Analysis of microleakage and marginal gap presented by new polymeric systems in class V restorations: An in vitro study.

OBJECTIVE: Evaluating the contraction of polymerization effect of silorane-based composite on dental interface in enamel. MATERIALS AND METHODS: Eighty class V cavities were confectioned in forty extracted molar teeth and restored with different combinations of resinous-based and bond system. They were divided into the following groups: (G1) three-step etch-and-rinse adhesive system and methacrylate-based resin, (G2) two-step etch-and-rinse adhesive system and methacrylate-based resin, (G3) Filtek P-90 self-conditioning adhesive system and methacrylate-based resin, (G4) Adper SE Plus self-conditioning adhesive system and methacrylate-based resin, (G5) three-step etch-and-rinse adhesive system and silorane-based resin, (G6) two-step etch-and-rinse adhesive system and silorane-based resin, (G7) Filtek P-90 self-conditioning adhesive system and silorane-based resin, (G8) Adper SE Plus self-conditioning adhesive system and silorane-based resin. RESULTS: Group 7 showed lower marginal leakage when compared with all other groups (p = 0.001). CONCLUSIONS: The results allows suggesting that silorane-based resinous system is adequate to promote more satisfactory marginal sealing than any other combination, since the system is combined with its own bond system.

Nanocrystalline cellulose as a reinforcing agent for electrospun polyacrylonitrile (PAN) nanofibers.

OBJECTIVES: Nanocrystalline cellulose (NCC) is a sustainable material with excellent mechanical properties and can potentially be used as a reinforcement agent. The objective of this work was to test the effects of NCC incorporation on the mechanical properties of electrospun polyacrylonitrile (PAN) nanofibers. METHODS: Eleven percent in weight of PAN (molecular weight 150 kD) in a dimethylformamide (DMF) solution was electrospun at 14.6 kV. Nonfunctionalized NCC was added to the solution at 1%, 2%, or 3 wt% (NCC/PAN). Suspensions were mixed and sonicated for 2 h before spinning. Strips (5 × 0.5 cm) were cut from the spun mat, parallel and perpendicular to the rotational direction of the fiber collection drum. Tensile tests were performed, and ultimate tensile strength (UTS), yield strength (YS; 0.3%), elastic modulus (E), and elongation at maximum stress (EMS, %) were calculated from stress-strain plots. Data were analyzed by multiple t tests and one-way ANOVA (α = 0.05). RESULTS: Among all groups, samples with 3 wt % NCC loading had significantly superior mechanical properties. The fiber mats showed anisotropic behavior. CONCLUSIONS: Regardless of concentration, the addition of NCC resulted in increased UTS, E, and YS of the nanofibers.

Effect of aging and testing method on bond strength of CAD/CAM fiber-reinforced composite to dentin.

OBJECTIVES: To evaluate and compare the outcomes of shear (S) and microtensile (µT) bond strength tests of CAD/CAM fiber-reinforced composite (FRC) to dentin. Aging with either fatigue or thermocycling were conducted for comparison with baseline microtensile group. METHODS: CAD/CAM FRC (Trinia, Bicon LLC, Boston, USA) blocks were milled to 3-mm diameter cylinders for shear and to blocks (5×5×5mm) for µT. Sixty extracted human molars were flattened to obtain dentin surfaces and randomly divided in four groups (n=15): (1) SC: samples tested in shear 24h after bonding; (2) µTC: samples tested in µT 24h after bonding); (3) µTF: samples submitted to mechanical fatigue prior to µT test, and; (4) µTT: thermocycling prior to µT test. Bonding system was applied onto the FRC material (Cera-Resin Bond, CRB, Shofu Dental, Kyoto, Japan). A conventional three-step adhesive system (All-bond 3, Bisco, Schaumburg, USA) was use with a self-cure resin cement (C&B resin cement, Bisco, Schaumburg, USA). Bond strength tests were conducted at 0.75mm/min and data analyzed using Weibull distribution (p<0.05). RESULTS: Weibull contour plots showed a significantly lower characteristic strength (η) and Weibull modulus (m) for SC (η=6.9MPa and m=1.4) compared to µTC (η=20.9MPa and m=4.5). Fatigued and thermocycled µT groups presented significantly reduced characteristic strength (η=3.1MPa and η=4.1MPa, respectively) compared to µTC. Weibull modulus was significantly reduced only for SC and µTF groups compared µTC. Failure predominantly occurred at the cement/FRC interface. SIGNIFICANCE: FRC bonded to dentin samples presented lower Weibull modulus and characteristic bond strength when immediately tested in shear compared to microtensile. Aging through thermocycling or mechanical fatigue significantly reduced the characteristic strength in microtensile testing, with the majority of failures emerging between restoration material and cement interface.

Influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic systems.

BACKGROUND: To evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces. MATERIAL AND METHODS: All-ceramic systems tested were lithium disilicate and zirconia veneered by layering technique. Sixty specimens (n=20) were subjected to shear bond strength. Ten of them were thermal and mechanical cycled. Fracture analysis was performed with stereomicroscopy and scanning electron microscopy. Energy dispersive X-ray spectroscopy analysis was performed across core/veneer interfaces. RESULTS: Thermal and mechanical cycling did not influence on bond strength. However, there was significant difference among systems (<0.01). CoCr group presented the highest values, followed by lithium disilicate, and zirconia. Failure modes were predominantly adhesive for CoCr, cohesive in core for lithium disilicate, and cohesive in veneer for zirconia. Energy dispersive X-ray showed interaction zone for CoCr and lithium disilicate groups and was inconclusive for zirconia. Fatigue had no influence on bond strength of groups tested. CONCLUSIONS: The results suggest that there is a chemical bond between core and veneer materials for CoCr and lithium disilicate groups. Key words:Ceramics, electron microscopy, fatigue, mechanical stress, shear bond strength.

Does hybridized dentin affect bond strength of self-adhesive resin cement?

BACKGROUND: Evaluate the influence of different hybridization bonding techniques of a self-adhesive resin cement. MATERIAL AND METHODS: 30 human health molars were divided into six groups (n=10). The specimens received three longitudinal sections, allowing insertion of central cuts in PVC matrices. Each group received a different dentin pretreatment according to the manufacturer's recommendations, except the control group (G1), as follows. G2 - a 3-step total-etch adhesive system (Optibond™ FL, Kerr); G3 - a 3-step total-etch adhesive system (Adper™ Scotchbond™ Multi-Purpose, 3M ESPE); G4 - a 2-step total-etch adhesive system (Adper™ Single Bond 2, 3M ESPE); G5 - a single-step self-etching system (Bond Force, Tokuyama); and G6 - universal bonding system (Single Bond Universal, 3M ESPE). Then, cylinders made of self-adhesive resin cement with polypropylene matrix was cemented in all groups (RelyX U200, 3M ESPE). Bond strength was assessed by submitting the specimens to micro-shear test and was characterized according to the fracture pattern observed through optical microscopy. RESULTS: The results were submitted to the Kruskal-Wallis test, which indicated a statistically significant difference between the groups (p=0.04), and Tukey's multiple comparisons, which indicated a statistically significant difference between G1 and G3 (p<0.05). The microscopic analysis revealed a high prevalence of adhesive failures, followed by mixed fractures, and cohesive failures in the dentin. CONCLUSIONS: The use of a previous dentin hybridization protocol is able to increase adhesive bonding resistance of self-adhesive resin cement, especially when used Adper™ Scotchbond™ Multi-Purpose system. Key words:Bonding, self-adhesive resin cement, adhesive systems, microshear.

Effect of silorane-based adhesive system on bond strength between composite and dentin substrate.

