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SUMMARY New resin-based restorative materials have been developed, such as computer-aided design/computer-aided manufacturing (CAD/CAM) and bulk-fill composites, as an alternative to traditional layering techniques. This study evaluated the biaxial flexural strength (BFS) before and after thermocycling of five different resin composites: one hybrid resin/ceramic CAD/CAM indirect material, Lava Ultimate CAD-CAM Restorative (LU, 3M Oral Care); a conventional composite, Filtek Z350 XT (Z350, 3M Oral Care); two bulk-fill composites, Tetric N-Ceram Bulk Fill (TBF, Ivoclar Vivadent) and Filtek Bulk Fill (FBF, 3M Oral Care); and one bulk-fill flow resin composite, Filtek Bulk Fill Flow (FBFF, 3M Oral Care). Three hundred disc-shaped specimens (6.5 mm in diameter and 0.5 mm thick) were fabricated and divided into five groups (n=30 for each composite and condition). The BFS test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min immediately (i, 24 hours) and after thermocycling (a, 500 thermal cycles of 5°C to 55°C with a 30-second dwell time). The Weibull modulus (m) and characteristic stress (η) were calculated, and a contour plot was used (m vs η) to detect differences between groups (95% two-sided confidence intervals). Significantly higher characteristic stress was observed for LUi (286.6 MPa) and Z350i (248.8 MPa) compared to the bulk-fill groups (FBFi=187.9 MPa, FBFFi=175.9 MPa, TBFi=149.9 MPa), with no differences between LUi and Z350i. Thermocycling significantly decreased the characteristic stress of all groups with the highest values observed for LUa (186.7 MPa) and Z350a (188.9 MPa) and the lowest for FBFFa (90.3 MPa). Intermediate values were observed for FBFa (151.6 MPa) and TBFa (122.8 MPa). The Weibull modulus decreased only for FBFa compared to FBFi. Composition and thermocycling significantly influenced the biaxial flexural strength of resin composite materials.

Made available in DSpace on 2022-04-28T19:43:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Universidade Estadual de Maringá Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Objective: To characterize the effects of aging on the nanomechanical properties and 3D surface topographical parameters of an experimental Zirconia Toughened Alumina (ZTA) composite compared to its respective individual counterpart materials. Methods: Disk-shaped specimens comprised of three material groups were processed: 1) ZTA 70/30 (70% alumina reinforced with 30% second-generation 3Y-TZP); 2) Zpex (Second-generation 3Y-TZP), and; 3) Al2O3 (High purity Alumina) (n = 10/material, 12 × 1 mm). After synthesis, ceramic powders were pressed, the green-body samples were sintered and polished. Nanoindentation testing was performed to record elastic modulus (E) and hardness (H). Interferometry was utilized to assess 3D surface roughness parameters (Sa, Sq), while X-ray diffraction (XRD) and scanning electron microscope (SEM) assessed the crystalline content and microstructure. All tests were performed before and after simulated aging (134°C, 2.2 bar, 20 h). Statistical analyses were performed using linear mixed-model and least square difference pos-hoc tests (α = 5%). Results: XRD spectra indicated increase of monoclinic peaks for Zpex (~18%) relative to ZTA 70/30 (~2.5%) after aging. Additionally, aging did not affect the surface roughness parameters of ZTA 70/30 and Al2O3, although a significant increase in Sa was recorded for Zpex following aging (~90 nm) (p < 0.001). Al2O3 yielded the highest H and E values (H:21 GPa, E: 254 GPa), followed by ZTA 70/30 (H: 13 GPa, E: 214 GPa) and Zpex (H:11 GPa, E: 167 GPa), all significantly different (p < 0.03). Conclusion: ZTA 70/30 and Al2O3 presented high hydrothermal stability with respect to all evaluated variables, where artificial aging significantly increased the monoclinic content and surface roughness of Zpex. Department of Prosthodontics and Periodontology University of São Paulo - Bauru School of Dentistry Department of Biomaterials New York University College of Dentistry Hansjörg Wyss Department of Plastic Surgery NYU Langone Medical Center Department of Mechanical and Aerospace Engineering NYU Tandon School of Engineering Department of Biomedical Engineering NYU Tandon School of Engineering Department of Biomaterials and Oral Biology University of São Paulo School of Dentistry Institute of Research in Nuclear Energy Department of Physics São Paulo State University Analytical Laboratory of Restorative Biomaterials - LABiom-R Federal Fluminense University (UFF) School of Dentistry Niteroi Technological Institute of Aeronautics (ITA) Integrated Biomedical Engineering and Health Sciences McMaster University Department of Physics São Paulo State University FAPESP: 2012/19078-7 Universidade Estadual de Maringá: 2016/17793-1 Universidade Estadual de Maringá: 2016/18818-8 Universidade Estadual de Maringá: 2017/19362-0 Universidade Estadual de Maringá: 2018/03072-6 Universidade Estadual de Maringá: 2019/00452-5 Universidade Estadual de Maringá: 2019/08693-1 CNPq: 304589/2017-9 CNPq: 434487/2018-0

