Navegando por Autor "Henriques, Bruno"

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Effect of zirconia and alumina fillers on the microstructure and mechanical strength of dental glass ionomer cements
(Bentham Open, 2016-03) Martinelli, Antonio Eduardo; Souza, Júlio C. M.; Silva, Joel B.; Aladim, Andrea; Carvalho, Oscar; Nascimento, Rubens M.; Silva, Filipe S.; Henriques, Bruno
Background: Glass-ionomer cements perform a protective effect on the dentin-pulp complex considering the F ions release and chemical bonding to the dental structures. On the other hand, those materials have poor physic-mechanical properties in comparison with the restorative resin composite. The main aim of this work was to evaluate the influence of zirconia and/or alumina fillers on the microstructure and strength of a resin modified glass-ionomer cement after thermal cycling. Methods: An in vitro experimental study was carried out on 9 groups (n = 10) of cylindrical samples (6 x 4 mm) made from resin modified glass-ionomer (Vitremer, 3M, USA) with different contents of alumina and/or zirconia fillers. A nano-hybrid resin composite was tested as a control group. Samples were mechanically characterized by axial compressive tests and electron scanning microscopy (SEM) coupled to energy dispersive X-ray spectrophotometry (EDS), before and after thermal cycling. Thermal cycling procedures were performed at 3000, 6000 and 10000 cycles in Fusayama´s artificial saliva at 5 and 60 oC. Results: An improvement of compressive strength was noticed on glass-ionomer reinforced with alumina fillers in comparison with the commercial glass ionomer. SEM images revealed the morphology and distribution of alumina or zirconia in the microstructure of glass-ionomers. Also, defects such as cracks and pores were detected on the glass-ionomer cements. The materials tested were not affected by thermal cycling in artificial saliva. Conclusion: Addition of inorganic particles at nano-scale such as alumina can increase the mechanical properties of glass-ionomer cements. However, the presence of cracks and pores present in glass-ionomer can negatively affect the mechanical properties of the material because they are areas of stress concentration
Finite element analysis of the residual thermal stresses on functionally gradated dental restorations
(Elsevier, 2015) Henriques, Bruno; Miranda, G.; Gasik, Michael; Souza, Júlio César Matias de; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel
The aim of this work was to study, using thefinite element method (FEM), the distributionof thermal residual stresses arising in metal–ceramic dental restorations after cooling fromthe processing temperature. Three different interface configurations were studied: withconventional sharp transition; one with a 50% metal–50% ceramic interlayer; and one witha compositionally functionally gradated material (FGM) interlayer. The FE analysis wasperformed based on experimental data obtained from Dynamic Mechanical Analysis (DMA)and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites.Results have shown significant benefits of using the 50% metal–50% ceramic interlayerand the FGM interlayer over the conventional sharp transition interface configuration inreduction of the thermal residual stress and improvement of stress profiles. Maximumstresses magnitudes were reduced by 10% for the crowns with 50% metal–50% ceramicinterlayer and by 20% with FGM interlayer. The reduction in stress magnitude andsmoothness of the stress distribution profile due to the gradated architectures mightexplain the improved behavior of these novel dental restorative systems relative to theconventional one, demonstrated by in-vitro studies already reported in literature.
Mechanical and chemical analyses across dental porcelain fused to CP titanium or Ti6Al4V
(Elsevier, 2014) Souza, Júlio César Matias de; Henriques, Bruno; Ariza, Edith; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Silva, Filipe Samuel; Rocha, Luís A.; Celis, Jean-Pierre
The aim of this study was to evaluate the evolution of mechanical properties and chemical variation across veneering dental porcelain fused to different titanium-based substrates. Test samples were synthesized by fusing dental feldspar-based porcelain onto commercially pure titanium grade II or Ti6Al4V alloy. Samples were cross-sectioned at angles of 10 and 90° to the interface plane. Afterwards, nanoindentation tests and Scanning Electron Microscopy (SEM) imaging coupled to an Energy Dispersive Spectroscopy (EDS) system were carried out across interfaces extending from the metal towards the porcelain area. Elemental diffusion profiles across the porcelain-to-metal interfaces were also obtained by EDS analysis. The mismatch in mechanical properties found in porcelain-to-Ti6Al4V interfaces was lower than that of porcelain-to-CP titanium. Cracking was noticed at low-thickness veneering dental porcelain regions after the nanoindentation tests of samples cross-sectioned at low angles to the interface plane. A wide reaction zone between titanium and porcelain as well as higher incidence of defects was noticed at the porcelain-to-CP titanium interfaces. This study confirmed Ti6Al4V as an improved alternative to CP-titanium as it showed to establish a better interface with the veneering dental porcelain considering the slight chemical interaction and the lower mechanical properties mismatch. The elastic modulus of porcelain-to-Ti6Al4V samples showed to be less sensitive to porcelain thickness variations.
