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  • Küçük Resim
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    The effect of ytterbium-doped fiber laser on titanium fused to ceramic
    (Uluslararası Diş Araştırmaları Birliği, 2021) Tepe, İbrahim Halil; Nigiz, Remzi; Polat, Zelal Seyfioğlu; Ünal, Server Mutluay
    Aim: The aim of our study is to compare the application of fiber lasers with aluminum oxide sandblasting and CoJet, which is one of the other surface roughening methods used for the first time in this study. Investigating the effect of titanium–porcelain bond strength is another aim of this study. Methodology: In total, 96 samples of titanium discs (6 mm in diameter and 3 mm in height) were prepared in a CAD/CAM device. Samples were divided into six groups (n: 10), including the control group, according to the applied surface treatments: one-way (horizontal) scanning with a Yb fiber laser, twoway (horizontal-vertical) scanning with a Yb fiber laser, three-way (horizontal–vertical–hypotenuse) scanning with a Yb fiber laser, CoJet, sandblasting, and the control group. After using the different surface treatments on the titanium discs, scanning electron microscope (SEM) imaging, a wettability test, and a profilometer test were applied to the samples in each group. After the surface treatments were applied to the titanium discs, including those in the control group, low heat porcelain (VITA Titanium Porcelain), which was 4 mm in diameter and 3 mm in height, was applied according to the manufacturer's instructions. Afterwards, porcelain samples prepared with titanium inlays were placed in acrylic blocks and kept in 37°C (±1°C) distilled water for 24 hours. Shear tests were applied to the samples embedded in prepared acrylic blocks, and the results were evaluated. Results: In the statistical evaluation of the obtained data, one-way analysis of variance (one-way ANOVA) was used to compare the statistical differences of the mean values of the bond strength between titanium and porcelain. In our study, Tukey’s HSD and Dunnett’s multiple comparison statistical tests were used to determine the differences among the groups. Conclusion: According to the results of our study, the highest average bond strength values were obtained from sandblasting and three-way fiber laser roughness. As a result, no statistically significant difference was found among the groups. Although Yb fiber laser application was not found to have a statistically significant effect on titanium porcelain bond strength, this method could be useful for titanium porcelain bonding.
  • Küçük Resim
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    Effects of crown retrieval on implants and the surrounding bone: A finite element analysis
    (Korean Academy of Prosthodontic, 2016) Özkir, Serhat Emre; Ünal, Server Mutluay; Yürekli, Emel; Güven, Sedat
    PURPOSE. The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS. Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant (3.7 mm × 10 mm) with a straight abutment, and the other model was designed as a 30-degree inclined implant (3.7 mm × 10 mm) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS. The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION. The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. Clinical implications . These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.
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    Evaluation of bond strength of different repair methods applied in PEEK infrastructure restorations
    (SCI Printers & Publication INC, 2022) Yılmaz, Berivan Dündar; Çetinkaya, Numan; Polat, Zelal Seyfioğlu; Ünal, Server Mutluay; Tuncer, Mehmet Cudi
    OBJECTIVE: To evaluate the appropriate intraoral repair procedures in PEEK (polyetheretherketone) restorations when there is a veneer fracture. STUDY DESIGN: The study groups were formed according to the presence or absence of fractured veneer material of PEEK restorations. PEEK specimens (N = 91) were prepared with CAD/CAM in dimensions of 5 x 5.4 x 13 mm and divided into 13 groups including the positive control group. 5000 thermocyclic was applied to the specimens, and then the repair bond strength (RBS) was made at a speed of 0.5 mm/min. The fracture surfaces of the specimens were examined under a stereomicroscope. SEM, EDX, XRD, AFM, and surface contact angle analyses were performed in terms of roughened surfaces of PEEK (N = 16). One-way ANOVA and independent sample t test were used for data analysis (alpha = 0.05). RESULTS: The efficiency of surface treatment, the roughness and wettability of the acid and Co-Jet groups have increased. Acid etching was found to be the most effective surface treatment. The RBS values of the Super-Bond groups in the repair procedures were found to be higher than the Visio.link group and were statistically significant (p = 0.002). When evaluating failure modes, the mode most encountered among all groups was the mixed mode, and least was the cohesive mode. CONCLUSION: The presence or absence of fractured veneer during the repair of PEEK-based restorations does not affect the values of repair bond strength, and RBS values were also not statistically significant.