Shear bond strength of resin cement to additively manufactured zirconia with customized surface texture and porosity: Part 1.

STATEMENT OF PROBLEM: The additive manufacturing of zirconia has been reported to present promising mechanical properties. However, studies on bonding to additively manufactured (AM) zirconia are lacking. PURPOSE: The purpose of this in vitro study was to investigate the effect of customized porosity and surface texture on the shear bond strength (SBS) of resin cement to 3-dimensionally (3D) printed zirconia. MATERIAL AND METHODS: A total of 60 zirconia disks (O12x5 mm) were designed with different surface porosity using a computer-aided design (CAD) software program and manufactured via stereolithography (SLA) 3D printing. The disks were divided into 4 groups (n=15) based on surface texture and porosity: Control (no designed porosities), G1:50 (50x50-microm pores 200 microm apart), G2:100 (100x100-microm pores 400 microm apart), and G3:200 (200x200-microm pores 800 microm apart). The specimens were cleaned, and the binder removed before sintering. The microstructural analysis of the specimen's surface before SBS was performed using a profilometer to determine surface texture (n=5). SBS was measured using a universal testing machine, and thermal cycling was performed to simulate aging (n=10). Data for SBS were analyzed using 2-way ANOVA (alpha=.05). RESULTS: Surface texture and porosities were confirmed by profilometry. In all comparisons, the G3:200 group demonstrated the highest mean SBS with 8.78 MPa (P<.001); however, it was similar to the Control group, which had a mean of 8.41 MPa (P=.631). The G1:50 showed significantly lower SBS values at 3.90 MPa (P<.001), followed by the G2:100 group with 5.14 MPa (P<.001). Thermal cycling generally decreased SBS in all groups (P<.001). CONCLUSIONS: Customized surface textures can improve bond strengths, with larger pores (200x200 microm) providing values comparable with those of traditional mechanical pretreatments surfaces, while smaller pores resulted in lower bond strengths. This approach avoids surface damage and phase transitions caused by traditional treatments. These findings provide a foundation for future research aimed at developing more durable and reliable zirconia restorations, ultimately enhancing clinical outcomes.