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Objectives This study aimed to evaluate the optical properties of highly translucent 5 mol% yttria, partially stabilised monolithic zirconia, and 3 mol% yttria-stabilised tetragonal zirconia after their subjection to different milling methods and artificial ageing. Methods Two types of pre-shaded zirconia materials were used: inCoris TZI C and Katana STML. A total of 120 specimens were categorised according to the milling method (dry or wet-milling) and the solution used for milling (fresh distilled water or impregnated water with residues of CAD/CAM ceramic materials). The translucency and contrast ratios of all specimens were calculated after they were subjected to sintering and accelerated ageing. The material phase composition was tested before and after ageing, using X-ray diffraction analysis to evaluate T-M phase transformation. Data were statistically analysed via a three-way analysis of variance between the subject factors, the material and milling method, and the within-subject factor, ageing. The analysis of covariance model was used to analyse the changes in translucency and contrast ratio between baseline and ageing, with statistical significance set at p Results Katana STML and inCoris TZI C showed the highest translucency when dry-milled (21.9 ± 1.4, and 11.8 ± 0.7, respectively), and the lowest when milled with used impregnated water (5.4 ± 1.2 and 10.7 ± 1.3, respectively). Wet-milling using impregnated water, should be avoided owing to the saturation of alumina particles. Accelerated ageing resulted in the same pattern for both materials. Significance Dry milling of highly translucent zirconia can result in higher translucency and lower contrast ratio values.

Objectives The aim of this laboratory study was to evaluate the wear resistance of crowns made from current computer-aided design and computer-aided manufacture (CAD/CAM) materials. In addition, the abrasion of the steatite antagonist against these materials was compared. Methods Identically shaped crowns of lithium disilicate, zirconia-reinforced lithium disilicate and a polymer-infiltrated ceramic network (PICN) were fabricated with an occlusal thickness of 1.5 mm and a lateral wall thickness of 1.2 mm (n = 8). The crowns were cemented with a dual-polymerizing luting resin on composite resin dies. Using spherical steatite antagonists, all specimens were loaded with 49 N for 1,200,000 cycles in a mastication simulator with additional thermocycling. After 120,000, 240,000, 480,000, 960,000, and 1,200,000 cycles, precision impressions were made and investigated with a laser scanning microscope. The vertical and volume substance loss was measured. Additionally, the substance loss of the antagonists was evaluated after 1,200,000 loading cycles. Results No significant difference (p > 0.05) was found in the median volume loss of the test materials after 1,200,000 cycles (lithium disilicate: 0.405 mm3, PICN: 0.362 mm3, zirconia-reinforced lithium disilicate: 0.340 mm3). The vertical substance loss of PICN (157 μm) was significantly lower (p ≤ 0.05) than that of lithium disilicate (201 μm) and zirconia reinforced lithium disilicate (191 μm). However, the substance loss of steatite against zirconia-reinforced lithium disilicate (0.191 mm3) was significantly lower (p ≤ 0.05) than against lithium disilicate (0.296 mm3) and PICN (0.531 mm3). Significance All three CAD/CAM materials showed wear resistance that seems appropriate for clinical application. Also, the abrasion of the antagonist looks promising.

Objective This study evaluated the effect of dwell time (conventional or extended) and cooling protocol (fast or slow) of self-glaze firings on the mechanical (flexural strength and crack propagation) and optical (color and translucency) properties of a porcelain-veneered zirconia system. Methods Bilayer disc-shaped samples were prepared (Vita VM9 + In-Ceram YZ) and divided according to the final thermal treatment: glaze firing followed by slow cooling (furnace opening at 200 °C) (G-S) or fast cooling (furnace opening at 600 °C) (G-F, manufacturer-recommended protocol), extended glaze firing (15 min of dwell time) followed by slow cooling (EG-S) or fast cooling (EG-F), or no thermal treatment (CTRL). Porcelain roughness (Ra and Rz) was measured before and after glaze firings. Color (ΔE00) and translucency (TP00) alteration were also evaluated. Flexural strength was measured with the piston-on-three-ball test and crack propagation analysis was performed after Vickers indentations. Complementary analyzes of crystalline phase and scanning electron microscopy were carried out. Results Significant effect of dwell time was observed, with extended glaze leading to higher flexural strength and shorter crack lengths. Cracks of EG groups were observed to end in clusters of crystals. Color and translucency changed below perceptibility thresholds. All treatments led to a smoother surface and EG groups reached the lowest Rz values. An extra SiO2 peak was revealed in control and EG groups. No effect of cooling protocol was found. Significance Extended glaze firing was able to improve the resistance to crack initiation and propagation of porcelain-veneered zirconia without clinically perceptible changes in optical properties.

The purpose of this laboratory study is to evaluate the application of a pre-sintered surface augmentation to zirconia (Zir) and lithium disilicate (LDS) ceramics on the delamination strength of adhesive resin cement. The applied surface augmentation was the ruling of lines to the pre-sintered surface of the ceramics.Ninety milled Zir and sixty pressed LDS specimens (3mm×0.5mm×25mm) were created and divided into five groups (n=30). Group 1: Zir no surface treatment (control Zir-NT); Group 2: Zir airborne particle abraded (Zir-APA) with 30μm CoJet; Group 3: Zir pre-sintered surface augmentation (Zir-SA); Group 4: LDS etched (control LDS-etched) and; Group 5: LDS with pre-sintered surface augmentation and etching (LDS-SA). A resin adhesive cement (3mm×1mm×8mm) was then applied and cured to the ceramic specimens. The delamination strength values of the resin cement from the ceramic were recorded. The delamination strength data were analysed statistically using one-way ANOVA and Turkey post hoc analysis.The mean delamination strength and standard deviation, when comparing only the Zir-SA to the resin cement were statistically different (p0.001); Zir-SA 63.42±11.85, Zir-NT 26.82±12.07, and Zir-APA 48.11±17.85MPa. Comparison between LDS groups were not significantly different (p=0.193); LDS-etched 33.49±16.07 and LDS-SA 28.83±10.15MPa. The delaminated Weibull modulus was highest for surface augmentation Zir specimens (m=13.56) but decreasing to less than half for Zir-APA (m=6.27) and Zir-NT (m=5.68). The Weibull values for the LDS-SA and LDS-etched specimens was 5.63 and 3.38 respectively.Incorporating the pre-sintered surface augmentation to zirconia improved the delamination strength and reliability of Zir to the resin cement but not for LDS.

Objectives To evaluate the effect of laser fused and air abraded fluorapatite particles on flexural strength σ f and fracture toughness (KIC) of Yttria tetragonal zirconia polycrystal (Y-TZP). Methods 160 polished Y-TZP bars received one of the following surface treatments: airborne particle abrasion (APA) with fluorapatite glass-ceramics (FGC), APA with tribochemical silica-coated alumina (CoJet), laser fused FGC using Nd:YAG Laser (FGC + Laser), while as-sintered polished specimens served as control. Initial flexural strength σ f I was measured to half of the specimens, while the rest underwent cyclic fatigue (1,000,000 cycle of 15N load and 3 s contact time) followed by measuring residual flexural strength σ f R . Fractographic analysis was performed and KIC was calculated. The effect of surface treatment and fatigue on flexural strength was statistically analysed using 2-way ANOVA (α = 0.05). Weibull probability was measured to assess the reliability of flexural strength. Results The highest σ f before or after the fatigue was reported for the control group while the lowest was for FGC + Laser group. Cyclic fatigue significantly decreased the flexural strength of all groups except for FGC + Laser group. There was no significant difference between the KIC between the control and FGC groups, however, a significant reduction of KIC was found in the CoJet group, while FGC + Laser reported the significant lowest value compared to all groups (P = 0.00). Significance Fluorapatite glass-ceramic powder offers a promising alternative for particle abrasion of zirconia-based frameworks.