CONTEXT: The complexities of the oral environment, the dentin substrate, and the different bond and composite resin systems represent a challenge to the maintenance of reasonable bond between the composite resin and the tooth structure. AIMS: To evaluate the effect of the adhesive system on bond strength between silorane-based composite resin and dentin. MATERIALS AND METHODS: Fourteen human molars extracted were selected and vertically cut into 3 dentin fragments, randomly divided among the experimental groups and restored with Z250 and P90 composite resin using different adhesive protocols (Adper Single Bond 2, Silorano primer, Adper SE Plus, and Scotchbond Multiuse). Two composite resin cylinders were built up on each dentin surface (n = 10) and subjected to a micro-shear bond strength test. STATISTICAL ANALYSIS USED: Kruskal-Wallis one-way analysis of variance and Tukey test (P = 0.05). RESULTS: According to the results, Kruskal-Wallis test evidenced at least one statistical significant difference (P = 0.001). The Tukey test showed statistically significant differences among the group (P < 0.05). Group PSM8 (P90 + SM) showed statically significant higher results when compared with groups PSP4 (P90 + SP), PSB2 (P90 + SB), and ZSE5 (Z250 + SE). CONCLUSION: The results evidenced that the monomer of the adhesive system has an effect on bond strength between the composite resin and dentin.

Sintered anorganic bone graft increases autocrine expression of VEGF, MMP-2 and MMP-9 during repair of critical-size bone defects.

This study aimed to evaluate morphometrically the bone formation and immunohistochemically the expression of vascular endothelial growth factor (VEGF) and metalloproteinase (MMP)-2 and -9 during the healing of critical-size defects treated with sintered anorganic bone (sAB). The 8-mm diameter full-thickness trephine defects created in the parietal bones of rats were filled with sAB (test group) or blood clot (CSD-control group). At 7, 14, 21, 30, 90 and 180 days postoperatively (n = 6/period) the volume of newly formed bone and total number of immunolabeled cells (Ntm) for each protein were determined. Bone formation was smaller and faster in the CSD-control group, stabilizing at 21 days (6.74 mm(3)). The peaks of VEGF, MMP-2 and MMP-9 occurred at 7 and 14 days in fibroblasts and osteoblasts, with mean reduction of 0.80 time at 21 days, keeping constant until 180 days. In the test group, sAB provided continuous bone formation between particles throughout all periods. The peak of MMP-2 was observed at 7-14 days in connective tissue cells and for VEGF and MMP-9 at 30 days in osteoblasts and osteocytes. Ntm for VEGF, MMP-2 and MMP-9 were in average, respectively, 3.70, 2.03 and 5.98 times higher than in the control group. At 180 days, newly formed bone (22.9 mm(3)) was 3.74 times greater in relation to control. The physical and chemical properties of sAB allow increased autocrine expression of VEGF, MMP-2 and MMP-9, favoring bone formation/remodeling with very good healing of cranial defects when compared to natural repair in the CSD-control.

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements.

OBJECTIVE: The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resinmodified glass ionomer cements (RMGICs). MATERIAL AND METHODS: Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. RESULTS: Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. CONCLUSIONS: Except for Ionoseal, all cements provided satisfactory bond strength values.

Thermo and mechanical cycling and veneering method do not influence Y-TZP core/veneer interface bond strength.

OBJECTIVES: The purpose of this study was to evaluate the influence of thermal and mechanical cycling and veneering technique on the shear bond strength of Y-TZP (yttrium oxide partially stabilized tetragonal zirconia polycrystal) core-veneer interfaces. MATERIALS AND METHODS: Cylindrical Y-TZP specimens were veneered either by layering (n=20) or by pressing technique (n=20). A metal ceramic group (CoCr) was used as control (n=20). Ten specimens for each group were thermal and mechanical cycled and then all samples were subjected to shear bond strength in a universal testing machine with a 0.5mm/min crosshead speed. Mean shear bond strength (MPa) was analysed with a 2-way analysis of variance and Tukey's test (p<0.05). Failure mode was determined using stereomicroscopy and scanning electron microscopy (SEM). RESULTS: Thermal and mechanical cycling had no influence on the shear bond strength for all groups. The CoCr group presented the highest bond strength value (p<0.05) (34.72 ± 7.05 MPa). There was no significant difference between Y-TZP veneered by layering (22.46 ± 2.08 MPa) or pressing (23.58 ± 2.1 MPa) technique. Failure modes were predominantly adhesive for CoCr group, and cohesive within veneer for Y-TZP groups. CONCLUSIONS: Thermal and mechanical cycling, as well as the veneering technique does not affect Y-TZP core-veneer bond strength. CLINICAL SIGNIFICANCE: Different methods of veneering Y-TZP restorations would not influence the clinical performance of the core/veneer interfaces.