Made available in DSpace on 2020-12-10T19:55:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) EMU Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Purpose: To synthesize a zirconia-toughened alumina (ZTA) composite with 85% alumina matrix reinforced by 15% zirconia and to characterize its optical and mechanical properties before and after artificial aging, to be compared with a conventional dental zirconia (3Y-TZP). Material and methods: After syntheses, ZTA and 3Y-TZP powders were uniaxially and isostatically pressed. Green-body samples were sintered and polished to obtain 80 disc-shaped specimens per group (12 x 1 mm, ISO 6872:2015). The crystalline content and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties were determined by the calculation of contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength test (BFS). All analyses were conducted before and after artificial aging (20h, 134 degrees C, 0.22 MPa). Optical parameters and microhardness differences were evaluated through repeated-measures analysis of variance (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results: The synthesis of the experimental ZTA composite was successful, with 98% of theoretical density, as shown in the SEM images. XRD patterns revealed typical zirconia and alumina crystalline phases. ZTA optical properties parameters showed no effect of aging, with a high CR and low TP values denoting a high masking-ability. 3Y-TZP presented lower masking-ability and aging significantly affected its optical properties. ZTA Vickers hardness, fracture toughness and Weibull parameters, including characteristic stress and Weibull modulus were not influenced by aging, while 3Y-TZP presented a significant decrease in characteristic stress and increase in fracture toughness after aging. The ZTA probability of survival for missions of 300 and 500 MPa was estimated at similar to 99% validating its use for 3-unit posterior fixed dental prostheses (FDP), and no different from conventional 3Y-TZP. At high-stress mission (800 MPa) a significant decrease in probability of survival was observed for aged 3Y-TZP (84%) and for immediate and aged ZTA (73 and 82% respectively). Conclusion: The ZTA composite presented a dense microstructure, with preservation of the crystalline content, optical and mechanical properties after artificial aging, which encourages future research to validate its potential use for large span FDP. Univ Sao Paulo, Dept Prosthodont & Periodontol, Bauru Sch Dent, Al Otavio Pinheiro Brisola 9-75, BR-17012901 Bauru, SP, Brazil Univ Sao Paulo, Sch Dent, Dept Biomat & Oral Biol, Sao Paulo, SP, Brazil Nucl & Energy Res Inst, Sao Paulo, SP, Brazil Sao Paulo State Univ, Dept Phys, Bauru, SP, Brazil NYU, Coll Dent, Dept Biomat & Biomimet, New York, NY USA NYU Langone Med Ctr, Hansjorg Wyss Dept Plast Surg, New York, NY USA NYU Tandon Sch Engn, Mech & Aerosp Engn, New York, NY USA Univ Sao Paulo, Bauru Sch Dent, Dept Biol Sci, Discipline Pharmacol, Sao Paulo, SP, Brazil Sao Paulo State Univ, Dept Phys, Bauru, SP, Brazil FAPESP: 2012/19078-7 EMU: 2016/18818-8 CNPq: 304589/2017-9 CNPq: 434487/2018-0 CAPES: 001 FAPESP: 2016/24165-7 FAPESP: 2016/18657-4 FAPESP: 2016/17793-1 FAPESP: 2017/19362-0 FAPESP: 2018/03072-6 FAPESP: 2019/00452-5 FAPESP: 2019/14798-0 FAPESP: 2019/08693-1

Made available in DSpace on 2019-10-04T12:36:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) This study's objective was to mechanically characterize and validate the synthesis method of a polycrystalline composite comprised of 80% alumina reinforced with 20% translucent zirconia (zirconia-toughened alumina, ZTA) and compare to an experimental translucent zirconia. Experimental ZTA (ZTA ZPEX 80/20) and translucent Y-TZP (ZPEX) green-state disc-shaped specimens were obtained via uniaxial/isostatic ceramic powder pressing technique. The discs were sintered using a predefined protocol after both sides of the discs were polished. The specimens were subjected to nanoindentation testing to acquire their elastic modulus (E) and hardness (H) before and after a simulated low temperature degradation (LTD) challenge. Subsequently, the fabricated discs had their 3D surface topographical (Sa/Sq) parameters assessed via interferometry before and after exposure to a simulated LTD aging protocol. The specimens were evaluated using X-ray diffraction (XRD) to assess the tetragonal-monoclinic phase transformation and via scanning electron microscopy (SEM) to evaluate the homogeneity of the surfaces and distribution of the grains. The apparent density was measured using Archimedes' principle. All of the data were statistically evaluated through repeated measures ANOVA following post-hoc comparisons using the Tukey test (p < 0.05). The XRD patterns indicated a higher increase in the monoclinic peak for ZPEX compared to ZTA ZPEX 80/20 aged. LTD aging did not have an effect on the surface roughness (Sa/Sq) for both groups (p > 0.05). A significant decrease in the E values after the aging protocol was observed for both groups (p < 0.01). While ZTA ZPEX 80/ 20 did not show statistically significant differences in the hardness values after the aging protocol (p = 0.36), ZPEX demonstrated a significant decrease in the H values (p = 0.03). For ZTA ZPEX 80/20, simulated LTD aging did not affect the tested properties, except for the E values. Although artificial aging did not affect the surface roughness of ZPEX, the E and H values significantly decreased after aging. Univ Sao Paulo, Bauru Sch Dent, Dept Prosthodont & Periodontol, Bauru, SP, Brazil NYU, Coll Dent, Dept Biomat & Biomimet, New York, NY USA NYU, Langone Med Ctr, Hansjorg Wyss Dept Plast Surg, New York, NY USA NYU, Tandon Sch Engn, Mech & Aerosp Engn, New York, NY USA Nucl & Energy Res Inst, Sao Paulo, SP, Brazil Univ Sao Paulo, Sch Dent, Dept Biomat & Oral Biol, Sao Paulo, SP, Brazil Sao Paulo State Univ, Dept Phys, Bauru, SP, Brazil Univ Estadual Campinas, Piracicaba Dent Sch, Piracicaba, Brazil Sao Paulo State Univ, Dept Phys, Bauru, SP, Brazil FAPESP: 2012/19078-7 FAPESP: EMU 2016/18818-8 FAPESP: 2016/17793-1 FAPESP: 2017/19362-0 FAPESP: 2018/03072-6 CNPq: 304589/2017-9 CNPq: 434487/2018-0 CAPES: 001