Made available in DSpace on 2021-06-25T10:55:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Objective: Continuous efforts have been made to hasten the zirconia densification process without compromising properties. This study evaluated the long-term structural durability of microwave speed-sintered zirconia (MWZ) relative to a conventionally sintered zirconia (CZ). Methods: As-machined dental 3Y-TZP discs (Ø12 × 1.2 mm) were speed sintered at 1450 °C for 15 min using an industrial microwave oven, while conventional sintering was conducted in a standard dental furnace at 1530 °C for 2 h. Both were followed by natural cooling. The total sintering time was 105 min for MWZ and 600 min for CZ. Groups were compared regarding density, grain size, phase composition, and fracture resistance. Structural durability was investigated employing two fatigue protocols, step-stress and dynamic fatigue. Results: Compared to CZ, MWZ exhibited a slightly lower density (MWZ = 5.98 g/cm3, CZ = 6.03 g/cm3), but significantly smaller grain sizes (MWZ = 0.53 ± 0.09 μm, CZ = 0.89 ± 0.10 μm), lower cubic-zirconia contents (MWZ = 15.3%, CZ = 22.7%), and poorer translucency properties (TP) (MWZ = 13 ± 1, CZ = 29 ± 0.8). However, the two materials showed similar flexural strength (MWZ = 978 ± 112 MPa, CZ = 1044 ± 161 MPa). Additionally, step-stress testing failed to capture the fatigue effect in 3Y-TZP, whereas dynamic fatigue revealed structural degradation due to moisture-assisted slow-crack-growth (SCG). Finally, MWZ possessed a slightly higher Weibull modulus (MWZ = 7.9, CZ = 6.7) but similar resistance to SCG (MWZ = 27.5, CZ = 24.1) relative to CZ. Significance: Dental 3Y-TZP with similar structural durability can be fabricated six-times faster by microwave than conventional sintering. Department of Dental Materials and Prosthodontics Institute of Science and Technology of Sao Jose dos Campos Sao Paulo State University (UNESP), 777 Eng. Francisco Jose Longo Avenue Graduate Program in Dentistry Positivo University Department of Biomaterials and Biomimetics New York University College of Dentistry, 433 1st Ave. Department of Preventive and Restorative Sciences University of Pennsylvanian School of Dental Medicine, 240 S. 40th St. Department of Dental Materials and Prosthodontics Institute of Science and Technology of Sao Jose dos Campos Sao Paulo State University (UNESP), 777 Eng. Francisco Jose Longo Avenue

Objectives The aim of this study is to improve the biological and mechanical properties of zirconia-based PICN (polymer-infiltrated-ceramic-network) materials by fabrication an enamel-like structure on its surface. Methods Fluorapatite (FA) arrays were fabricated on zirconia discs by hydrothermal treatment. After polymer infiltration, an enamel-like structure was obtained on zirconia-based PICN materials. Effects of hydrothermal treatment conditions on the FA arrays were investigated by XRD, FTIR and SEM. Human gingival fibroblast cells (HGFs) and Escherichia coli (E. coli) were used to evaluate the cytocompatibility and antibacterial properties. Nanoindentation method was employed to determine elastic modulus and hardness. Results A facile and pervasive method was developed in this study to fabricate an enamel-like structure constituted of controlled FA arrays and interstitial resin on zirconia-based PICN materials. The obtained FA arrays can significantly promote the adhesion and proliferation of human gingival fibroblasts (HGFs), and further effectively inhibit the growth of Escherichia coli. Owing to the hierarchical structure, the enamel-like structure has achieved a hardness of 1.79 GPa and a lower Young’s modulus of 37.4 GPa. Significances The enamel-like structure, with excellent biological and mechanical properties, is promising for various applications in dentistry.

Objective In vivo aging of biomedical grade 3Y-TZP ceramics in the oral environment was assessed and compared to artificially accelerated in vitro hydrothermal aging extrapolations at 37 °C. Methods 88 discs were pressed and sintered (1450–1500 °C) from two commercial 3Y-TZP compositions containing 0.25% Al2O3 to generate finer- and coarser-grained specimens. As-sintered (AS) and airborne-particle abraded (APA; 50 μm Al2O3) surfaces were investigated. In vivo aging was performed by incorporating specimens in lingual flanges of complete dentures of 12 edentulous volunteers who wore them continuously for up to 24 months. For comparison, in vitro hydrothermal aging at 134 °C was also performed and analysed by XRD and (FIB)-SEM. Data was statistically analysed with linear regression models. Results Finer and coarser-grained specimens exhibited statistically insignificant differences in aging in vivo. The monoclinic fraction (Xm) on AS surfaces abruptly increased to ∼8% after 6 months. The aging process then proceeded with slower linear kinetics (∼0.24%/month). After 24 months, Xm reached ∼12%. The calculated maximum transformed layer was 0.385 μm representing one layer of transformed grains. APA surfaces were highly aging resistant. The initial Xm of ∼4.0% linearly increased by 0.03%/month in vivo. In vitro aging exhibited an initial induction period, followed by linear aging kinetics. Coarser-grained AS surfaces aged significantly faster than fine-grained (2.41%/h compared to 2.16%/h). APA discs aged at a rate of 0.3%/h in vitro. Microcracking within a single grain and pull-out of grain clusters were observed on aged AS surfaces. Significance Biomedical grade 3Y-TZP was susceptible to in vivo aging. After 2 years in vivo, the aging kinetics were almost 3-times faster than the generally accepted in vitro-in vivo extrapolation.

Made available in DSpace on 2021-06-25T11:08:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Objective: Despite the increased use of monolithic crowns, their performance has yet to be determined when the minimal tooth preparation (MTP) principle is considered. The goal of this study was to evaluate the effect of MTP on the mechanical behavior, reliability and translucency of posterior monolithic ceramic crowns. Methods: Dentin analogues were machined using two preparation designs (0.5 or 1 mm reduction) to receive first molar crowns in order to evaluate the monolithic crown performance. Next, 126 crowns were divided (21/g) according to the material (High translucent zirconia – YZHT, Zirconia reinforced lithium silicate – ZLS and Hybrid ceramic – HC) and thickness (0.5 or 1 mm). Tensile stress concentration was calculated using the finite element method. The crowns were adhesivelly cemented and step stress fatigued to calculate reliability for missions at 600 and 1000 N. Translucency was analyzed in 10 discs of each material and thickness. Results: Higher stress concentration was found in thinner crowns and those with higher elastic modulus. YZHT crowns were suspended when fatigue reached 1500 N load, thus 1-parameter Weibull was used to analyze the data. Reliability was only affected by thickness at 1000 N. ZLS.5 showed lower survival than HC.5, which was similar to the groups that presented 100% survival. YZHT showed the highest strength and data scattering. ZLS1 (22.3 ± 1.4) presented higher translucency than HC1 (19.2 ± 0.6) and YZHT1 (12.0 ± 2.9), whereas ZLS.5 and HC.5 were similar to each other (26.5 ± 2.3, 26.7 ± 2.2) and superior to YZHT.5 (12.7 ± 1.2). Significance: HC.5 combined high reliability and translucency with low stress concentration, yielding better crown performance and tooth preservation. PhD Graduate Program in Restorative Dentistry São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, nº 777, Jardim São Dimas Department of Prosthodontics and Periodontology University of São Paulo – Bauru School of Dentistry, Alameda Dr. Octávio Pinheiro Brisolla, 9-75 PhD Graduate Program in Restorative Dentistry São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, nº 777, Jardim São Dimas FAPESP: #2012/19078-7 FAPESP: #2017/09104-4 FAPESP: #2017/11535-3 FAPESP: #2017/23059-1 FAPESP: #2018/03072-6 FAPESP: #2018/03984-5

Objective Mechanical damages can occur from dental restoration processing and fitting, or while it is in-service. This study evaluates the damage sensitivity of translucent zirconia (5Y-PSZ) relative to conventional 3Y-PSZ following mouth-motion simulations at various loads. Methods 5Y-PSZ and 3Y-PSZ discs were adhesively bonded to a dentin-like substrate and divided into groups according to the load (50 N or 200 N) and number of cycles (up to 106) used in the chewing simulation. Specimens were mounted with 30° inclination in an electrodynamic mouth-motion simulator, and subjected to contact-slide-liftoff cyclic loading in water. Surface and sub-surface damages were analyzed using a sectioning technique. After the simulation, specimens were removed from the substrate and loaded with the damaged surface in tension for biaxial strength testing to assess their damage tolerance. Results The strength of both ceramics underwent significant degradation after mouth-motion simulations. For 5Y-PSZ, the strength degradation was greater (∼60%) and occurred at a lower number of cycles than 3Y-PSZ. Herringbone cracks emerged on 3Y-PSZ and 5Y-PSZ surfaces under a 200-N load after 50 and 10 cycles, respectively. Meanwhile at a 50-N load, cracks formed at ∼1000 cycles in both ceramics. Further increasing the number of cycles only had moderate effects on the strength of both ceramics, despite an increase in surface and sub-surface damage. More significantly, a 50-N occlusal load can debase the zirconia strengths as much as a 200-N load. Significance Surface flaws produced during the chewing simulation are capable of significant strength degradation in zirconia, even after a small number of low-load cycles.

