Evaluation of the Effect of Different Types of Abrasive Surface Treatment before and after Zirconia Sintering on Its Structural Composition and Bond Strength with Resin Cement

Abstract

This study evaluated the effect of air abrasion before and after sintering with different particle type, shape, and size on the surface morphology, monoclinic phase transformation, and bond strength between resin cement and zirconia surface using primer containing silane and MDP. Airborne particle abrasion (APA) was performed on zirconia before and after sintering with different particle shape and size (50 μm Al₂O₃ and 25 μm silica powder). 120 square shaped presintered zirconia samples (Amann Girrbach) were prepared (3 mm height × 10 mm width × 10 mm length) and polished with grit papers #800, 1000, 1200, 1500, and 2000. Samples were divided into 6 groups according to surface treatment-group A: (control) no surface treatment; group B: APA 50 μm Al₂O₃ before sintering (BS); group C: APA 50 μm Al₂O₃ after sintering (AS); group D: APA25 μm silica powder (BS); group E: APA25 μm silica powder (AS) at a pressure of 3.5 bar; and group F: APA 25 μm silica powder (AS) at a pressure of 4 bar. Samples were analyzed using XRD, AFM, and SEM. The samples were submitted to shear bond strength (SBS) test. A dual cure resin cement (RelyX Ultimate) and primer (Scotchbond Universal) were used. Data were analyzed with ANOVA and Tukey test (α ≥ 0.05). APA in group B significantly increased the surface roughness when compared to all other groups. A significant monoclinic phase transformation (t-m) value was observed in groups C and F and a reverse transformation occurred in presintered groups. The SBS value of group A was 11.58 ± 1.43 and the highest significant shear bond strength value was for groups B (15.86 ± 1.92) and C (17.59 ± 2.21 MPa) with no significant difference between them. Conclusions. The use of APA 50 μm Al₂O₃ before sintering and the application of primer containing MDP seem to be valuable methods for durable bonding with zirconia. The use of APA 50 μm Al₂O₃ after sintering induced the highest (t-m) phase transformation.

Figure 1

AFM images of groups: PS, GS, A, B, C, D, E, and F. Groups A, B, and D abraded before sintering showed a larger grain with clearly visible grain boundaries. Groups C, E, and F were abraded after sintering; group D only showed clearly visible grains, while groups C and E showed barely visible grain boundaries with smaller grains.

Figure 2

SEM and EDX analysis of groups B and C: failure loads in both groups were mixed and partly cohesive within the composite cylinders.

Figure 3

XRD of the studied groups A to F: groups C and F showed higher Xm%, reversed intensity of the tetragonal peaks t (002) and t (200), and a hump on the left shoulder of (101) t peaks. Groups C and F show decrease of the intensities of tetragonal peak (101).

Figure 4

SEM of groups A, B, D, and E. Groups A, B, and D treated before sintering appeared with deep grooves, round elevations, and grain coarsening. Abrasion of group E by silica particle after sintering did not change the surface texture.

Figure 5

SEM of groups A, C, E, and F. Group C abraded after sintering by 50 μm Al₂O₃ particles and group E abraded after sintering by 25 μm silica particles with 4-bar pressure appeared with pits, grooves, and sharp edges, while group D abraded by 25 μm silica particles after sintering with 3.5 bar appeared as control group.