Prevalência de arcadas totalmente dentadas, totalmente edêntulas e parcialmente dentadas segundo classificação de Kennedy / Prevalence of edentulous and partially edentulous jaws according to Kennedy's classification

Poucos estudos estão disponíveis na literatura a respeito da prevalência de diferentes tipos de arcadas dentárias. Portanto, o objetivo deste estudo foi avaliar a prevalência dos tipos de arcadas dentárias em relação à presença de dentes através de radiografias panorâmicas. Foram avaliados 1.017 prontuários clínicos da Faculdade de Odontologia da Universidade do Sul de Santa Catarina, sendo 385 pacientes do gênero masculino e 632 do gênero feminino, totalizando 2.034 arcadas. Os resultados evidenciaram uma maior prevalência por arcadas parcialmente desdentadas (1.023 arcadas), das quais 743 (36,52%) eram do tipo Classe III de Kennedy, seguidas por 224 (11,99%) Classe I, 197 (9,68%) Classe II e 19 (0,93%) Classe IV. Observou-se ainda que destas 2.034 arcadas, 663 (32,59%) eram totalmente dentados e 168 (8,25%) eram totalmente desdentadas. Conclui-se que as arcadas parcialmente desdentadas são mais prevalentes, seguidas pelas totalmente dentadas e, com menor prevalência, pelas totalmente desdentadas. Foi observada uma maior prevalência de espaços protéticos na mandíbula em relação à maxila (AU).

Few studies about the prevalence of different types of dental arches are available in the literature. So the objective of this study was to evaluate the prevalence of dental arches types in relation to the presence of teeth through panoramic radiographic examination. Clinical records of 1017 patients of the Dental School of the Universidade do Sul de Santa Catarina were evluated (385 male and 632 female), totalizing 2034 dental arches. Results showed a greater prevalence of partially edentulous jaws (1.023), of which 743 (36,52%) were Kennedy Class III, followed by 224 (11.99%) Class I, 197 (9,68%) Class II and 19 (0,93%) Class IV. It was also observed that of 2034 dental arches, 663 (32.59%) had all the teeth remaining and 168 (8.25%) were totally edentulous. It was concluded that the partially edentulous dental arches are more prevalent, followed by those which had all teeth, and with less prevalence the totally edentulous dental arches. It was also observed a higher prevalence of prosthetic spaces in the mandible compared to the maxilla (AU).

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements

OBJECTIVE: The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resinmodified glass ionomer cements (RMGICs). MATERIAL AND METHODS: Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. RESULTS: Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. CONCLUSIONS: Except for Ionoseal, all cements provided satisfactory bond strength values. .

Análise de resistência à tração de pinos de fibra de vidro cimentados com diferentes cimentos de ionômero de vidro através do teste pull-out / Evaluation of tensile strength of fiberglass posts cemented with different glass ionomer cements through pull-out-test

Para que se consiga resistência e retenção de pinos intrarradiculares é essencial a adequada seleção do agente cimentante. Objetivo: analisar diferentes tipos de cimento de ionômero de vidro utilizados na cimentação de pinos intrarradiculares de fibra de vidro, o método através do teste de resistência à tração pull-out. Métodos: Foram cimentados pinos de fibra de vidro em 50 caninos humanos, divididos nos seguintes grupos (n = 10): Grupo I ? Ionoseal (Voco), Grupo II ? Lining and Cement (GC), Grupo III ? Fuji II Improved (GC), Grupo IV ? Rely X Luting 2 (3M Espe), Grupo V ? Ketac Cem (3M Espe). Resultados: o teste Anova mostrou diferença significativa entre os grupos. O teste de Tukey mostrou que o Lining and Cement foi estatisticamente mais resistente que o Ionoseal (p < 0,05). Conclusão: assim, analisando-se os resultados, pode-se concluir que avaliando a resistência à tração dos pinos de fibra de vidro cimentados com diferentes cimentos de ionômero de vidro através do teste pull-out o cimento de ionômero de vidro convencional Lining and Cement se mostrou superior aos outros cimentos.