Objective To determine the Weibull modulus m , the characteristic strength σ 0 ,the subcritical crack growth (SCG) parameters ( n & A * ) as well as the lifetime durability of three dental ceramic materials in water: a polycrystalline yttria-stabilized zirconia (Zenostar MT O, YSZ, Ivoclar Vivadent/Wieland, Germany), a lithium disilicate glass ceramic (IPS e.max CAD, LD, Ivoclar Vivadent, Liechtenstein), and a zirconia-containing lithium silicate glass ceramic (Celtra Duo, ZLS, Dentsply Sirona Inc, USA). Methods 30 specimens (O12 mm × 0.9 mm thickness) of each material were fabricated. The biaxial ring-on-ring bending tests at four stress rates σ ˙ (100, 10, 1, 0.1 MPa/s) were performed in water for all three ceramics. The results were used to determine the Weibull and SCG parameters, and to plot the Strength-Probability-Time (SPT) diagram. Results YSZ showed the highest m (12.5) and highest σ 0 (542 MPa), while the values for the glass ceramic materials were lower: for LD m = 4.7, σ 0 = 407 MPa, and for ZLS m = 2.7, σ 0 = 279 MPa. The n for YSZ, LD and ZLS in water were 31.1, 13.7 and 16.6, respectively. The strength of YSZ decreased by 50% within a simulated period of 10 years, and for the glass ceramic materials the decrease was up to 80%. Significance Determining the Weibull and SCG parameters from the constant stress rate testing is an efficient methodology for ranking materials in terms of durability and longevity.

Objective The aims of this study were: 1) to evaluate the effect of sintering temperature on microstructure, density and flexural strength of a 3Y-TZP/TiO2 composite containing 12.5 wt% of TiO2 compared to 3Y-TZP specimens (control); 2) to compare 3Y-TZP with the experimental 3Y-TZP/TiO2 composite, both sintered at 1400 °C, with respect to the following parameters: optical properties, characteristic strength, Weibull modulus, fatigue behavior, induction of osteoblasts proliferation and differentiation (mineralization nodules formation). Methods The 3Y-TZP and 3Y-TZP/TiO2 powders were uniaxially pressed and sintered at 1200 °C, 1300 °C, 1400 °C or 1500 °C for one hour in a furnace. The microstructural analysis consisted of X-ray diffraction and scanning electron microscopy. The density was measured by the Archimedes' principle and the flexural strength was obtained by the biaxial flexure test. The optical properties were measured using a spectrophotometer operating in the visible light wavelength range. The step-stress accelerated life testing was performed by the pneumatic mechanical cycler and the biological behavior achieved by using osteoblast-like cells (Osteo-1 cell line). Results Tetragonal zirconia was identified in all groups and cubic zirconia was identified only at 3Y-TZP group. The addition of TiO2 decreased the values of density and flexural strength of the composite 3Y-TZP/TiO2 in relation to 3Y-TZP regardless of the sintering temperature. The color difference between the two materials was not significant regarding L*a*b* parameters. The composite showed higher probability of failure, and induced higher proliferation and differentiation than control. Significance The composite developed have good aesthetic and biologics properties. However, its microstructure and mechanical properties need to be improved for future dental implant applications.

Objective Zirconia and alumina nanoparticles were coated with a silica-rich layer (ALSI and ZRSI) and used to prepare experimental nanohybrid resin composites, which were characterized and compared to a control commercial resin composite (Filtek Z350 XT). Methods Silica nanoparticles with sizes compatible to ALSI (Aerosil 150) and ZRSI (Aerosil OX 50) were tested as references. The volume of nanoparticles was equivalent across the composites, which also had consistent content of glass microparticles. C C conversion, viscosity, depth of cure, surface topography, hardness, opacity, radio-opacity, and edge chipping resistance (ReA) were tested after 24 h. Flexural strength (σf) and fracture toughness (KIC) were also tested after 15 K thermal cycles. Data were analyzed using one-way or two-way ANOVA and Tukey’s test (α = 0.05). Results ALSI and ZRSI yielded resin composites with lower viscosity and more irregular nanoagglomerates compared to nanosilica-based composites. C C conversion and depth of cure were lower for ZRSI composite, which had higher opacity, radio-opacity, and hardness. ReA was higher for ALSI composite. Composites with ALSI and ZRSI showed stable σf after aging, whereas the control and Aerosil 150 resin composites showed significant degradation. The commercial and nanosilica-based composites showed up to 42% reduction in KIC after aging, whereas resin composites with ZRSI and ALSI showed a more stable KIC. Significance ALSI and ZRSI generated nanohybrid resin composites with improved and/or more stable physical properties compared with nanosilica-based and commercial composites. This study suggests that changing the composition of nanofillers is a simple method to enhance the performance of nanohybrid composites.

Objectives Different approaches are currently undertaken to structure the endosseous part of zirconia implants. The purpose of the present study was to evaluate how surface roughness and monoclinic to tetragonal phase ratio of zirconia affect cell behavior of human osteoblasts. Methods Zirconia discs with five different surface structures were produced: machined; machined heat-treated; polished; polished heat-treated; sandblasted, etched and heat-treated (cer.face 14, vitaclinical). The specimen surfaces were then characterized in terms of monoclinic to tetragonal phase ratio, wettability, roughness and visualized using scanning electron microscopy. To determine the reaction of the human osteoblastic cells (MG-63) to the surface roughness and monoclinic to tetragonal phase ratio of zirconia, cell spreading, morphology, actin cytoskeleton, viability and gene expression of alkaline phosphatase (ALP), collagen type I (COL) and osteocalcin (OCN) were assessed. Results Heat-treatment of the specimens significantly improved the surface wettability. With increased surface roughness Ra of the specimens, cell spreading was reduced. Cell viability after 24 h correlated linearly with the tetragonal phase ratio of the specimens. Gene expression after 24 h and 3 d was comparable on all specimens irrespective their surface roughness or monoclinic to tetragonal phase ratio. Significance Smooth zirconia surfaces with a high tetragonal phase ratio revealed best surface conditions for MG-63 osteoblastic cells and may be considered to design the endosseous part of zirconia implants.

Objective The neck area of zirconia implants or abutments is currently either machined, polished and in some cases additionally heat-treated. The aim of the present study was to determine how the surface topography and crystalline structure of zirconia affects the viability of human gingival fibroblasts (HGF-1). Methods Zirconia discs with a diameter of 13 mm were either polished [Zp], polished and heat-treated [Zpt], machined [Zm], machined and heat-treated [Zmt] or sandblasted, etched and heat-treated [Z14] which is the surface topography of the endosseous part of a zirconia implant. The specimen surfaces were analyzed using scanning electron microscopy (SEM), characterized in terms of monoclinic to tetragonal phase ratio, storage effect on wettability and roughness. The viability and morphology of HGF-1 cells was then tested on all surfaces after 24 h. Results The effect of the heat-treatment was visualized for the polished specimens with SEM. Contact angle of water was significantly decreased after 2 weeks air storage of the zirconia. Cell viability was significantly higher on smooth surfaces (Zpt, Zm, Zmt) when compared to Z14. HGF-1 cells spread very flat and attached tightly to the smoother surfaces Zp, Zpt, Zm and Zmt while on Z14, cells did not fully extend into the etched morphology of zirconia and stretched over longer distances. Significance For the structuring of the neck part of zirconia implants or abutments, a smooth surface with exposed grains might be suggested as the optimal substrate for human gingival fibroblasts. The wettability with water of zirconia decreases with prolonged air storage.

Objective Most previous work conducted on the wear behavior of dental materials has focused on wear rates and surface damage. There is, however, scarce information regarding the subsurface damage arising from sliding contact fatigue. The aim of this study was to elucidate the wear mechanisms and the subsurface damage generated during sliding contact fatigue in 5 contemporary CAD/CAM materials against a zirconia indenter. Methods Forty discs (O12 mm, 1.55 mm thick) were cut out of IPS e.max CAD (e.CAD), Suprinity PC (SUP), Enamic (ENA), Vitablocs Mark II (VMII) and Lava Ultimate (LU) blocks and mirror polished. After cementation onto a dentin-like composite, off-axis mouth-motion cycling was conducted with a spherical zirconia indenter (r = 3.18 mm) in water (200 N load, 2 Hz frequency) for 5 different cycling periods (102, 103, 104, 105, 106 cycles, n = 8). Analysis of the wear scars was conducted using light-microscopy, scanning-electron-microscopy and optical profilometry. Subsurface damage was assessed using sagittal and transverse sections of the samples. Results Fatigue wear mechanisms predominated in glassy materials (e.CAD, SUP, VMII), accompanied by extensive subsurface damage, whereas abrasive wear mechanisms were responsible for the large wear craters in the resin composite (LU) with an absolute absence of subsurface fracture. A combination of both mechanisms was observed in the polymer-infiltrated reinforced-glass (ENA), displaying large wear craters and severe subsurface damage. Significance Well-controlled laboratory simulation can identify wear and subsurface damage susceptibility of various classes of restorative materials. Both wear and subsurface fracture are determining factors for the long-term success of restorations.

