Syfte: Syftet med föreliggande studie är att undersöka färgstabiliteten hos manuellt färginfiltrerad högtranslucent zirkonia efter upprepade bränningar.   Material och metod: Fem provkroppar av respektive fabrikat; Prettau® Zirconia (PZ) och M+W Zircon HT (MW) kapades fram ur ofärgade zirkonia-diskar. Provkropparna färgades in manuellt med färgen A3 och torkades därefter under en infraröd lampa. Provkropparna sintrades enligt fabrikanternas anvisningar och en första färgmätning utfördes med en spektrofotometer (VITA Easyshade Advance 4.0) mot en matt grå bakgrund. Där efter utfördes bränningar av provkropparna i fyra cykler. Efter varje cykel utfördes färgmätningar.Medelvärdena för L*a*b*c*h* registrerades. Formlerna CIE76 (∆E*ab) och CIEDE2000 (∆E*00) användes för att räkna ut färgskillnader efter bränncyklerna. Värdena registrerades i SPSS och analyserades med One-way ANOVA, Tukey’s test med en signifikansnivå på α=0,05.   Resultat: Statistiskt signifikanta skillnader (p<0,05) i färgförändring hittades både inom och mellan de båda grupperna (MW och PZ). Färgskillnaderna som uppmättes befann sig inom ramen för vad som anses som en acceptabel (∆E*ab≤2,7 och ∆E*00≤1,8) eller mycket god färgmatchning (∆E*ab≤1,2 och ∆E*00≤0,8).   Slutsats: Inom ramen för studiens begränsningar kan följande slutsatser dras: Upprepade bränningar påverkar färgen hos manuellt färginfiltrerad högtranslucent zirkonia. De färgförändringar som sker är inom ramen för vad som räknas som en ”acceptabel färgmatchning” eller ”mycket god färgmatchning” enligt aktuella gränsvärden. Färgförändringarna som sker är inte iögonfallande och har ringa betydelse kliniskt. Färgen och färgskillnader hos manuellt färginfiltrerad högtranslucent zirkonia är beroende av fabrikat. / Purpose: The purpose of this study is to investigate color stability in manually color infiltrated high translucent zirconia after repeated firings. Material and methods: Five specimens of each manufacturer; Prettau® Zirconia (PZ) and M+W Zircon HT (MW) were cut from uncolored zirconia discs. The specimens were manually colored with shade A3, and dried. The specimens were sintered and a first color measurement was performed with a spectrophotometer (VITA Easyshade Advance 4.0) against a matte gray background. Firings of the specimens were performed in four cycles. After each cycle, color measurements were performed. The mean values for L*a*b*c*h* ​​were registered. The formulas CIE76 (∆E*ab) and CIEDE2000 (∆E*00) were used to calculate color differences after firing cycles. The values were registered and analyzed with One-way ANOVA, Tukey's test with a level of significance at α=0.05.  Results: Statistically significant color differences (p<0.05) were found within and between groups (PZ and MW). The color differences measured were within the range of what is considered an acceptable match (∆E*ab≤2.7 and ∆E*00≤1.8) or a perfect match (∆E*ab≤1.2 and ∆E*00≤0.8).   Conclusion: Within the limitations of this study, the following conclusions can be drawn: Repeated firings affect the color in manually color infiltrated high translucent zirconia. The color changes that occur are within the range of what is considered an “acceptable match” or “perfect match” according to current thresholds. The color changes are not conspicuous and of little importance clinically. The color and color differences in manually color infiltrated high translucent zirconia are dependent on the brand.