O papel da concentração de nanofibras e da composição da matriz resinosa nas propriedades flexurais de compósitos experimentais baseados em nanofibras / Flexural properties of experimental nanofiber reinforced composite are affected by resin composition and nanofiber/resin ratio

O objetivo do presente estudo foi de avaliar a influência de soluções de resina com diferentes proporções de monômeros e diferentes concentrações em massa de nanofibras nas propriedades flexurais de compósitos resinosos experimentais reforçados com nanofibras de poliacrilonitrila (PAN). Materiais e métodos: Nanofibras de PAN foram produzidas pelo processo de eletrofiação e caraterizadas por teste de tração e microscopia eletrônica de varredura (MEV). Os compósitos experimentais foram produzidos pela infiltração das mantas de nanofibras com diferentes misturas de BisGMA-TEGDMA (BisGMA/TEGDMA: proporções em % massa de 30/70, 50/50, e 70/30). Foram incorporadas diferentes concentrações em massa de nanofibras (de 0% a 8%). Espécimes em forma de barra foram seccionados a partir de blocos do compósito experimental e armazenados em água na temperatura de 37oC por 24h anteriormente à realização dos testes de flexão de três pontos. Foram avaliados a resistência flexural (RF), o módulo flexural (MF) e o trabalho de fratura (TF). Resultados: Os testes de tração das nanofibras de PAN demonstraram um comportamento anisotrópico das mantas de nanofibras. As propriedades mecânicas exibiram maiores valores na direção perpendicular ao eixo de rotação do coletor metálico utilizado na produção das fibras por eletrofiação. Maiores proporções de BisGMA nas misturas de resina resultaram em maiores valores de RF e MF, o que não ocorreu para os valores de TF. A adição de diferentes concentrações de nanofibras não afetou as propriedades de RF e MF em comparação com o grupo controle (resina pura) (p>0.05). No entanto, a adição das nanofibras promoveu um aumento significante do TF, principalmente para as misturas de resina com maior proporção de TEGDMA (p<0,05). Significância: A inclusão de nanofibras de PAN em resinas de modo a formar compósitos resinosos reforçados por nanofibras não afetou negativamente as propriedades flexurais do material e resultou em um aumento significativo da...

The present study had the objectives to evaluate the influence of different resin blends concentrations and nanofibers mass ratio on flexural properties of experimental Poliacrylonitrile (PAN) nanofibers reinforced composite. Materials and Methods: Poliacrylonitrile (PAN) nanofibers mats were produced by electrospinning and characterized by tensile testing and scanning electron microscopy (SEM). Experimental resin-fiber composite beams were manufactured by infiltrating PAN nanofiber meshs with varied concentrations of BisGMA-TEGDMA resin blends (BisGMA/TEGDMA: 30/70, 50/50 and 70/30 weight %). The mass ratio of fiber to resin varied from 0% to 8%. Beams were cured and stored in water at 37oC. Flexural strength (FS), flexural modulus (FM) and work of fracture (WF) were evaluated by three-point bending test after 24 hs storage. Results: The tensile properties of the PAN nanofibers indicated an anisotropic behavior being always higher when tested in a direction perpendicular to the rotation of the collector drum. Except for WF, the other flexural properties (FS and FM) were always higher as the ratio of BisGMA to TEGDMA increased in the neat resin beams. The addition of different ratios of PAN fibers did not affect FS and FM of the composite beams as compared to neat resin beams (p>0.05). However, the addition of fibers significantly increased the WF of the composite beams, and this was more evident for the blends with higher TEGDMA ratios (p<0.05). Significance: The inclusion of PAN nanofibers into resin blends did not negatively affect the properties of the composite and resulted in an increase in toughness that is a desirable property for a candidate material for restorative application.

