clinical significance of this study was the possible increase of the wettability of ZrO₂ surface and SBS of resin cement to ZrO₂ with promising long-term stability when commercial primers embedded with SGO were used. This could reduce the risk of debonding between resin cement and ZrO₂ crowns or veneers.