SammanfattningSyfteSyftet med föreliggande pilotstudie är att undersöka abrasion på materialen polerad zirkonia (5YSZ) och glansbränd litiumdisilikat och abrasion på antagonist med eller utan termocykling. Emalj utgör referens. De inkluderade materialen är avsedda för CAD/CAM- framställning av monolitiska konstruktioner.Material och metodFrån en zirkoniadisk (5YSZ, Katana zirconia UTML) och tre litiumdisilikatblock (IPS e.max CAD LT) togs totalt sexton provkroppar fram. Åtta extraherade molarer användes som referensgrupp (n=8) och steatitkulor användes som antagonist. Provkropparna för zirkonia och litiumdisilikat utformades rektangulära med måtten 16x14x3,5 mm efter sintring respektive kristallisering. Provkropparnas testytor genomgick olika ytbehandlingar. Zirkoniaprovkropparna polerades till högglans (ZP), litiumdisilikat glansbrändes med glaze (LG) och de extraherade molarerna planslipades och emaljen polerades (EM). Hälften av materialgrupperna tuggsimulerades i 120 000 cyklar med termocykling i temperaturerna 15°C±2°C respektive 55°C±2°C (ZPT, LGT, EMT). Den andra hälften tuggsimulerades i 120 000 cyklar utan termocykling (ZPU, LGU, EMU). Resultaten analyserades med One-way ANOVA, Tukey’s test med en signifikansnivå på α=0,05 i statistikprogrammet SPSS.ResultatHögst materialförlust påvisades i EMT-gruppen och lägst i ZPU-gruppen. Ingen signifikant skillnad kunde påvisas mellan materialgrupperna. Hos antagonistgrupperna påvisade EMT- gruppen högst materialförlust och LGT-gruppen lägst materialförlust. Hos antagonistgrupperna hade EMT-gruppen en signifikant högre materialförlust i jämförelse med övriga antagonistgrupper förutom LGU- och ZPU-gruppen.SlutsatsPolerad ultratranslucent zirkonia, glansbränd litiumdisilikat, och emalj abraderas likvärdigt av antagonister med eller utan termocykling. Polerad ultratranslucent zirkonia och glansbränd litiumdisilikat abraderar mindre mot antagonister än emalj med termocykling. / AbstractPurposeThe purpose of this pilot study is to investigate the abrasion of polished zirconia (5YSZ) and glazed lithium disilicate on antagonist and antagonists’ abrasion on the materials with or without thermocycling, with enamel as reference. The materials are intended for CAD/CAM production of monolithic restorations.Material and methodFrom zirconia (5YSZ, Katana zirconia UTML) and lithium disilicate (IPS e.max CAD LT) sixteen specimens were made. Eight extracted molars were used as reference group (n=8) and steatite balls used as antagonists. The specimens were designed with the dimensions 16x14x3.5 mm. The zirconia specimens were polished to high gloss (ZP), the lithium disilicate glazed (LG) and the enamel ground flat and polished (EM). Half of the groups underwent chewing simulation in 120,000 cycles with thermocycling (15°C ±2°C/55°C ±2°C) (ZPT, LGT, EMT) and the other half without thermocycling (ZPU, LGU, EMU). The results were analyzed with One-way ANOVA, Tukey's test with a significance level of α= 0.05 in the statistical program SPSS.ResultsThe highest material loss was in EMT and the lowest in ZPU. No significant differences could be shown between the material groups. In the antagonist groups, EMT showed the highest material loss and LGT the lowest. In the antagonist groups, EMT had a significant higher loss in comparison with all the other antagonist groups except LGU and ZPU.ConclusionPolished ultratranslucent zirconia, glazed lithium disilicate and enamel are equally abraded by antagonists with or without thermocycling. Polished ultratranslucent zirconia and glazed lithium disilicate abrade less against antagonists than enamel with thermocycling.