Objective The main goal of this review is to provide an in-depth description of published work on the application of zirconia for dental implansts and restorations on titanium implants, with an emphasis on clinical studies from the past dozen years with at least 1-year follow-up. Methods Online databases (Pubmed, Science Direct, Web of Science) were consulted on this topic. Published work from 2007 to 2019 was collected, analyzed and pertinent articles were selected for inclusion on this review. Results No clear superiority has been documented in biocompatibility, osteoconductivity, physical properties or allergenicity with zirconia implants compared to titanium, notwithstanding an esthetic benefit. While short-term studies have been promising, larger multicentered, longitudinal and randomized clinical trials with success data are required to validate zirconia as a viable alternative to the titanium implant and its design. Zirconia abutments with a titanium base have revealed a high survival rate and show no difference to metal. Bi-layered zirconia ceramic restorations are a valid treatment alternative to metal ceramic implant restorations for single crowns with similar biological complications and enhanced esthetics. Monolithic zirconia restorations hold promise to address the chipping incidence of the bi-layered ceramic restoration, but longer-term studies are necessary, and work needs to be done to improve their esthetics. The gingival feldspathic porcelain veneered monolithic zirconia complete arch prosthesis versus a resin metal prosthesis, in medium-term studies, offers a high survival rate and low mechanical complication rate, reduced laboratory costs, superior durability and wear characteristics, enhanced fit due to digital fabrication, availability of a digital file for duplication in the future, acrylic try-for adjustment and approval, and reduced plaque and biofilm accumulation. Significance Zirconia is a versatile material for implant prosthodontic application. Longer-term multi-centered studies are needed to assess success criteria and patient-related outcomes measurements. Monolithic zirconia offers enhanced mechanical properties for implant restorations, but development is needed to optimize esthetics.

Made available in DSpace on 2020-12-12T00:55:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-01 Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) National Institute of Dental and Craniofacial Research Objective: To evaluate the influence of extrinsic pigmentation on the biaxial flexural strength and surface topographic of translucent Y-TZP (InCoris TZI – Sirona – USA) subjected to several surface treatments. Methods: Sintered zirconia discs-shaped specimens (n = 120) (ø:12 mm; thickness:1.2 mm; ISO 6872) were prepared and divided (n = 15) according to various factors: “extrinsic pigmentation” (n: without; p: with) and “surface treatments” (C: control — as sintered; A: abraded with silica-coated alumina particles (30 μm); G: glazed with a thin film of low-fusing porcelain glaze; GH: glazed and etched with 10% hydrofluoridric acid for 60 s. Mechanical cycling (1.2 × 106 cycles, 200 N, 3.8 Hz) and flexural strength test (1 mm/min — 1000 kg cell) were performed. Two-way ANOVA and Tukey's were used for statistical test (α = 0.05). Weibull analysis was used to evaluate the strength reliability. Samples were analyzed via (1) an optical profilometer to determine the surface roughness (Ra); (2) an X-ray diffraction (XRD) to evaluate phase transformations; and (3) a SEM equipped with an energy dispersive X-ray spectroscopy (EDX) to elucidate morphological properties and chemical compositions. Results: Regardless of the surface treatment (p = 0.5459) (Cn: 560.16 MPa; Gn: 573.36 MPa; An: 643.51 MPa; GHn: 542.94 MPa; Cp: 628.04 MPa; Gp: 641.90 MPa; Ap: 554.47 MPa; GHp :602.84 MPa) and extrinsic pigmentation (p = 0.1280) there was no difference in the flexural strength among the experimental groups. According to the XRD analysis, phase transformations occurred in the An group (t → m) and in Ap group (t → c). Surface roughness was affected by surface treatments (An — p = 0.001) and extrinsic pigmentation (Gp — p = 0.001). Significance: The biaxial flexural strength of the tested samples was not affected neither by surface treatments nor by pigmentation, although it can cause phase transformation and promote surface roughness. Department of Restorative Dentistry Federal University of Juiz de Fora (UFJF) Juiz de Fora/MG Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University – UNESP Federal University of Rio Grande do Norte/UFRN Health Science Center Department of Dentistry New York University College of Dentistry Department of Biomaterials and Biomimetics, 433 First Avenue, Room 810 Department of Dental Materials and Prosthodontics Institute of Science and Technology São Paulo State University – UNESP National Institute of Dental and Craniofacial Research: R01DE026279 National Institute of Dental and Craniofacial Research: R01DE026772

To evaluate the effect of cleaning methods on the deposition of silica on yttria-stabilized zirconium dioxide (Y-TZP) surface and on the silane-silica mediated bond strength between Y-TZP and resin cement.Y-TZP slabs were air-abraded with 30μm silica-coated alumina particles and distributed in three groups: no cleaning, cleaning with a stream of oil-free air/water spray for 5s and cleaning with an ultrasonic bath in water for 10min. The distribution of Si on the Y-TZP surfaces was recorded using energy dispersive spectroscopy (EDS). After the treatment was applied, Y-TZP slabs (n=20) received a primer application and resin cement cylinders were built on the surface. After storage (24h) in water storage or 3 months plus thermocycling; n=10), microshear bond strength test (μSBS) was performed. X- ray Photoelectron Spectroscopy (XPS) characterized the chemical bonds between the silica layer and the silane-containing primer. Data were analyzed using ANOVA and Tukey test, as well as Weibull analysis (α=0.05).Cleaning method had a significant effect on the amount of Si deposited on zirconia surface (p0.001) and, consequently, on bond strength (p0.001). Storage/aging also had a significant effect on bond strength (p0.001). Low values of Weibull moduli for bond strength were observed for all groups after aging. XPS showed silane-silica chemical interaction for all groups.The silica deposited by tribochemical coating to Y-TZP was removed by the cleaning methods evaluated, compromising bond strength. Stability of the bonding is also a concern when no cleaning method is applied.

Objectives Understand how cooling protocols control the microstructure and mechanical properties of veneering porcelains. Methods Two porcelain powders were selected, one used to veneer metallic frameworks (VM13) and one for zirconia frameworks (VM9). After the last firing cycle, the monolithic specimens were subjected to two cooling protocols: slow and fast. Flexural strength (FS) was evaluated by three-point beam bending and fracture toughness (KIC) was evaluated by the single-edge V-notch beam (SEVNB) method. Scanning electron microscopy (SEM) was performed to determine the leucite crystal volume fraction (%), particle size, and matrix microcrack density. The results were compared by analysis of variances (ANOVA) and Tukey’s multiple comparison test. Results The mechanical properties were significantly (p Significance Controlled crystallization using slow cooling can be applied as a means of strengthening dental porcelains. However, the benefits of slow cooling may be partially offset by increasing the microcrack density in the glass matrix. To achieve the maximum benefit of slow cooling, it is recommending to develop heat treatments to produce porcelain with fine-grained and homogenously dispersed leucite crystals to achieve minimal glass matrix microcracking.

Objectives The aim of the study was to evaluate the influence of contamination and different cleaning methods on the tensile bond strength with a phosphate monomer containing luting resin to zirconia ceramic. Methods After the contamination with saliva or silicone disclosing agent, 228 polished and airborne-particle abraded zirconia discs were ultrasonically cleaned with 99% isopropanol. In a second step, the specimens were either treated with argon-oxygen plasma, air plasma, enzymatic cleaning agent or did not undergo an additional cleaning process. Uncontaminated zirconia specimens were used as the control group. X-ray photoelectron spectroscopy (XPS) was used for chemical analysis of the bonding surfaces of specimens. Plexiglas tubes filled with composite resin were bonded to zirconia specimens with a phosphate monomer containing luting resin. Tensile bond strength (TBS) was tested after 3 days or 150 days water storage with 37,500 thermal cycles. Results XPS revealed a decrease of the carbon/oxygen ratio after plasma treatment and an increase after treatment with an enzymatic cleaning agent in all groups. All contaminated specimens showed high and durable TBS after cleaning with a combination of isopropanol and a non-thermal atmospheric plasma. After the cleaning with enzymatic cleaning agent the TBS was significantly reduced in all groups after 150 days thermal cycling. Significance The combination of isopropanol and plasma cleaning was effective in removing salvia and disclosing agent contamination. Enzymatic clearing agent was not able to remove contamination effectively and had a negative impact on the TBS of non-contaminated specimens.