Mechanical properties of hot pressed CoCrMo alloy compacts for biomedical applications
(Elsevier, 2015) Henriques, Bruno; Bagheri, A.; Gasik, M.; Souza, J.C.M.; Carvalho, O.; Silva, F.S.; Nascimento, Rubens Maribondo do
This study aimed at investigating the influence of the processing conditions on the mechanical properties of hot pressed compacts of a CoCrMo biomedical alloy. Several hot pressed CoCrMo compacts were processed in vacuum (102 mbar), at a pressure of 60 MPa with different temperatures (900 C, 1000 C and 1100 C) and different times (10 min, 30 min and 60 min). Compacts were examined by SEM/EDS. The transverse rupture strength, Young’s Moduli and hardness were determined. The fracture surface of compacts were also examined. The compacts hot pressed at 900 C exhibited lower TRS than those processed at 1000 C and 1100 C, which showed similar strength values, regardless the sintering time. The 900 C compacts showed also lower YM and higher porosity. Lower hardness values were registered for 900 C compacts while 1000 C compacts exhibited the highest values. The fracture surface analyses revealed fragile fracture for 900 C compacts (10 min and 30 min) and 1000 C (10 min). The remaining compacts exhibited ductile fracture. A full characterization of the mechanical properties of hot pressed CoCrMo compacts has been made and the selection of the processing parameters according to the desired mechanical properties is now possible.
Mechanical strength and wear of dental glass-ionomer and resin composites affected by porosity and chemical composition
(Springer Link, 2015-08-13) Rodrigues, Daniela S.; Buciumeanu, Mihaela; Martinelli, Antonio Eduardo; Nascimento, Rubens Maribondo do; Henriques, Bruno; Silva, Filipe Samuel; Souza, Júlio César Matias de
The main aim of this study was to evaluate the influence of porosity, microstructure, and chemical composition on the wear and compressive strength of dental glass-ionomer or resin composite. Cylindrical samples (6 9 4 mm) were prepared from a nano-hybrid resin composite (GrandioSO/RC, VOCO), a resin-modified glass ionomer (VitremerTM/VI, 3 M-ESPE) and a conventional glass ionomer (IonofilMolar/CO, VOCO). Porosity and topography of the materials were evaluated by optical and scanning electron microscopy (SEM). Roughness was evaluated by Ra and Rt parameters at 0.1 mm/s under cutoff of 0.8 mm. Then, compressive tests were performed at 1 mm/min. Wear tests were carried out at 20 N, 2.5 mm of displacement, at 1 Hz for 90 min in artificial saliva solution. The results were statistically analyzed with a one-way ANOVA and Tukey’s test (p\0.05). Resin composite revealed a significantly lower porosity (1.21 ± 0.20 %) than glass-ionomer restoratives (5.69–7.54 %) as well as lower values of Ra and Rt roughness (p\0.05). Also, resin composite showed significantly higher values of mechanical strength (334 ± 15.9 MPa) compared to conventional (78.78 ± 13.30 MPa) or modified glass ionomer (169.50 ± 20.98 MPa) (p\0.05). For maximal depth of wear, resin composite also showed significantly lower values than glass ionomer (p\0.05). Homogeneous wear morphology was noticed by SEM analyses on glass ionomers in opposition to resin composite. Glass ionomers showed a poor mechanical behavior associated to a high porosity and wear rate when compared to resin composite.