BACKGROUND: Polymer-infiltrated zirconia ceramic, benefiting from the synergistic effect of the ceramic matrix providing strength and the polymer enhancing toughness, has the potential to mimic the structure of natural teeth in its optical and mechanical properties. OBJECTIVE: To determine the effect of additives and various sintering temperatures on the optical and mechanical properties of zirconia ceramic matrix composites. MATERIALS AND METHODS: Groups consisted of unmodified zirconia powder, and zirconia modified with porcelain and porogens to form the porous ceramic matrix. Three types of Tosoh zirconia powder, TZ-3YSB-E, Zpex, and Zpex Smile, were used to fabricate porous blocks. Zirconia powder and porcelain powder were ball-milled separately. Zirconia powder was dry pressed and then cold isostatic pressed. The blocks were sintered at 1000 and 1150 ºC and sectioned into discs (n=10). For zirconia with additives groups, 10% of Titankeramik and 5% of PEG8000 were mixed to zirconia powder using a high-speed mixer. The zirconia blocks were pressed and sintered at 1000, 1150, 1200 and 1300 ℃, and sectioned into discs (n=10). Porous discs were treated with a 10% wt solution of 10-MDP for 4 hours and then dried in a vacuum oven for 24 hours. TEGDMA-UDMA resin monomers were infiltrated into discs and cured at 90°C under pressure. Polymer-infiltrated ceramics specimens were polished to 1.5 mm in thickness. Optical properties were determined with an X-rite spectrophotometer. Biaxial flexural strength and Vickers indentation tests were performed using an Instron universal mechanical tester. Vickers hardness and indentation fracture toughness values were calculated by measuring the indent dimensions under FESEM, in addition to microstructure assessment. Statistical analyses were performed using computer software, Microsoft Excel 2016 and JMP Pro 15. RESULTS: This study revealed that the type of zirconia powder utilized for the fabrication of porous ceramics for polymer-infiltration structures did not significantly influence their optical properties. Mean values of fully sintered zirconia showed significantly higher biaxial flexural strength (628.5-1277.4 MPa) than polymer-infiltrated groups (105.4-433.6 MPa), with P-3Y1150 achieving the highest value. Higher pre-sintering temperature from 1000 ℃ to 1150 ℃ led to enhanced biaxial flexural strength for polymer-infiltrated pure zirconia specimens, with values rising from 126.5-158.2 MPa to 243.4-433.6 MPa. Adding porcelain and porogens did not significantly affect the optical or specific mechanical properties, such as biaxial flexural strength and Vickers hardness, despite increasing the sintering temperature to 1300 ℃. Nevertheless, a significant increase in indentation fracture toughness was noted with ZPTKPEG1200 (7.65±0.55 MPa·m1/2) and ZPTKPEG1300 (7.09±0.61 MPa·m1/2), values that were markedly higher than those in all control groups of fully sintered zirconia (p<0.001). Sintering temperature was found to be a key determinant in influencing the ceramic matrix's microstructure, porosity, and density, as well as the biaxial flexural strength, Vickers hardness, and indentation fracture toughness of polymer-infiltrated zirconia. While changes in temperature did not affect optical properties, and polymer infiltration did not enhance all attributes, it did substantially elevate the indentation fracture toughness in mixed zirconia samples with additives, offering a potential area for further research. CONCLUSION: The mechanical properties of polymer-infiltrated ceramics responded significantly to the sintering temperature and the type of zirconia powder utilized, most notably in the 3Y-TZSB-E group. A notable increased indentation fracture toughness was discernible when Zpex powder, mixed with additives, was subject to polymer infiltration and sintered at temperatures between 1200-1300 °C. Even though polymer infiltration and additive incorporation did not uniformly enhance all properties, a noticeable improvement in fracture toughness was observed. These findings open the door to future research, especially in potential applications of dental restorative materials that demand superior fracture toughness.

Background: The golden standard for single unit crowns has for long been porcelain fused to metal (PFM). However, demands for improved esthetic materials has driven the development of zirconia which has increased in popularity due to its eminent mechanical and esthetic properties. Long term follow-up of zirconia is lacking and no consensus regarding which luting agent to use has yet been established. Aim: The aim of the present study was to evaluate the longevity of single unit crowns in relation to luting cements used and to investigate if any shift in the choice of crown materials could be seen over time. Methods: A retrospective journal survey with inclusion criteria being patients treated with tooth supported single crowns at the students’ clinic at the Umea University School of Dentistry. Extracted data were focused on 8 factors regarding information about the patient and materials used in the crown treatment. Statistical analyses were made with GraphPad.com and Microsoft Excel 2010. Results: Core reinforced zirconia crowns luted with RelyX showed a statistically significant higher success rate (95%) compared to crowns luted with zinc oxide phosphate (60%) (p&lt;0.05). The most common complications were loss of retention and chipping of the veneering porcelain. Conclusion: The choice of luting agent seems to be of importance for core reinforced zirconia crowns. No statistically significant difference in success rate could be seen for PFM and monolithic zirconia. A shift in the choice of crown material could be seen. Monolithic ZR had increased, while PFM and ZR core had decreased.