Objective To test the impact of zirconia pretreatment and aging on flexural strength and phase structure. Methods For flexural strength measurements, 180 3Y-TZP0.25 specimens were fabricated and pretreated: (i) air-abraded (105-μm alumina, 0.25 MPa), (ii) air-abraded (50-μm alumina, 0.25 MPa), (iii) air-abraded (30-μm silica-coated alumina, 0.28 MPa) (iv) non-pretreated. Each pretreated group (n = 15) was aged: (a) hydrothermal (134 °C, 0.23 MPa, 2 h) (b) in a mastication simulator (1,200,000×, 5/55 °C) and (c) not aged. The fractured specimens were stored dry for 5 years (23 °C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP0.25 (n = 12) and 3Y-TZP0.05 (n = 8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4 MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffe post hoc test and partial-eta-squared (ƞp²) (α = 0.05). Results The highest impact on flexural strength was exerted by the pretreatment (ηP² = 0.261, p Significance Air-abrasion with 30-μm silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP0.25 and 3Y-TZP0.05. For air-abrasion using alumina powder lower pressure should be used.

Objective To assess whether a thermal annealing with a monoclinic zirconia (mZrO2) nanoparticle coating can improve the reliability of sandblasted yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and maintain its mechanical strength. Methods Commercially available Y-TZP (Lava Frame, 3M Dental Products) disks were sintered and surface-treated as follows: AS (as sintered, with no treatment); SB (sandblasting); SB-TA (sandblasting followed by thermal annealing at 1000 °C); and SB-mZr-TA (sandblasting followed by thermal annealing at 1000 °C with the mZrO2 nanoparticle coating). The mZrO2 nanoparticles of 21 nm in size were prepared by a hydrothermal method, and coated onto Y-TZP sintered disks as a 5 g/L ethanol dispersion. Biaxial flexural strength (S) was measured using the piston-on-three-ball test, and reliability was evaluated by the Weibull modulus (m). Results Biaxial flexural tests showed a significant increase in the strength of Group SB (SSB = 1445 ± 191 MPa) compared with Group AS (SAS = 1071 ± 112 MPa). The thermal annealing improved the reliabilities of the sandblasted Y-TZP (mSB-TA = 20.14 and mSB-mZr-TA = 21.33), as compared with Group SB (mSB = 7.77). However, the conventional thermal annealing without the mZrO2 coating caused a significant decrease in the strength of sandblasted Y-TZP (SSB-TA = 1273 ± 65 MPa). Importantly, the mZrO2 coating prevented the decrease in the strength caused by conventional thermal annealing (SSB-mZr-TA = 1379 ± 65 MPa). Significance The thermal annealing with the mZrO2 nanoparticle coating can improve the reliability of sandblasted Y-TZP and maintain its mechanical strength, which would otherwise be decreased by the conventional annealing process.

The aim of this study is to evaluate the effect of fusion sputtering surface treatment on the microshear bond strength of zirconia and self-adhesive MDP-containing resin cement.Thirty-six zirconia discs received one of the following treatments: fusion sputtering, airborne particle abrasion with 50-μm aluminum oxide particles, while as-sintered specimens served as a control. Four treated zirconia samples from each group were examined using 3D laser scanning microscope to assess the surface roughness and scanning electron microscope to study the surface topography. The specimens of each group were bonded to composite micro discs using MDP-containing self-adhesive resin cement (Panavia SA cement plus). The specimens were thermocycled for 5000 cycles between 5 and 55 °C. Microshear bond strength test was performed using universal testing machine until bonding failure. Failure modes and fracture surfaces was evaluated using scanning electron microscope.The fusion sputtering surface treatment significantly influenced zirconia-resin bond strength (p 0.001). The highest mean microshear bond strength value was observed in fusion sputtering treatment (23.18 ± 4.38). The lowest value was observed in as-sintered zirconia surfaces (7.23 ± 6.26).Fusion sputtering surface treatment enhanced the microshear bond strength of zirconia and resin cement.

Objectives A systematic review of in vitro studies was conducted to assess the effect of thermal treatments on flexural strength or critical load to failure of porcelain-veneered zirconia (PVZ). Sources Literature searches were performed up to June 2018 in PubMed/MEDLINE, Scopus and Web of Science databases, with no publication year or language limits. Data From 393 relevant studies, 21 were selected for full-text analysis, from which 7 failed to meet the inclusion criteria. The 14 remaining papers were included in the systematic review: 8 for meta-analysis and 6 restricted to descriptive analyses. Hand searching of reference lists resulted in no additional papers. Study selection In vitro studies using PVZ specimens testing the influence of thermal treatments on the fracture resistance to monotonic or cyclic loading. Papers evaluating cooling rate were divided into those applying fast cooling from above the porcelain glass transition temperature ( T g ), or from below it. Meta-analyses were performed separately for flexural strength and critical load to failure, using random effects at a 5% significance level. Conclusions Delaying furnace opening at a temperature below the porcelain T g is advised for PVZ restorations, in order to improve their fracture resistance. Additional information is required to confirm the apparent beneficial effect of self-glaze and repeated veneer firings on the mechanical properties of these restorations. Finally, in order to obtain conclusive and relevant evidence regarding thermal treatments and the fracture resistance of PVZs, future studies should concentrate on anatomically-correct crown specimens.

Objective The objectives of the present study were: (1) to analyze the dispersion and optical properties of suspensions with various volume fractions of zirconia, and (2) to assess the influence of zirconia volume fraction on the microstructure and physical properties of products produced by the additive manufacturing and sintering process. Methods Zirconia specimens were fabricated by an additive manufacturing technique using a DLP (digital light processing) system. The zirconia suspensions were divided into six groups based on zirconia volume fraction within the range of 48–58 vol%. Results The maximum volume fraction of zirconia in suspensions possible for printing was 58 vol%. The cure depth of the zirconia suspensions decreased as the volume fraction increased. The cure depth was greater than 100 μm after 15 s photocuring in all groups. Geometrical overgrowth tended to increase gradually as the volume fraction of zirconia increased within the range of 28.55–36.94%. The 3-point bending strength of the specimens increased as the volume fraction of zirconia in the suspension increased, reaching a maximum value of 674.74 ± 32.35 MPa for a volume fraction of 58 vol%. Cracks were observed on the surfaces of zirconia specimens and these cracks increased in number as zirconia volume fraction decreased. Significance In this experiment, the viscosity of zirconia suspensions sharply increased from a volume fraction of 54 vol%. Because of the very high viscosity, 58 vol% was the maximum volume fraction possible for additive manufacturing. After polymerization, all specimens showed some distortion due to geometrical overgrowth. The maximum 3-point bending strength was 674.74 ± 32.35 MPa for a volume fraction of 58 vol%. But the maximum strength of sintered zirconia prepared by additive manufacturing is inferior to that of conventionally sintered zirconia.

OBJECTIVES: To fully realize the range of indication and clinical advantages of the new multi-layered zirconias, a comprehensive understanding of their chemical composition, microstructure, low temperature degradation (LTD) resistance, and translucency properties is paramount. METHODS: A zirconia system (Katana, Kuraray Noritake), including 3 distinct grades of multi-layered zirconias, was selected for study: Ultra Translucent Multi-layered zirconia (UTML), Super Translucent Multi-layered zirconia (STML), and Multi-layered zirconia (ML). For different materials and their individual layers, the chemical composition, zirconia phase fractions, and microstructure were determined by x-ray fluorescence (XRF), x-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). Also, their resistance to LTD and translucency properties were characterized. RESULTS: Our findings revealed no major differences amongst layers, but the 3 materials were very distinct—UTML: 5Y-PSZ (5 mol% yttria-partially-stabilized zirconia) with ~75 wt% cubic content and a 4.05 (±0.85) μm average grain size, STML: 4Y-PSZ with ~65 wt% cubic content and a 2.81 (±0.17) μm average grain size, and ML: 3Y-PSZ with

Objective To determine the thermal expansion of a porcelain (VM9) and tetragonal zirconia (Y-TZP) as well as the deflection upon re-heating and cooling of a bilayer fabricated from these two materials after slow and rapid cooling during initial fabrication. Methods The coefficient of thermal expansion (CTE) of bulk porcelain and Y-TZP as well as bilayer beam deflection was measured with a novel non-contact optical dilatometer. The influence of cooling rate during initial fabrication of the porcelain–zirconia bilayer and the bulk porcelain during subsequent heating and cooling is investigated. Specimens were heated to 900 °C in the dilatometer, well in excess of the glass transition temperature (Tg) and softening temperature (Ts) of the porcelain. Results The thermal expansion of the porcelain above Tg exhibits a threefold increase in CTE over that observed below Tg. Observations of the bilayer deflection reflect the difference in the CTE of the component materials and enable Tg and Ts temperatures for the porcelain to be estimated. Initial cooling rate of the porcelain and porcelain-YTZP bilayer was found to have a profound influence on the subsequent response to slow reheating and cooling as well as the resultant residual deflection. Significance The estimation of the residual stress and potential for chipping of porcelain–zirconia dental restorative systems should not be based solely on thermal expansion data measured below Tg.