On the mechanical properties and microstructure of zirconia-reinforced feldspar-based porcelain
(Elsevier, 2016-09) Nascimento, Rubens Maribondo do; Santos, Rafaela Luiz Pereira; Silva, Filipe Samuel; Motta, Fabiana Villela da; Henriques, Bruno; Souza, Júlio César Matias de
The aim of this study was to produce and to evaluate the mechanical properties of a dental feldspar-based porcelain reinforced by zirconia particles. The specimens were prepared by incorporating different volume fractions (10, 20, 30, 40 or 50%) of zirconia particles (3Y-TZP) in a porcelain matrix. The mixtures were hot pressed in vacuum at 970°C for 2 min. Flexural strength of the composites was measured using a three-point-bending test. Hardness, Young’s modulus and fracture toughness were also measured for all the composites. The microstructure and fracture surfaces were characterized by Field Emission Guns Scanning Electron Microscopy (FEG-SEM). Chemical analyses were performed by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The highest flexural strength (218 ± 24 MPa) and fracture toughness (2.1 ± 0.1 MPa m 1/2) values were recorded for composites containing 30% zirconia particles. That corresponded to improvement in mechanical properties of about 2 times relative to those registered for feldspar-based porcelain. It was not noticed any significant difference in hardness values. The Young’s moduli also increased with the addition of zirconia particles. The addition of zirconia particles to porcelain improved significantly the mechanical properties of the base material. Zirconia-reinforced porcelain can constitute a promising alternative to conventional feldspar-based porcelains to produce prosthetic restorations, mainly for posterior teeth where high strength and toughness are demanded
Physicochemical and microscopic characterization of implant–abutment joints
(Georg Thieme Verlag KG, 2018-01) Nascimento, Rubens Maribondo do; Lopes, Patricia A.; Carreiro, Adriana da Fonte Porto; Vahey, Brendan R.; Henriques, Bruno; Souza, Júlio César Matias de
The purpose of this study was to investigate Morse taper implant–abutment joints by chemical, mechanical, and microscopic analysis. Materials and Methods: Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun‐scanning electron microscopy (FEG‐SEM) before connection. The implant–abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant–abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant–abutment joints. Statistics: Results were statistically analyzed via one‐way analysis of variance, with a significance level of P < 0.05. Results: Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant–abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Conclusions: Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant–abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication
Shear bond strength of veneering porcelain to zirconia: Effect of surface treatment by CNC-milling and composite layer deposition on zirconia
(Elsevier, 2016-07) Nascimento, Rubens Maribondo do; Santos, Rafaela Luiz Pereira; Silva, Filipe Samuel; Souza, Júlio César Matias de; Motta, Fabiana Villela da; Carvalho, Oscar; Henriques, Bruno
Objectives: The purpose of this study was to evaluate the shear bond strength of veneering feldspathic porcelain to zirconia substrates modified by CNC-milling process or by coating zirconia with a composite interlayer. Methods: Four types of zirconia–porcelain interface configurations were tested: RZ – porcelain bonded to rough zirconia substrate (n1⁄416); PZ – porcelain bonded to zirconia substrate with surface holes (n1⁄416); RZI – application of a composite interlayer between the veneering porcelain and the rough zirconia substrate (n1⁄416); PZI – application of a composite interlayer between the porcelain and the zirconia substrate treated by CNC-milling (n1⁄416). The composite interlayer was composed of zirconia particles reinforced porcelain (30%, vol%). The mechanical properties of the ceramic composite have been determined. The shear bond strength test was performed at 0.5 mm/min using a universal testing machine. The interfaces of fractured and untested specimens were examined by FEG-SEM/EDS. Data was analyzed with Shapiro–Wilk test to test the assumption of normality. The one-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results (α1⁄40.05). Results: The shear bond strength of PZ (100715 MPa) and RZI (96711 MPa) specimens were higher than that recorded for RZ (control group) specimens (89715 MPa), although not significantly (p40.05). The highest shear bond strength values were recorded for PZI specimens (138719 MPa), yielding a significant improvement of 55% relative to RZ specimens (po0.05)