Novel electrodeposition strategies have been developed for the fabrication of thick adherent zirconia ceramic and composite coatings for biomedical applications. The new method is based on the electrophoretic deposition (EPD) of polyelectrolyte additives combined with the cathodic precipitation of zirconia. The method enables the room- temperature electrosynthesis of crystalline zirconia nanoparticles in the polymer matrix. Adherent crack-free coatings up to several microns thick were obtained. The deposits were studied by thermogravimetric and differential thermal analysis, X-ray diffraction analysis, scanning and transmission electron microscopy, and atomic force microscopy. Obtained results pave the way for electrodeposition of other ceramic-polymer composites. Novel advanced nanocomposite coatings based on bioceramic hydroxyapatite (HA) have been developed for the surface modification of orthopaedic and dental implant metals. HA nanoparticles prepared by a chemical precipitation method were used for the fabrication of novel HA-chitosan nanocomposite coatings. The use of chitosan enables room-temperature fabrication of the composite coatings. The problems related to the sintering of HA can be avoided. A new electrodeposition strategy, based on the EPD of HA nanoparticles and electrochemical deposition of chitosan macromolecules, has been developed. The method enabled the formation of dense, adherent and uniform coatings of various thicknesses in the range of up to 60μm. Bioactive composite coatings containing 40.9-89.8 wt% HA were obtained. The deposit composition and microstructure can be tailored by varying the chitosan and HA concentrations in the deposition bath. A mathematical model describing the formation of the HA-chitosan composite deposit has been developed. X-ray studies revealed preferred orientation of HA nanoparticles in the nanocomposites. Obtained coatings provide corrosion protection of the substrates and can be utilized for the fabrication of advanced biomedical implants. For further functionalization of the HA-chitosan composite coating, Ag and CaSi03 have been incorporated into the coating. Novel HA-Ag-chitosan and HA-CaSiO3-chitosan nanocomposite coatings have been deposited as monolayers, laminates, and coatings of graded composition. The obtained results can be used for the development of biocompatible antimicrobial coatings with controlled Ag+ release rate, and nanocomposite coatings with enhanced bioactivity. / Thesis / Doctor of Philosophy (PhD)

<p> The stress relieving mechanisms in two different batches of thermal-shock resistant calcia-PSZ have been investigated. The nature of the stress relief in the two materials appears to result from the transformation of the pure ZrO₂ component of the microstructure at temperatures below, within, and above the normal transformation temperature range. In the batch #1 material, which contains a larger volume fraction of monoclinic phase, the cubic matrix material behaves in a "brittle" fashion resulting in the production of a high density of microcracks in the body. The density of these cracks is such that the level of energy that can be stored in the body is limited and thermal shock resistance results. The batch #2 material contains considerably less monoclinic material and the evidence suggests that the cubic matrix within it can act in a ductile fashion. This ductility together with the twinning of the monoclinic component of the microstructure possibly relieves the stresses developed in the material on thermal shock. </p> <p> In the batch #2 material, large platelets were observed to develop following thermal cycling from temperatures above those of the normal transformation. It has been demonstrated that stress plays a major role in the development of these features. In view of the possible ductility of the cubic matrix in this material it is suggested that the thermal cycling "works" the material, texturing the pure zirconia component in it, so leading to the development of the observed platelets. </p> / Thesis / Master of Engineering (ME)

Zirconium carbide (ZrC) is a high modulus ceramic with an ultra-high melting temperature and, consequently, is capable of withstanding extreme environments. Carbon-carbon composites (CCCs) are important structural materials in future hypersonic aircraft; however, these materials may be susceptible to degradation when exposed to elevated temperatures during extreme velocities. At speeds of exceeding Mach 5, intense heating of leading edges of the aircraft triggers rapid oxidation of carbon in CCCs resulting in degradation of the structure and probable failure. Environmental/thermal barrier coatings (EBC/TBC) are employed to protect airfoil structures from extreme conditions. Yttria stabilized zirconia (YSZ) is a well-known EBC/TBC material currently used to protect metallic turbine blades and other aerospace structures. In this work, 3 mol% YSZ has been studied as a potential EBC/TBC on CCCs. However, YSZ is an oxygen conductor and may not