Yazar "Yildirim, G." seçeneğine göre listele

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    Comparison of Time-dependent Two-dimensional and Three-dimensional Stability with Micro-computerized Tomography and Wettability of Three Impression Materials
    (Wolters Kluwer Medknow Publications, 2018) Karaaslan, G.; Malkoc, M. A.; Yildirim, G.; Malkoc, S.
    Objectives: The objective of this study is to explore time-dependent dimensional stability of three different elastomeric impression materials -vinyl polyether silicone (VPES), vinyl polysiloxane (VPS), and polyether (PE) -through micro-computerized tomography (mu -CT) imaging, allows three-dimensional (3D) imaging and measurement without sample preparation or chemical fixation. Materials and Methods: Thirty specimens were created using 3 mm high, 30 mm wide Teflon molds (n = 10). Specimens were scanned with mu -CT on the 1st (T1) h and 1st (T2), 7th (T3), and 14th (T4) days. 3D models were created at the above-mentioned times, volumetric measurements were conducted and dimensional changes were calculated. Diameters and heights of each impression material were measured with 2D analyses. Furthermore, contact angle measurements of these elastomeric impression materials were collected using the sessile drop method during and after polymerization at 0, 2, 5, 20, 60, 120, and 240 s These measurements were made on specimens (n = 10) prepared in standard sizes using a 50 mu m deep stainless steel die with dimensions of 62 mm x 20 mm x 3 mm. Results: Evaluation of the dimensional volume changes of the VPES, VPS, and PE measurements showed there to be no statistically significant differences between the T1, T2, T3, and T4 (P > 0.05). Only the decreases in the volume averages of T3 and T4 in the VPES were statistically significant (P < 0.05). As a result of binary comparisons, the evaluation of contact angle measurements of VPES, VPS, and PE materials during and after polymerization were compared. The average contact angle measurements of the VPS group were statistically significantly lower than the averages of the VPES and PE groups (P < 0.01). Conclusions: VPS was found to be the most stable impression material concerning dimensional change and wettability.
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    Effect of Different Acid Treatments on the Shear Bond Strength of Computer-Aided Design and Manufacturing (CAD-CAM) Ceramics for Dental Applications
    (Goller Verlag Gmbh, 2018) Yildirim, G.
    The purpose of this in vitro study was to compare the shear bond strengths (SBS) of hybrid ceramic; Vita Enamic (VE), zirconia-reinforced lithium silicate ceramic; Vita Suprinity (VS), feldspathic ceramic; Vita TriLuxe forte (VT), and lithium disilicate ceramic; IPS e.max CAD (IPS). Eighty specimens were prepared from four different CAD-CAD ceramic materials. The CAD-CAM ceramic specimens were randomly divided into two subgroups according to acid types: phosphoric (P) acid and hydrofluoric (HF) acid. Resin cement (Panavia V5; Kuraray, Japan) was applied using a 3 x 3-millimeter mold. All specimens were stored in distilled water at 37 degrees C for 24 hours. The SBS test was performed using a universal testing machine (0.5 mm/min). Two-way ANOVA was used to detect significant differences among the CAD-CAM ceramic materials and acid types. Subgroup analyses were conducted using Tukey HSD post-hoc test (p < 0.05). The lowest SBS value was seen in the VE group (4.5 +/- 2.2 MPa) for P acid etching. The highest SBS value was seen in the IPS group (19.5 +/- 8.3 MPa) for HF acid etching.