O papel da concentração de nanofibras e da composição da matriz resinosa nas propriedades flexurais de compósitos experimentais baseados em nanofibras / Flexural properties of experimental nanofiber reinforced composite are affected by resin composition and nanofiber/resin ratio

O objetivo do presente estudo foi de avaliar a influência de soluções de resina com diferentes proporções de monômeros e diferentes concentrações em massa de nanofibras nas propriedades flexurais de compósitos resinosos experimentais reforçados com nanofibras de poliacrilonitrila (PAN). Materiais e métodos: Nanofibras de PAN foram produzidas pelo processo de eletrofiação e caraterizadas por teste de tração e microscopia eletrônica de varredura (MEV). Os compósitos experimentais foram produzidos pela infiltração das mantas de nanofibras com diferentes misturas de BisGMA-TEGDMA (BisGMA/TEGDMA: proporções em % massa de 30/70, 50/50, e 70/30). Foram incorporadas diferentes concentrações em massa de nanofibras (de 0% a 8%). Espécimes em forma de barra foram seccionados a partir de blocos do compósito experimental e armazenados em água na temperatura de 37oC por 24h anteriormente à realização dos testes de flexão de três pontos. Foram avaliados a resistência flexural (RF), o módulo flexural (MF) e o trabalho de fratura (TF). Resultados: Os testes de tração das nanofibras de PAN demonstraram um comportamento anisotrópico das mantas de nanofibras. As propriedades mecânicas exibiram maiores valores na direção perpendicular ao eixo de rotação do coletor metálico utilizado na produção das fibras por eletrofiação. Maiores proporções de BisGMA nas misturas de resina resultaram em maiores valores de RF e MF, o que não ocorreu para os valores de TF. A adição de diferentes concentrações de nanofibras não afetou as propriedades de RF e MF em comparação com o grupo controle (resina pura) (p>0.05). No entanto, a adição das nanofibras promoveu um aumento significante do TF, principalmente para as misturas de resina com maior proporção de TEGDMA (p<0,05). Significância: A inclusão de nanofibras de PAN em resinas de modo a formar compósitos resinosos reforçados por nanofibras não afetou negativamente as propriedades flexurais do material e resultou em um aumento significativo da...

The present study had the objectives to evaluate the influence of different resin blends concentrations and nanofibers mass ratio on flexural properties of experimental Poliacrylonitrile (PAN) nanofibers reinforced composite. Materials and Methods: Poliacrylonitrile (PAN) nanofibers mats were produced by electrospinning and characterized by tensile testing and scanning electron microscopy (SEM). Experimental resin-fiber composite beams were manufactured by infiltrating PAN nanofiber meshs with varied concentrations of BisGMA-TEGDMA resin blends (BisGMA/TEGDMA: 30/70, 50/50 and 70/30 weight %). The mass ratio of fiber to resin varied from 0% to 8%. Beams were cured and stored in water at 37oC. Flexural strength (FS), flexural modulus (FM) and work of fracture (WF) were evaluated by three-point bending test after 24 hs storage. Results: The tensile properties of the PAN nanofibers indicated an anisotropic behavior being always higher when tested in a direction perpendicular to the rotation of the collector drum. Except for WF, the other flexural properties (FS and FM) were always higher as the ratio of BisGMA to TEGDMA increased in the neat resin beams. The addition of different ratios of PAN fibers did not affect FS and FM of the composite beams as compared to neat resin beams (p>0.05). However, the addition of fibers significantly increased the WF of the composite beams, and this was more evident for the blends with higher TEGDMA ratios (p<0.05). Significance: The inclusion of PAN nanofibers into resin blends did not negatively affect the properties of the composite and resulted in an increase in toughness that is a desirable property for a candidate material for restorative application.

