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    Effect of airborne particle abrasion and sintering order on the surface roughness and shear bond strength between Y-TZP ceramic and resin cement
    (JAPANESE SOC DENTAL MATERIALS DEVICES, 2019) Okutan, Yener.; Yucel, Munir Tolga.; Gezer, Tugce.; Donmez, Mustafa Borga.
    This study examined the surface roughness (R-a) and shear bond strength (SBS) of Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic after airborne particle abrasion at different pressures and particle sizes, pre- and post-sintering. Ninety specimens, prepared from Y-TZP ceramic blocks (Vita In-Ceram YZ, Vita Zahnfabrik), were divided into nine subgroups: control, and 50 and 110 gm Al2O3 airborne particle abrasion at 3 and 4 bar pressure, before and after sintering, respectively. According to the sintering order, before and after surface treatments, R-a values were measured using a profilometer. SBS to Y-TZP was assessed after thermocycling, using self-adhesive resin cement (Rely X U200, 3M ESPE). Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were performed on one specimen per group. All surface-treated samples were rougher than the controls. ABS50-4 (50 mu m Al2O3 airborne particle abrasion at 4 bar pressure before sintering), ABS110-3, and ABS110-4 showed the highest R-a values, among all cohorts. The controls displayed lower SBS values than the treated groups (p<0.05), which had statistically similar results to each other. Airborne particle abrasion of pre-sintered Y-TZP, followed by sintering, increased the tetragonal structure contents.
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    Effect of surface treatments and aging on phase transformation and flexural strength of different Y-TZP ceramics
    (WILEY, 2019) Okutan, Yener.; Yucel, Munir T.
    This study aimed to evaluate the influence of surface treatments and artificial aging on surface roughness (Ra), phase transformation, and flexural strength of yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Two-hundred and eighty specimens from four types of Y-TZP were divided into seven groups, according to the surface treatments and aging used: control, air-abrasion, air-abrasion + aging, grinding, grinding + aging, erbium: yttrium-aluminum-garnet (Er:YAG) laser, Er:YAG laser + aging. The Ra values were measured using a profilometer. X-ray diffraction (XRD) analysis was performed to determine phase transformation. Specimens were subjected to a three-point bending test and loaded until fracture. Scanning electron microscope (SEM) and atomic force microscope (AFM) analyses were performed on one specimen per group. Grinding and air-abrasion groups exhibited higher Ra values than the others (P < 0.05). The differences in the roughness and flexural strength values between the laser and control groups were not significant. For all materials, the highest amount of monoclinic phase was found after air-abrasion. Grinding groups showed lower flexural strength values compared with the control groups (P < 0.05), while there was no significant difference between the control and air-abrasion groups. Aging did not affect the roughness and flexural strength (P > 0.05). The grinding process is not recommended in clinical usage for Y-TZP because of the remarkable decrease in flexural strength and reliability.