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TUNCEL, İLKİN

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İLKİN
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TUNCEL
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    PublicationOpen Access
    Effects of coloring procedures on shear bond strength between resin cement and colored zirconia.
    (2018-09-01) TUNCEL, İLKİN; Turp, IŞIL; TUNCEL, İLKİN; TURP, IŞIL
    Zirconia has a high fracture strength of more than 1000 MPa, fracture resistance of higher than 2000 N, and fracture toughness of 9–10 MN/m3/2 (1). In addition to these favorable mechanical properties, it is chemically durable (2), biocompatible (3, 4), and displays esthetic advantages (5) over metal-ceramic restorations. However, recent clinical trials have shown that zirconia-based ceramic restorations’ decementation is a common failure. Restoration’s cementation corresponds to restoration durability, and cementation is also an important factor for marginal fit and fracture strength of restorations (6, 7). There are various cementation options for zirconia framework restorations. Cementation of zirconia restorations with traditional luting cements (such as glass ionomer or zinc phosphate cements) provides adequate clinical fixation, but adhesive cementation may be preferred for better retention and marginal adaptation (7-10). In addition, resin cement shows higher compressive and tensile strength than other luting agents, and allows color selection for more esthetic restorations (11, 12).
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    PublicationOpen Access
    Evaluation of translucency of monolithic zirconia and framework zirconia materials.
    (2016-06-01) TUNCEL, İLKİN; Turp, IŞIL; USUMEZ, A; TUNCEL, İLKİN; TURP, IŞIL
    PURPOSE. The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS. The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of 15×12×0.5 mm. A spectrophotometer was used to measure the contrast ratio, which is indicative of translucency. Three measurements were made to obtain the contrast ratios of the materials over a white background (L*w) and a black background (L*b). The data were analyzed using the one-way analysis of variance and Tukey HSD tests. One specimen from each group was chosen for scanning electron microscope analysis. The determined areas of the SEM images were divided by the number of grains in order to calculate the mean grain size. RESULTS. Statistically significant differences were observed among all groups (P<.05). Non-colored zirconia had the highest translucency with a contrast ratio of 0.75, while monolithic zirconia had the lowest translucency with a contrast ratio of 0.8. The mean grain sizes of the noncolored, colored, and monolithic zirconia were 233, 256, and 361 nm, respectively. CONCLUSION. The translucency of the zirconia was affected by the coloring procedure and the grain size. Although monolithic zirconia may not be the best esthetic material for the anterior region, it may serve as an alternative in the posterior region for the bilayered zirconia restorations. [J Adv Prosthodont 2016;8:181-6]
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    PublicationOpen Access
    Effect of color shading procedures and cyclic loading on the biaxial flexural strength of zirconia.
    (2018-01-01) TUNCEL, İLKİN; Turp, IŞIL; USUMEZ, A; TUNCEL, İLKİN; TURP, IŞIL
    Purpose: Zirconia is the most preferred ceramic restoration in posterior areas because of its flexural strength. The aim of the study is the evaluation of biaxial flexural strength of different colored zirconium oxide core materials after cyclic loading. Material and Methods: Zirconia discs (12 mm diameter and 1.2 mm thickness) were divided into 6 groups of 12 discs each. Groups were colored according to the Vita Classic shade guide: A3 and D4. One group was not colored and left as control. Each group was randomly divided into subgroups and subjected to mechanical cycling prior to biaxial flexural strength test. Cyclic loading was applied as 50 N loads for 20,000 times for the loaded groups. Samples were subjected to biaxial flexural strength test in a universal testing machine with a crosshead speed of 1 mm/min. Two-way analysis of variance (ANOVA) and Tukey's HSD tests were used for comparisons of the groups. Results: Biaxial flexural strength values did not vary significantly depending on coloring procedure or loading process tested (p>.05). XRD analysis displayed that the monoclinic volume fraction of zirconia was highest in cyclic loaded D4 and was lowest in non-loaded control group. The SEM image revealed that A3 color solution created metallic coloring pigments at grain boundaries. Conclusions: Coloring procedures and cyclic loading did not affect the biaxial flexural strength of zirconia core material; however, microstructural analysis displays changes, which may weaken the zirconia structure on the long term.