Influência da ciclagem térmica e mecânica em água na resistência ao cisalhamento da união infraestrutura/porcelana de cobertura de diferentes sistemas totalmente cerâmicos / Shear bond strength of all-ceramics core/veneer interface and its susceptibility to thermal and mechanical cycling

Este estudo avaliou a influência da ciclagem térmica e mecânica, aliadas, na resistência ao cisalhamento da interface entre porcelana de cobertura e infraestruturas de diferentes sistemas totalmente. Também foi realizada a caracterização das interfaces por meio de análise de espectroscopia por energia dispersiva de Raios X (EDS). Foram testados sistemas totalmente cerâmicos a base de dissilicato de lítio (DL), zircônia tetragonal estabilizada por ítrio recoberta por estratificação (ZC) e por injeção (ZI) e alumina infiltrada por vidro (AI). Um grupo metalocerâmico a base de liga de CoCr foi testado como grupo controle. Vinte espécimes circulares de 6mm de diâmetro de cada sistema foram submetidos ao teste de resistência ao cisalhamento em máquina de ensaios mecânicos, sendo que metade destes (n=10) sofreram os procedimentos de ciclagem térmica e mecânica antes da realização dos testes. Os resultados foram analisados através do teste ANOVA a dois critérios (p<0,05) e utilizou-se teste de Tukey (p<0,05) para as comparações múltiplas. Análise das fratura foi realizada através de estereomicroscópio e MEV. A análise de EDS foi realizada ao longo da interface infraestrutura/porcelana de cobertura em um espécime de cada sistema seccionado longitudinalmente. As ciclagens térmica e mecânica aliadas não influenciaram na resistência ao cisalhamento dos sistemas testados. Houve, contudo, diferença estatística entre os sistemas testados. O grupo CoCr apresentou os maiores valores (34,72 ± 7,05 Mpa), seguido dos grupos DL (27,07 ± 5,28), ZI (23,58 ± 2,71), ZC (22,46 ± 2,08) e AI (18,15 ± 1,99). Os modos de fratura foram predominantemente adesivos para o grupo CoCr, coesivos na infraestrura para o grupo DL, coesivo na porcelana de cobertura para os grupos ZC e ZI, e mistos para o grupo AI. As análises de EDS mostraram haver uma zona de interação para todos os sistemas testados. Deste modo, é possível sugerir, através das análises de fratura e de EDS,...

The objective of this study was to evaluate the influence of thermal and mechanical cycling on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces. It was also to characterize chemically the interfaces by energy dispersive spectroscopy (EDS). The allceramic systems tested were lithium dissilicate (DL), zirconia veneered by layering technic (ZC) or pressing technic (ZI) and glass infiltrated alumina (AI). A CoCr group was used as control. Twenty cylindrical specimens for each system were subjected to shear bond strength in a universal testing machine with a 0.5 mm/min crosshead speed. Half of the specimens (n=10) were thermal and mechanical cycled before shear bond strength was carried out. Mean shear bond strength (MPa) were analyzed with a 2-way analysis of variance and the Tukey test. Failures were classified with tereomicroscope and scanning electron microscope (SEM) analysis. In an addition, energy dispersive X-ray spectroscopy (EDS) analysis was performed from core/veneer interfaces. Thermal and mechanical cycling did not influence statistically on the shear bond strength for the systems evaluated. However, there was a statically significant difference between the systems evaluated. Control group (CoCr) presented the highest values (34,72 ± 7,05 Mpa), followed by DL (27,07 ± 5,28), ZI (23,58 ± 2,71), ZC (22,46 ± 2,08) e AI (18,15 ± 1,99). Thermal and mechanical cycling did not influence statistically on the shear bond strength for the systems evaluated. Failure modes were predominantly adhesive for CoCr group, cohesive in the core for DL, cohesive in veneer for groups ZC and ZI and mixed for AI. EDS analysis showed a interaction zone for all systems evaluated. Thus, it is possible to suggest, trough EDS analysis, that there is a chemical bond between core and veneer materials and that the shear bond strength variations can be related to intrinsic factors within veneering porcelain or to its wetting capacity.