Objective In the past, discrepancies between laboratory results and clinical behavior have been observed for all-ceramic restorations. This analysis of fracture resistance of zirconia-based inlay-retained fixed partial dentures (IRFPDs) aimed at identifying correlations between an in-vitro test setup and the clinical situation. The effects of tooth material, tooth mobility, restoration design, load direction, and different cements were taken into account. Methods The in-vitro test model and IRFPD were reverse engineered (Geomagic DesignX) and meshed predominantly with hexahedral elements (approx. 230,000 elements). Homogenous, linear-elastic behavior was assumed for all materials. On the basis of the calculated stresses (ANSYS 18.2) and already known strength distributions for the restorative materials fracture resistance of the complete restoration and force at initial damage (fracture within the veneer) was estimated on the basis of the principal stress hypothesis. Differences depending on the assumed clinical situation and effects of different variables on fracture resistance were evaluated. Results All variables tested in the finite element analysis affected the calculated fracture resistance of the IRFPD. Use of resin teeth led to an underestimation of fracture resistance by up to −57%, whereas fracture resistance of IRFPDs on metal abutment teeth was close to the clinical reference (−6% to +15%). Good correlation between the clinical scenario and that using metal teeth could only be achieved when the natural resilience of the abutment teeth was simulated. Significance When testing fracture resistance of zirconia-based IRFPDs, metal abutment teeth in combination with simulated tooth resilience can reflect the clinical situation accurately.

Objective Chipping fractures of the veneering porcelain are frequently reported for veneered all-ceramic crowns. In the present study, the edge chipping test is used to measure the toughness and the edge chipping resistance of veneered zirconia and porcelain-fused-to-metal (PFM). The aim is to describe an edge chipping method developed with the use of a universal testing machine and to verify the accuracy of this method to determine the influence of residual thermal stresses on the chipping fracture resistance of veneering porcelain. A finite element analysis (FEA) was used to study the residual stress profiles within the veneering porcelain. Methods Veneered zirconia and PFM bar specimens were subjected to either a fast or a slow cooling protocol. The chipping resistances were measured using the edge chipping method. The load was applied in two different directions, in which the Vickers indenter was placed in the veneering porcelain either parallel or perpendicular to the veneer/framework interface. The mean edge chipping resistance (ReA) and fracture toughness (KC) values were analysed. ReA was calculated by dividing the critical force to cause the chip by the edge distance. KC was given by a fracture analysis that correlates the critical chipping load (FC) regarding edge distance (d) and material toughness via KC = FC/(βd1.5). Results The ReA revealed similar values (p > 0.005) of chipping resistance for loads applied in the parallel direction regardless of framework material and cooling protocol. For loads applied in the perpendicular direction to the veneer/framework interface, the most chip resistant materials were slow cooled veneered zirconia (251.0 N/mm) and the PFM fast cooled (190.1 N/mm). KC values are similar to that for monolithic porcelain (0.9 MPa.√m), with slightly higher values (1.2 MPa.√m) for thermally stressed PFM fast cooled and veneered zirconia slow cooled groups. Significance The developed and reported edge chipping method allows for the precise alignment of the indenter in any predetermined distance from the edge. The edge chipping method could be useful in determining the different states of residual thermal stresses on the veneering porcelain.

Objective To investigate the long-term stability of a metal-free zirconia two-piece implant assembled with a carbon fiber-reinforced (CRF) screw by means of transformation propagation, potential changes in surface roughness, the gap size of the implant-abutment connection, and fracture load values. Methods In a combined procedure, two-piece implants made from alumina-toughened zirconia were dynamically loaded (107 cycles) and hydrothermally aged (85°, 60 days). Implants made from titanium (Ti) and a titanium–zirconium (TiZr) alloy with a titanium abutment screw served as control. Transformation propagation (ATZ) and gap size of the IAC were monitored at cross-sections by scanning electron microscopy (SEM). Furthermore, changes in surface roughness of ATZ implants were measured. Finally, implants were statically loaded to fracture. Linear regression models and pairwise comparisons were used for statistical analyses. Results Independent of the implant bulk material, dynamic loading/hydrothermal aging did not decrease fracture resistance (p = 0.704). All test and control implants fractured at mean loads >1100 N. Gap size of the IAC remained stable ( Significance Combined hydrothermal aging and dynamic loading did not affect the above-mentioned parameters of the evaluated two-piece ATZ implant. Mean fracture loads >1100 N suggest a reliable clinical application.

Made available in DSpace on 2018-12-11T16:54:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-01 Objectives: The aim of this study was to characterize the microstructure of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics and evaluate their mechanical properties before and after the crystallization firing process (CFP). Methods: Field emission-scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed for microstructural characterization. To evaluate the pattern of crystallization and the molecular composition of ZLS glass-ceramics, was used X-ray diffraction (XRD). Vickers hardness, fracture toughness by the indentation method, and biaxial flexural strength were also measured. One hundred and forty ceramic discs were produced (diameter = 12 mm; thickness = 1.2 mm) and allocated among four groups (n = 30): Sfir, Sunf-ZLS Vita Suprinity; and Cfir and Cunf-ZLS Celtra Duo; fired and unfired, respectively. Statistical analysis was performed and Weibull failure probabilities were calculated. Results: Cfir showed the highest characteristic strength (251.25 MPa) and hardness (693.333 ± 10.85 GPa). Conversely, Sunf presented the lowest characteristic strength (106.95 MPa) and significantly lowest hardness (597.533 ± 33.97 GPa). According to Weibull analysis, Sunf had the highest structural reliability (m = 7.07), while Sfir presented the lowest (m = 5.38). The CFP was necessary to crystallize zirconia in the partially crystallized ZLS glass-ceramics. Sfir had a lower percentage of crystallized zirconia than did Cfir. Fractographic analyses showed that all failures initiated from an inherent critical defect in Sunf and from processing defects in the remaining groups. Significance: The CFP had a direct influence on the flexural strength and microstructural characteristics of both ZLS materials. Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue Faculty of Dental Medicine Lisbon University Aeronautics Technological Institute (ITA), 50 Praça Marechal Eduardo Gomes Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue

Objective Herein we investigated the flexural strengths of bilayered ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) disks using different veneering porcelains. Methods Commercial (VITA VM9, Cercon Ceram Kiss, and IPS e.max Ceram) and experimental porcelains (Vintage ZR with coefficient of thermal expansions: CTEs of 8.45, 9.04, and 9.61 ppm/°C) with various layer thicknesses (1.0, 1.5, and 2.0 mm) were applied to Ce-TZP/A disks (0.8 mm thickness, n = 180). Biaxial flexural tests of the specimens with the porcelain layer in tension were evaluated based on the piston-on-three-ball method (ISO 6872: 2008). The calculated strengths were statistically analyzed using the two-parameter Weibull distribution with the maximum likelihood estimation. Results Although no significant differences were observed among the experimental porcelains, most specimens with the thinner layer of commercial porcelain showed higher Weibull characteristic strengths at the external surfaces than those with the thicker layer. Irrespective of the porcelain material, the thinner porcelain layer showed significantly higher strengths at the interface between the layers. Fracture origins were always observed at the bottom surface and continuously propagated into Ce-TZP/A substrates. The maximum tensile stress was located at the interface in specimens with the 1.0 mm porcelain layer, except for IPS e.max Ceram. Porcelain delamination was dominant in the case of the higher CTE value and thicker layer thickness of the porcelain. Significance The calculated biaxial flexural strengths and the stress distributions for bilayered Ce-TZP/A disks were dependent on the porcelain materials. Optimum behavior was observed for a combination of a small CTE mismatch between the materials and a low core-to-porcelain thickness ratio.

Objective The objective of the present study is to understand the role of yttria stabilized zirconia (YSZ) in achieving the desired spectrum of clinically relevant mechanical properties (hardness, elastic modulus, fracture toughness and brittleness index) and chemical solubility of mica glass ceramics. Methods The glass–zirconia mixtures with varying amounts of YSZ (0, 5, 10, 15 and 20 wt.%) were ball milled, compacted and sintered to obtain pellets of glass ceramic-YSZ composites. Phase analysis was carried out using X-ray diffraction and microstructural characterization with SEM revealed the crystal morphology of the composites. Mechanical properties such as Vickers hardness, elastic modulus, indentation fracture toughness and chemical solubility were assessed. Results Phase analysis of sintered pellets of glass ceramic-YSZ composites revealed the characteristic peaks of fluorophlogopite (FPP) and tetragonal zirconia. Microstructural investigation showed plate and lath-like interlocking mica crystals with embedded zirconia. Vickers hardness of 9.2 GPa, elastic modulus of 125 GPa, indentation toughness of 3.6 MPa·m1/2, and chemical solubility of 30 μg/cm2 (well below the permissible limit) were recorded with mica glass ceramics containing 20 wt.% YSZ. Significance An increase in hardness and toughness of the glass ceramic-YSZ composites with no compromise on their brittleness index and chemical solubility has been observed. Such spectrum of properties can be utilised for developing a machinable ceramic for low stress bearing inlays, onlays and veneers.

