PubMed İndeksli Açık & Kapalı Erişimli Yayınlar
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Item Marginal fit of 3-unit CAD-CAM zirconia frameworks fabricated using cone beam computed tomography scans: an experimental study(2021) Belgin, Huseyin Berkay; Kale, Ediz; Ozcelik, Tuncer Burak; Yilmaz, Burak; 34665345Whether cone beam computed tomography (CBCT) scans can be used for the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) fixed dental prostheses (FDPs) is not known. The purpose of the present study was to compare the marginal fit of 3-unit zirconia FDPs fabricated by using CBCT or 3-dimensional (3D) laboratory scanning. Extracted second premolar and molar teeth in a maxillary typodont model were prepared. The first molar was removed and the typodont model was scanned with a laboratory or a CBCT scanner to generate two virtual 3D cast groups (3DL and CBCT). Forty four 3-unit zirconia FDPs were designed on virtual casts and milled. The vertical marginal discrepancy (VMD) was measured by x100-magnification microscopy at seven locations on each abutment. A total of 616 measurements were made at 14 fixed locations in two groups of 22 specimens. The VMD data for 3DL and CBCT groups were statistically analyzed using the Mann-Whitney U test (alpha = 0.05). The mean VMDs on premolar ranged between 44 and 55 mu m (median: 43-55 mu m) in 3DL, and 74 and 100 mu m (median: 72-93 mu m) in CBCT; and on the molar, between 47 and 114 mu m (median: 46-114 mu m) in 3DL, and 91 and 162 mu m (median: 93-156 mu m) in CBCT. There was a significant difference between the gaps in 3DL and CBCT groups (p < 0.001). FDPs fabricated using 3D laboratory scanner had significantly smaller VMDs. Nevertheless, the 3-unit zirconia FDPs fabricated using CBCT scans presented promising marginal integrity.Item Impact of multiple firings and resin cement type on shear bond strength between zirconia and resin cements(2020) Oguz, Ece Irem; Ozgur, Merve Erdog; Sungur, Sercan; Uctasli, Sadullah; 32879709PURPOSE. The aim of this study was to evaluate the effect of multiple firings on the bond strength between yttria-tetragonal zirconia polycrystals (Y-TZP) and 2 types of resin cements. MATERIALS AND METHODS. Sixty 3Y-TZP specimens (LAVA Frame Multi) were divided into 3 groups depending on the following firing procedures: (1) 2-firing cycles, (2) 5-firing cycles, (3) 10-firing cycles. Two samples from each group were investigated by using SEM to determine the morphological changes. All specimens were treated with 125 mu m airborne-particle abrasion and the surface roughness of each specimen was measured. The specimens from each firing group were then further divided into 2 subgroups (n = 9) to apply 2 types of resin cement (MDP-free resin cement: RelyX Unicem-RU, and MDP containing resin cement: Panavia F 2.0-PA). The shear bond strength (SBS) test was performed and failure types of all the debonded specimens were classified by using a stereomicroscope as adhesive, cohesive, and mixed. The statistical analysis of surface roughness and SBS data were performed by using 1-way ANOVA and 2-way ANOVA followed by Tukey-HSD tests (r=.05). Failure modes were calculated as a percentage for each group. RESULTS. The bond strength of RU and PA to the specimens obtained with 2 firings were not statistically different from each other (P=.1). However, the SBS values of PA were found to be significantly higher than RU for the specimens obtained with 5 and 10 firing cycles (P=.001 and respectively). Surface roughness analysis revealed no statistical difference between groups (P=.2). The SEM analysis of samples fired 5- and 10- times showed irregularities and boundary loss in zirconia grains, and empty spaces between zirconia grains. CONCLUSION. The bond strength of PA cement was higher than that of RU to the zirconia subjected to repeated firings (5 and 10 firing cycles). When zirconia is subjected to multiple firings, using MDP-containing resin cement can be recommended.