sufficiently slow the oxidation of the underlying CCC. Under appropriate conditions, ZrC can form at the interface between CCC and YSZ. Because ZrC is a poor oxygen ion conductor in addition to its stability at high temperatures, it can reduce the oxygen transport to the CCC and thus increase the service lifetime of the structure. This dissertation investigates the thermodynamics and kinetics of the YSZ/ZrC/CCC system and the resulting structural changes across multiple size scales. A series of experiments were conducted to understand the mechanisms and species involved in the carbothermal reduction of ZrO2 to form ZrC. 3 mol% YSZ and graphite powders were uniaxially pressed into pellets and reacted in a graphite (C) furnace. Rietveld x-ray diffraction phase quantification determined that greater fractions of ZrC were formed when carbon was the majority mobile species. These results were validated by modeling the process thermochemically and were confirmed with additional experiments. Measurements were conducted to examine the effect of carbothermal reduction on the bond lengths in YSZ and ZrC. Subsequent extended x-ray absorption fine structure (EXAFS) measurements and calculations showed Zr-O, Zr-C and Zr-Zr bond lengths to be unchanged after carbothermal reduction. Energy dispersive spectroscopy (EDS) line scan and mapping were carried out on carbothermaly reduced 3 mol% YSZ and 10 mol% YSZ powders. Results revealed Y2O3 stabilizer forming agglomerates with a very low solubility in ZrC.

OBJECTIVES: This study examined mechanical, chemical and microstructural properties of multilayer zirconia materials that are composed of layers of different forms of zirconia with varying translucency. Their resistance to low temperature degradation and their properties were compared to each other, and to monolithic zirconia. METHODOLOGY: “ZirCAD Prime” from Ivoclar Vivadent, “AxZir XT Multilayer Dental Zirconia” from Axsys Dental Solutions, and “inCoris ZI” from Dentsply Sirona, were examined. Twenty specimens were created from each material, half of which were aged. Specimens were examined for the following: Three point bending flexural strength, grain size, microhardness, indentation fracture toughness, warp and elemental composition. RESULTS: inCoris ZI had significantly higher flexural strength than ZirCAD Prime, which in turn had significantly higher strength than AxZir XT. The flexural strength values were 1113.55MPa, 857.21MPa and 625.77MPa, respectively. Grain size patterns were noted in multilayer specimens; more translucent layers had significantly larger grain sizes. AxZir XT’s incisal most layer average grain size was 0.988μm, whereas ZirCAD Prime’s was 1.172μm. The dentin most layer of AxZir XT average grain size was 0.529μm whereas ZirCAD Prime’s was 0.470μm. Microhardness results showed few significant differences between layers. The highest microhardness was found in AxZir XT’s incisal most layer, after aging, with a value of 13.502 GPa. The lowest was found in the aged inCoris ZI specimen, with a value of 10.775 GPa. In the ZirCAD Prime, fracture toughness was highest in the dentin most layer with a value of 8.88 MPa m¹/², compared to its incisal most layer that had a value of 4.92 MPa m¹/². This pattern was not seen in AxZir XT, where the dentin most layer had a value of 8.36 MPa m¹/², and the incisal most layer had a value of 6.40 MPa m¹/². Hydrothermal aging had detrimental and significant impacts on fracture toughness of all materials. Elemental composition analysis revealed predictable levels of elements or molecules in ZirCAD Prime. and inCoris ZI, but not within the AxZir XT. 5Y levels were seen in ZirCAD Prime’s incisal layer, and 2.5-3Y in the dentin most layer. inCoris ZI had constant levels of 3Y, but AxZir XT had no distinct level of Yttria in its layers. CONCLUSIONS: 1. Flexural Strength of multilayer materials was significantly lower than monolithic zirconia. 2. Grain sizes appeared largest in translucent incisal-most layers, with significant differences between them and the opaque dentin-most layers. 3. The elemental composition analysis showed an expected level of 3 mol% Yttria in the inCoris ZI with varying amounts by layer in the ZirCAD Prime from 3Y (cervical) to 5Y (incisal), but there was no clear gradation in the AxZir XT. 4. Some significant differences were seen between the materials and their layers in the microhardness tests. inCoris ZI had significantly lower values than both ZirCAD Prime and AxZir XT. The highest values were found within AxZir Xt. 5. Fracture toughness was significantly higher in the dentin-most layer compared to the incisal most-layer of ZirCAD Prime but not in AxZir XT. 6. LTD significantly decreased some fracture toughness test values. inCoris ZI, AxZir XT’s 1st incisal layer and ZirCAD Prime’s 2nd transition layer had significant decreases in fracture toughness after aging. 7. LTD had no impact on flexural strength or microhardness values. 8. LTD significantly decreased grain size of inCoris ZI.

