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Öğe Clinical factors affecting the translucency of monolithic Y-TZP ceramics(Springer, 2020) Pekkan, Gürel; Özcan, Mutlu; Subaşı, Meryem GülceThe use of monolithic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics in aesthetically critical regions is questionable because of the insufficient translucency and opacity of the restorations. Intrinsic (manufacturing process) and extrinsic factors (laboratory procedures and clinical factors) can affect the translucency of monolithic zirconia. In this narrative review, the clinical factors (thickness, cementation type, colour of the monolithic zirconia, surface finishing methods and wear, dental background, cement colour, low temperature degradation) affecting the translucency of monolithic Y-TZP ceramics were reported. © 2019, The Society of The Nippon Dental University.Öğe Effect of different sintering conditions on microstructural characterisation of Co-Cr metal laser powder(Inderscience Publishers, 2020) Pekkan, Gürel; Taşçı, Eda; Pekkan, Keriman; Ispalarlı, MuratCo-Cr alloys have been used for many years in dentistry. In recent years, the fabrication of prosthetic restorations from Co-Cr alloys by metal laser sintering method has become widespread. This method is a combination of powder metallurgy and three-dimensional printing technologies. The surface microstructure of the material and the different phases formed on the surface of the material after sintering and heat treatment are extremely important since these metal substructures are layered with dental porcelain in fixed prosthetic dentistry. In this study, characterisation of Co-Cr alloy samples produced by direct metal laser sintering (DMLS) method and sintering under various atmospheric conditions were performed with X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray diffractometer (EDX). It was observed that sintering with different methods under various atmospheric conditions affected the XRD phase intensities. The sintering in the argon gas atmosphere yielded a more significant phase separation that facilitates the identification of different phases in XRD patterns. Copyright © 2020 Inderscience Enterprises Ltd.Öğe Effect of micro blasting process parameters on 3D surface topography and surface properties of zirconia (Y-TZP) ceramics(Wiley, 2021) Yetik, Okan; Yavuzyeğit, Berzah; Yıldıran Avcu, Yasemin; Koçoğlu, Hurol; Pekkan, Gürel; Sarıdağ, Serkan; Avcu, EgemenThe present study aims to examine the effects of operational parameters on the surface topography and wear mechanisms of monolithic and conventional yttria-stabilized zirconia (Y-TZP) ceramics in the micro blasting process, performed under various acceleration pressures (1.5-3 bar), particle impact angles (30 degrees-90 degrees), and erodent particle sizes (50-460 mu m). Three-dimensional (3D) surface topography, surface roughness, and surface morphology of micro-blasted specimens were analyzed by using non-contact optical profilometry and SEM-EDS. The micro blasting characteristics of both Y-TZP were similar that increased blasting pressure and erodent particle size increased surface roughness. Erosion rate increased with increasing blasting pressure, whereas it decreased with increasing erodent particle size. Particle size was the most effective parameter on changing surface topography, while the particle impact angle had no distinct effect on the erosion rate, surface roughness, and surface topography of Y-TZP ceramics. SEM-EDS analyses showed that the primary wear mechanism during micro blasting was micro-cutting with a substantial amount of embedded particles on the material's surface.