The study aims at comparing the fracture resistance of different restorative materials used in dental endocrown restorations and respective endocrown restorations under a quasi-static compressive load using acoustic emission (AE) method.Five restorative materials were used in this study. The restorative materials were manufactured into discs 13mm in diameter and 5mm thick, which were then divided into 5 groups and included into Type 1: Group B: zirconium dioxide (Prettau zirconia); Group C: ceramics (IPS e.max Press); Group D: metal ceramics (GC Initial MC+Nicrallium N2 BCS); Group E: composite resin (Nano Q); Group F: luting cement (RelyX™ U200). Twenty-five extracted human molars were divided into 5 groups and included into Type 2: Group A: control, no restoration; Group BE: restored by zirconium dioxide endocrowns; Group CE: restored by ceramic endocrowns; Group DE: restored by metal ceramic endocrowns; Group EE: restored by composite resin endocrowns. An increasing load was applied to the center of the samples with a hard steel ball until a fracture occurred. The loading rate was 0.12mm/min. An AE system was used to monitor the fracture of the samples. The load corresponding to the first AE event and the final fracture load were used to evaluate the fracture resistance of the restored teeth. The data were analyzed using ANOVA and Tukey's post hot test (α=0.05).A lower threshold of 220μV was selected to exclude spurious background signals. For the initial fracture load of Type 1 samples, Group F (0.029kN)Group E (0.039kN)Group D (0.056kN)Group C (0.253kN)Group B (intact). The same trend was found for the final fracture load, i.e., Group F (1.289kN)Group E (1.735kN)Group D (3.362kN)Group C (6.449kN)Group B (intact). For the initial and final fracture load, statistically significant differences (p0.05) were found between group C and the others groups. For the initial fracture load of Type 2 samples, Group EE (0.069kN)Group DE (0.072kN)Group CE (0.148kN)Group BE (2.511kN). For the final fracture load, Group EE (1.533kN)Group CE (2.726kN)Group BE (3.082 kN)Group DE (3.320kN). The initial fracture load of the ceramic samples is somewhat higher than that for the endocrown restorations with the endocrowns made of this material (0.253 and 0.148kN, respectively). At the same time, for the metal ceramic and composite resin samples, the initial fracture loads are somewhat lower than in case of compression of the endocrown restorations with the endocrowns made of these materials (0.056 and 0.072kN; 0.039 and 0.069kN, respectively). The final fracture load of all the samples of the dental materials exceeds the strength of the respective endocrown restorations. The final fracture loads of the endocrown restorations with zirconium dioxide and ceramic endocrowns (3.082 and 2.726kN, respectively) are significantly lower than the final fracture load of the respective endocrown materials (intact and 6.449kN, respectively).Dental restorations should be made of high-strength materials. Zirconia displayed the highest fracture strength, while composite resin had the lowest fracture strength out of the materials used for the endocrowns. For teeth restored with endocrowns, the use of metal ceramics as endocrown material may lower the risk of failure during clinical use.

Objective To assess the change in surface roughness of nanohybrid resin composite (Tetric EvoCeram) after antagonist wear against monolithic zirconia and lithium disilicate ceramics through a simulated chewing test using a three-dimensional (3D) profilometer. Methods A total of 40 Tetric EvoCeram™ resin composite specimens against either a Lava™ Plus zirconia antagonist (n = 20) or IPS e.max Press lithium disilicate antagonist (n = 20) were prepared for the study. The surface roughness profiles of each resin composite before and after an in-vitro simulated chewing test were analysed using a 3D profilometer and Talymap software. After the simulated chewing, the surface profiles of representative Tetric EvoCeram specimens from each group were analysed using scanning electron microscopy. Independent t-test and paired t-test were used for statistical analysis. Results For both lithium disilicate and zirconia groups, all surface roughness parameters (Ra, Rt, Sa, Sq,) of Tetric EvoCeram were significantly higher post-chewing compared to pre-chewing (p < 0.05); the post-chewing surface roughness parameters of Tetric EvoCeram for the lithium disilicate group were significantly higher (p < 0.05) than in the zirconia group. Significance This chewing simulation test showed that Tetric EvoCeram composites exhibited a rougher surface when opposing lithium disilicate ceramic compared to opposing zirconia ceramic.

Objective The current laboratory study was to investigate the effect of different sterilization treatments on surface characteristics of zirconia, and biofilm formation on zirconia surface after exposure to these sterilization treatments. Methods Commercially available zirconia discs (Cerconbase, Degu-Dent, Hanau, Germany) were prepared and polished to the same value of surface roughness. The discs were treated with one of the following sterilization methods steam autoclave sterilization, dry heat sterilization, ultraviolet C (UVC) irradiation, and gamma (γ) ray irradiation. The characteristics of zirconia surfaces were evaluated by scanning electron microscopy (SEM), surface roughness, surface free energy (SFE), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) measurements. Then, Staphylococcus aureus (S.a.) and Porphyromonas gingivalis (P.g.) bacteria were used and cultured on the respective sterilized zirconia surfaces. The amount of biofilm formation on zirconia surface was quantified by colony forming unit (CFU) counts. Results Significant modifications were detected on the colour and SFE of zirconia. The colour of zirconia samples after UVC irradiation became light yellow whilst dark brown colour was observed after gamma ray irradiation. Moreover, UVC and gamma ray irradiation increased the hydrophilicity of zirconia surface. Overall, dry heat sterilized samples showed the significantly lowest amount of bacteria growth on zirconia, while UVC and gamma ray irradiation resulted in the highest. Significance It is evident that various sterilization methods could change the surface which contribute to different biofilm formation and colour on zirconia.

Objective Separately addressing the fatigue resistance (ISO 14801, evaluation of final product) and aging behavior (ISO 13356, standardized sample) of oral implants made from yttria-stabilized zirconia proved to be insufficient in verifying their long-term stability, since (1) implant processing is known to significantly influence transformation kinetics and (2) aging, up from a certain level, is liable to decrease fatigue resistance. Therefore, the aim of this investigation was to apply a new testing protocol considering environmental conditions adequately inducing aging during dynamic fatigue. Methods Zirconia implants were dynamically loaded (107 cycles), hydrothermally aged (85°, 60 days) or subjected to both treatments simultaneously. Subsequent, monoclinic intensity ratios (Xm) were obtained by locally resolved X-ray microdiffraction (μ-XRD2). Transformation propagation was monitored at cross-sections by μ-Raman spectroscopy and scanning electron microscopy (SEM). Finally, implants were statically loaded to fracture. Linear regression models (fracture load) and mixed models (Xm) were used for statistical analyses. Results All treatments resulted in increased fracture load (p ≤ 0.005), indicating the formation of transformation induced compressive stresses around surface defects during all treatment modalities. However, only hydrothermal and combinational treatment were found to increase Xm (p < 0.001). No change in Xm was observed for solely dynamically loaded samples (p ≥ 0.524). Depending on the variable observed, a monoclinic layer thickness of 1–2 μm (SEM) or 6–8 μm (Raman spectroscopy) was measured at surfaces exposed to water during treatments. Significance Hydrothermal aging was successfully induced during dynamic fatigue. Therefore, the presented setup might serve as reference protocol for ensuring pre-clinically long-term reliability of zirconia oral implants.

Objective The aim of this work is to generate micrometric linear patterns with different topography on dental grade zirconia by means of UV laser interference and to assess the quality of the produced surface, both in term of the geometry produced and of the surface damage induced in the material. Methods The third harmonic of a Q-switched Nd:YAG laser (355 nm, pulse duration of 10 ns and repetition rate of 1 Hz) was employed to pattern the surface of 3Y-TZP with micrometric-spaced lines. The resulting topography was characterized with White Light Interferometry and Scanning electron microscopy: pattern depth ( H ), amplitude roughness parameters ( S a , filtered- S a ), Fourier spatial analysis and collateral damages were related to laser fluence and number of pulses employed. Results With our experimental setup, line-patterning of zirconia surfaces can be achieved with periodicities comprised within 5 and 15 μm. Tuning laser parameters allows varying independently pattern depth, overall roughness and surface finish. Increasing both fluence and number of pulses allows producing deeper patterns (maximum achievable depth of 1 μm). However, increasing the number of pulses has a detrimental effect on the quality of the produced lines. Surface damage (intergranular cracking, open porosity and nano-droplets formation) can be generated, depending on laser parameters. Significance This work provides a parametric analysis of surface patterning by laser interference on 3Y-TZP. Best conditions in terms of quality of the produced pattern and minimum material damage are obtained for low number of pulses with high laser fluence. With the employed method we can produce zirconia materials with controlled topography that are expected to enhance biological response and mechanical performance of dental components.

