To evaluate the effect of different experimental primers containing 4-methacryloxyethyl trimellitate anhydride (4-META) and 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) on microshear bond strength (µSBS) and contact angle (CA) in different generations of zirconia. Two experimental primers were prepared: 1 wt% 10-MDP in an ethanol-water solution and 1 wt% 4-META in an acetone-water solution. A commercial primer (Clearfil Ceramic Primer Plus) served as the control. Three zirconia types (3Y-TZP, 4Y-PSZ, 5Y-PSZ) were conditioned and bonded with RelyX ARC resin cement. µSBS (n = 6) was measured after 48 h and after 5,000 thermocycles, and fracture patterns were assessed. CA measurements (n = 8) were obtained using the sessile drop method. Data were analyzed using two-way ANOVA and Tukey’s test (α = 0.05). Immediate µSBS showed no differences among primers for 3Y-TZP and 4Y-PSZ (p > 0.05), whereas 10-MDP yielded higher values on 5Y-PSZ compared with 4-META (37.04 ± 5.60 MPa vs. 28.53 ± 4.62 MPa; p = 0.028). After aging, 4-META showed significantly lower µSBS on 5Y-PSZ (8.27 ± 7.56 MPa) than 10-MDP and control (p < 0.001). For contact angle, 4-META produced lower values on 5Y-PSZ than on 3Y-TZP and 4Y-PSZ (p < 0.001), while 10-MDP had the lowest CA on 3Y-TZP (p = 0.002). Adhesive failures predominated. The 10-MDP primer showed stable bonding across all zirconia types, whereas 4-META exhibited reduced bonding stability, particularly on cubic-rich zirconias. These findings highlight the importance of zirconia composition and monomer chemistry in adhesion, indicating that simplified MDP-based formulations may provide effective bonding to high-translucency zirconias.
Santos et al. (Wed,) studied this question.