Öğe Evaluation of corrosion resistance of Co-Cr alloys fabricated with different metal laser sintering systems(Korean Academy of Prosthodontic, 2020) Tuna, Süleyman Hakan; Karaca, Erhan; Aslan, İsmail; Pekkan, Gürel; Özçiçek Pekmez, NuranPURPOSE. The aim of this study was to evaluate the corrosion resistance of the specimens produced by five different commercial metal laser sintering (MLS) systems with their recommended Co-Cr alloy powders. MATERIALS AND METHODS. The MLS machines and the alloy powders used were, ProX 100-ST2724G (St-Pro), Mysint 100-EOS SP2 (SP2-Mys), EOSINT 270-EOS SP2 (SP2-EOS), SLM 100-Starbond CoS (SB-SLM), and MLab Cusing-Remanium® Star (RS-MLab), respectively. Eight specimens from each group were prepared. Open circuit potential (Eocp) and electrochemical impedance spectroscopy (EIS) measurements of polished surfaces of the specimens were conducted in a three-electrode cell using a potentiostat-galvanostat in Fusayama-Meyer artificial saliva (AS). Specimens from each group were immersed in AS and de-ionized water for seven days. Eocp, charge transfer resistance (Rct) values, and released ions (?g/cm2 x 7d) in different solutions were determined. The specimen surfaces were observed with SEM/EDS. Results were analyzed statistically. RESULTS. Eocp values have shifted to potentials that are more positive over time. Steady-state Eocp values were from high to low as follows, SB-SLM, SP2-Mys, SP2-EOS, RS-MLab, and ST-Pro, respectively. After 60 mins, RS-MLab specimens had the highest Rct value, followed by SP2-Mys, SB-SLM, SP2-EOS, and ST-Pro. In all groups, ion release was higher in AS than that in de-ionized water. CONCLUSION. There were small differences among the corrosion resistances of the Co-Cr alloy specimens produced with MLS systems; meanwhile, the corrosion resistances were quite high for all specimens. © 2020 The Korean Academy of Prosthodontics.Öğe Evaluation of median mandibular flexure values in dentulous and edentulous subjects by using an intraoral digital scanner(Korean Acad Prosthodontics, 2022) Gülsoy, Merve; Tuna, Süleyman Hakan; Pekkan, GürelPURPOSE. Mandibular flexure is a crucial phenomenon that may affect the success of rigid bilateral mandibular prosthetic treatment. The aim of this study was to determine the amount of median mandibular flexure (MMF) that occurs during mouth opening from anterior to posterior mandible in seven different regions, in different age and gender groups of both dentulous and edentulous subjects, using an intraoral digital scanner. MATERIALS AND METHODS. In this study, the mandibular arch of 56 dentulous and 35 edentulous individuals were scanned with an intraoral scanner at both the minimum mouth opening (MnMO) and the maximum mouth opening (MxMO). MMF values were calculated by subtracting the distance value at the MxMO from the distance between the reference points at the MnMO at seven different mandibular regions of dentulous and edentulous subjects. In addition, the left and right side MMF values were measured. All data were analyzed statistically (alpha = .05). RESULTS. MMF value increased linearly from anterior to posterior mandible in both dentulous and edentulous individuals. The differences in MMF values were not statistically significant according to side (left/right), age, or gender (P > .05). No significant differences were found between the mean MMF values of the same region in both dentulous and edentulous individuals (P > .05). CONCLUSION. MMF was seen in different regions of the mandibles of both edentulous and dentulous individuals measured at the MxMO. Mandibular flexure should be considered for the success and prognosis of the long-span and rigid prostheses.Öğe Factors affecting the translucency of monolithic zirconia ceramics: A review from materials science perspective(Japanese Society for Dental Materials and Devices, 2020) Pekkan, Gürel; Pekkan, Keriman; Çukurluöz Bayındır, Banu; Özcan, Mutlu; Karasu, BekirThe use of monolithic [yttria (Y2O3)-stabilized tetragonal zirconia (ZrO2) polycrystalline] (Y-TZP) ceramics to restore teeth is expanding in dentistry. However, there are still some problems about color matching and the translucency of these ceramics. The employment of Y-TZP ceramics in aesthetically critical regions is questionable due to the insufficient translucency and opacity of the restorations. The objective of this review was to assess the factors affecting the translucency of monolithic Y-TZP ceramics for a better understanding the relevant parameters in restorations. The translucency of polycrystalline ceramics is a complex phenomenon. Apprehending the translucency regarding ceramics requires their knowledge of physical, chemical and microstructural characteristics with the light interactions among them. © 2020, Japanese Society for Dental Materials and Devices. All rights reserved.