The effect of surface treatment on the friction and wear behavior of dental Y-TZP ceramic against human enamel
(Elsevier, 2017-12) Martinelli, Antonio Eduardo; Buciumeanu, Mihaela; Queiroz, José Renato Cavalcanti; Silva, Filipe Samuel; Henriques, Bruno
The aim of this paper was to study the influence of different surface treatments procedures on tribological behavior of Yttria-tetragonal zirconia polycristals (Y-TZP) against human enamel. The Y-TZP plates were divided into four areas and each area was subjected to a surface treatment according to the groups: GC - no surface treatment, GM – unidirectional milling with high speed tapered bur, GPK – polishing kit Kenda and GPD – polishing kit Diacera. The results demonstrated that the surface treatments play a relevant role on wear behavior of zirconia. In all cases the tooth suffered a greater wear than the Y-TZP plates. In the case of the polished groups it was obtained an improvement on the wear resistance of the tribopair
Tribological behaviour of glass-ceramics reinforced by Yttria Stabilized Zirconia
(Elsevier, 2016) Santos, Rafaela Luiz Pereira; Buciumeanu, Mihaela; Silva, Filipe Samuel; Souza, Júlio César Matias de; Nascimento, Rubens Maribondo do; Motta, Fabiana Villela da; Carvalho, Oscar; Henriques, Bruno
The aim of this study was to evaluate the tribological behaviour of a dental glass-ceramic (GC) reinforced by 20% (vol.) Yttria-Stabilized Zirconia. Two types of particles were tested: zirconia agglomerates (ZA) and pre-sintered zirconia particles (ZP). The wear tests were carried out using a ball-on-plate configuration. The wear mechanisms were characterized by field emission guns scanning electron microscope. Results revealed an improvement of wear behaviour for GC reinforced by ZP. The improvement on wear resistance was attributed to the effect of reinforcement, by the action of the uniformly distributed ZP that allowed the load transfer reinforcing mechanism through the matrix and reinforcement phase. Dental glass-ceramic reinforced by ZP can constitute a promising alternative to conventional glass-ceramics to produce prosthetic restorations
Wear of Morse taper and external hexagon implant joints after abutment removal
(Springer Science and Business Media LLC., 2017-03-20) Nascimento, Rubens Maribondo do; Prado, Abraão M.; Pereira, Jorge; Silva, Filipe S.; Henriques, Bruno; Benfatti, Cesar A. M.; López-López, José; Souza, Júlio César Matias de
The aim of this in vitro study was to evaluate the removal torque values on abutments and the morphological wear aspects of two different dental implant joints after immersion in a medium containing biofilm from human saliva. Twenty implant-abutment assemblies were divided into four groups in this study: (A) Morse taper free of medium containing biofilm, and (B) after contact with a medium containing biofilm from human saliva; (C) External Hexagon free of medium containing biofilm, and (D) after contact with medium containing biofilm from human saliva. The abutments were firstly torqued to the implants according to the manufacturer ́s recommendations, using a handheld torque meter. Groups B and D were immersed into 24 well-plates containing 2 ml BHI medium with microorganisms for 72 h at 37 °C under microaerophilic conditions. After detorque evaluation, the abutments were removed and the implants were analyzed by scanning electron microscopy (SEM) and profilometry. On the detorque evaluation, the torque values decreased for the external hexagon implants and increased for the Morse taper implants. However, the values were lower when both implantabutment assemblies were in contact with a medium containing biofilm from human saliva. The wear areas of contacting surfaces of the implants were identified by SEM. The highest average roughness values were recorded on the surfaces free of biofilm. The medium containing biofilm from human saliva affected the maintenance of the torque values on Morse taper and external hexagon abutments. Additionally, the removal of abutment altered the inner implant surfaces resulting in an increase of wear of the titanium-based connection

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Navegando por Autor "Henriques, Bruno"