Objective To evaluate the microstructure and mechanical behavior of polymer-infiltrated zirconia ceramics as a function of Fe 2 O 3 concentration (0–0.3 mol%). Methods Polymer-infiltrated zirconia ceramics with different concentrations of Fe 2 O 3 were prepared by infiltration and polymerization. XRD was employed to determine phase structure. The microstructure and fracture mechanism was observed by SEM. Flexural strength and fracture toughness were measured by three-point bending method and single-edge-notched beam method, respectively. Data were analyzed by Weibull distribution. A nanoindentation system was employed to determine elastic modulus and hardness. Results With increasing content of Fe 2 O 3 , the flexural strength, fracture toughness, elastic modulus and hardness are all greatly enhanced and the chromatic behavior also improves significantly. As a tradeoff made between strength and elastic modulus, specimen containing 0.2 mol% Fe 2 O 3 is found to be the better one, with flexural strength and fracture toughness values being 336.8 MPa and 3.91 MPa m 1/2 , respectively. Moreover, it maintains a relatively low elastic modulus of 88.2 GPa and a moderate hardness of 4.8 GPa, close to those of natural enamel. Significance This polymer-infiltrated zirconia ceramic material is a dental material of biomimetic chromatic and mechanical properties.

To evaluate the effect of two aging methods (mechanical cycling and autoclave) on the mechanical behavior of veneer and framework ceramic specimens with different configurations (monolithic, two and three-layers).Three ceramics used as framework for fixed dental prostheses (YZ-Vita In-Ceram YZ; IZ-Vita In-Ceram Zirconia; AL-Vita In-Ceram AL) and two veneering porcelains (VM7 and VM9) were studied. Bar-shaped specimens were produced in three different designs: monolithic, two layers (porcelain-framework) and three layers (porcelain-framework-porcelain). Specimens were tested for three-point flexural strength at 1MPa/s in 37°C artificial saliva. Three different experimental conditions were evaluated (n=10): control; mechanical cycling (2Hz, 37°C artificial saliva); and autoclave aging (134°C, 2 bars, 5h). Bi-layered specimens were tested in both conditions: with porcelain or framework ceramic under tension. Fracture surfaces were analyzed using stereomicroscope and scanning electron microscopy. Results were statistically analyzed using Kruskal-Wallis and Student-Newman-Keuls tests.Only for AL group, mechanical cycling and autoclave aging significantly decreased the flexural strength values in comparison to the control (p0.01). YZ, AL, VM7 and VM9 monolithic groups showed no strength degradation. For multi-layered specimens, when the porcelain layer was tested in tension (bi and tri-layers), the aging methods evaluated also had no effect on strength (p≥0.05). Total and partial failure modes were identified.Mechanical cycling and autoclave aging protocols had no effect on the flexural strength values and failure behavior of YZ and IZ ceramic structures. Yet, AL monolithic structures showed a significant decrease in flexural strength with any of the aging methods.

The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes.Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05.As grit size of the diamond disc increased, zirconia surface roughness decreased (p0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups.Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength.

Objectives: Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional toughness. Within these components the residual stress and crystallographic phase of YPSZ close to the interface are highly influential in the primary failure mode; near interface porcelain chipping. In order to improve present understanding of this behaviour, characterisation of these parameters is needed at an improved spatial resolution.Methods: In this study transmission micro-focus X-ray Diffraction, Raman spectroscopy, and focused ion beam milling residual stress analysis techniques have, for the first time, been used to quantify and cross-validate the microscale spatial variation of phase and residual stress of YPSZ in a prosthesis cross-section.Results: The results of all techniques were found to be comparable and complementary. Monoclinic YPSZ was observed within the first 10m of the YPSZ-porcelain interface with a maximum volume fraction of 60%. Tensile stresses were observed within the first 150m of the interface with a maximum value of ≈ 300 MPa at 50m from the interface. The remainder of the coping was in mild compression at ≈ − 30 MPa, with shear stresses of a similar magnitude also being induced by the YPSZ phase transformation.Significance: The analysis indicates thatthe interaction between phase transformation, residual stress and porcelain creep at YPSZ-porcelain interface results in a localised porcelain fracture toughness reduction. This explains the increased propensity of failure at this location, and can be used as a basis for improving prosthesis design.

Objective. The aim of this study was to evaluate whether the mechanical properties of the modern dental composites can be improved by using tetrapodal ZnO particles as fillers in a Bis-GMA/TEGDMA matrix. Another aim was to test whether the mechanical properties of the composite are influenced by functionalization of the ZnO particles with lauric acid to achieve antibacterial activity. Methods. Different filler materials and particle shapes (spherical zirconia, spherical zinc oxide, tetrapodal zinc oxide) were used to produce Bis-GMA/TEGDMA based composites with a filler content of 40 wt.-% and 60 wt.-%, respectively. In addition, functionalization with lauric acid was investigated. For the biaxial flexural strength testing 104 test disks (N = 8) with a diameter of 15 mm and a thickness of 1.5 mm were produced. Results. Functionalization with lauric acid resulted in a decrease in biaxial flexural strength for all filler materials. The biaxial flexural strength decreased when using a higher filler content with spherical particles but increased when using tetrapodal zinc oxide particles. Significance. A higher durability of the composites using tetrapodal zinc oxide particles. An antibacterial functionalization with lauric acid cannot be recommended as the mechanical stability of the composite will be reduced. (C )2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The aim of this study was to assess the mechanical properties of recently introduced zirconia reinforced lithium silicate glass-ceramic.Two types of CAD/CAM glass-ceramics (Vita Suprinity (VS); zirconia reinforced lithium silicate and IPS e.max CAD (IC); lithium disilicate) were used. Fracture toughness, flexural strength, elastic modulus, hardness, brittleness index, and microstructures were evaluated. Data were analyzed using independent t tests. Weibull analysis of flexural strength data was also performed.VS had significantly higher fracture toughness (2.31±0.17MPam(0.5)), flexural strength (443.63±38.90MPa), elastic modulus (70.44±1.97GPa), and hardness (6.53±0.49GPa) than IC (P0.001). On the other hand, VS glass-ceramic revealed significantly a higher brittleness index (2.84±0.26μm(-1/2)) (lower machinability) than IC glass-ceramic (P0.05). VS demonstrated a homogeneous fine crystalline structure while, IC revealed a structure with needle-shaped fine-grained crystals embedded in a glassy matrix. The VS glass-ceramic revealed a lower probability of failure and a higher strength than IC glass-ceramic according to Weibull analysis.The VS zirconia reinforced lithium silicate glass-ceramic revealed higher mechanical properties compared with IC lithium disilicate glass-ceramic.

Objectives To investigate the influence of the implant–abutment connection on the long-term in vitro performance and fracture resistance of two-piece zirconia implant systems for anterior application. Methods Six groups of two-piece zirconia implant systems (n = 10/group) with screw-retained (5×) or bonded (1×) connections were restored with full-contour zirconia crowns. A two-piece screw-retained titanium system served as reference. For simulating anterior loading the specimens (n = 8/group) were mounted at an angle of 135° in the chewing simulator, and subjected to thermal cycling (TC: 2 × 9000 × 5°/55 °C) and mechanical loading (ML: 3.6 × 106 × 100 N). Failed restorations were examined (scanning electron microscopy). Fracture resistance and maximum bending stress of surviving restorations were determined. 2 specimens per group were loaded to fracture after 24 h water storage without TCML. Data were statistically analyzed (ANOVA; Bonferroni; Kaplan–Meier-Log-Rank; α = 0.05). Results The bonded zirconia system and the titanium reference survived TCML without any failures. Screw-retained zirconia systems showed fractures of abutments and/or implants, partly combined with screw fracture/loosening. Failure frequency (F) varied between the groups (F = 8×: 3 groups, F = 3×: 1 group, F = 1×: 1 group). The Log-Rank-test showed significant (p = 0.000) differences. Fracture forces and maximum bending stresses (mean ± standard deviation) differed significantly (ANOVA: p = 0.000) between 233.4 ± 31.4 N/317.1 ± 42.6 N/mm2 and 404.3 ± 15.1 N/549.2 ± 20.5 N/mm2. Fracture forces after TCML were similar to 24 h fracture forces. Significance Screw-retained two-piece zirconia implant systems showed higher failure rates and lower fracture resistance than a screw-retained titanium system, and may be appropriate for clinical anterior requirements with limitations. Failures involved the abutment/implant region around the screw, indicating that the connecting design is crucial for clinical success.