Electrochemical conversion devices are a developing technology that prove to be a viable and more efficient alternative to current environmentally friendly generation devices. As such, constant research has been done in the last few decades to increase their applications and reliability. One of these systems, and the focus of this research, is the single cell Solid Oxide Fuel Cell (SOFC). These systems are a developing technology which main caveat is the need of high operating temperatures and costs. As such, most multidisciplinary research has been focused on researching materials and/or processes that help mitigate the costs or lower the operating temperature. The research presented in this paper focused on the manufacturing of a cubic stabilized zirconia (CSZ) electrolyte thin membrane for a single cell SOFC through tape casting. Thus, the process was divided into slurry preparation, tape casting, further processing, and analysis of samples. First the tape was produced reaching optimal viscosity (between 500 to 6000 cP) and minimizing impurities. Then, the slurry was poured into the doctor's blade with a 200 micrometers gap and allowed to dry. Samples were punched from the green tape with a diameter of 28 inches. Afterwards, these samples were pressed and sintered with a force of 218016 N and temperature of 1550 degrees celsius, respectively. These steps are done to maximize density and grain growth and minimize porosity. Lastly, the tape went further analysis and it was stated that further research should be done to determine this tape viability for stationary SOFC application.

Cerium and zirconium oxides are important materials in industrial catalysis. Particularly, the great advances attained in the past 30 years in controlling levels of gaseous pollutants released from internal combustion engines can be attributed to the development of catalysts employing these materials. Unfortunately, oxides of sulfur are known threats to the longevity of many catalytic systems by irreversibly interacting with catalytic materials over some time period. In this work, polycrystalline cerium-zirconium mixed-metal-oxide (MMO) solid solutions of various molar ratios were synthesized. High resolution x-ray photoelectron spectroscopy (XPS) was used to characterize the model system. The spectral data was examined for revelation of the surface species that form on these metal oxides after insitu exposures to sulfur dioxide at various temperatures. The model catalysts were exposed to sulfur dioxide using a custom modified in-situ reaction cell. A reliable sample platen heater was designed and built to allow the exposure of the model system at temperatures up to 673 K. The results of this study demonstrate the formation of sulfate and sulfite adsorbed sulfur species. Temperature and compositional dependencies were displayed, with higher temperatures and ceria molar ratios displaying a larger propensity for forming surface sulfur species. In addition to analysis of sulfur photoemission, the photoemission regions of oxygen, zirconium, and cerium were examined for the materials used in this study before and after the aforementioned treatments with sulfur dioxide. The presence of surface hydroxyl groups was observed and metal oxidation state changes were probed to further enhance the understanding of sulfur dioxide adsorption on the synthesized materials. Palladium loaded mixed-metal oxides were synthesized using a unique solid-state methodology to probe the effect of palladium addition on sulfur dioxide adsorption. Microscopic characterization of the wafers made using palladium-loaded MMO materials provide justification for using this material preparation method in surface science studies. The addition of palladium to this model system is shown to have a strong effect on the magnitude of adsorption for sulfur dioxide on some material/exposure condition combinations. Ceria/zirconia sulfite and sulfate species are identified on the palladium-loaded MMO materials with adsorption sites located on the exposed oxide sites.