Effect of the surface treatment of plain carbon fiber posts on the retention of the composite core: an in vitro evaluation

Foi avaliado o possível efeito de tratamentos superficiais em pinos de fibra de carbono lisos, quando comparados aos pinos serrilhados, na retenção à resina composta empregada na confecção de núcleos de preenchimento. Foram utilizados cinqüenta pinos de fibra de carbono, divididos em cinco grupos: os quatro primeiros grupos eram constituídos por pinos do tipo liso, cujas superfícies foram tratadas, e o último grupo por dez pinos do tipo serrilhado. Foram desenvolvidas matrizes de resina acrílica com um leito ajustado para conter o pino, com um alargamento na porção coronária para posterior preenchimento com resina composta. Após o tratamento superficial, todos os pinos receberam camadas de primer, foram secos e então ajustados à matriz de resina, colocando-se a resina composta autopolimerizável na porção coronária para um núcleo de preenchimento de 3 mm. As amostras foram submetidas a termociclagem e armazenadas em água destilada por uma semana. Os espécimes foram testados por meio de ensaios mecânicos de tração, à velocidade de 0,5 mm/min, até o deslocamento do conjunto ou a fratura da resina do núcleo. As conclusões foram as seguintes: a) o tratamento superficial nos grupos tratados por meio de jateamento (Grupo A), pontas diamantadas marcadoras de profundidade para facetas laminadas (Grupo C) e alteração da morfologia da extremidade coronária (Grupo D) conferiu aos pinos lisos valores de retenção comparáveis aos dos pinos serrilhados (Grupo E) nos ensaios de tração, porém sem diferença estatisticamente significativa entre estes grupos; b) os pinos tratados por meio de pontas diamantadas de granulação média (Grupo B) obtiveram valores de retenção menores que os demais grupos.

Flexural Strength of Four Adhesive Fixed Dental Prostheses of Composite Resin Reinforced with Glass Fiber

Purpose: To evaluate the flexural strength of two fixed dental prosthesis (FDP) designs simulating frameworks of adhesive fixed partial prostheses, reinforced or not by glass fiber.Materials and Methods: Forty specimens, made with composite resin, were divided into 4 groups according to the framework design and the presence of fiber reinforcement: A1 - occlusal support; A2: occlusal support + glass fiber; B1: occlusal and proximal supports; B2: occlusal and proximal supports + glass fiber. The specimens were subjected to the three-point bending test, and the data were submitted to two-way ANOVA and Tukey's test (5%).Results: Group A2 (97.9 +/- 38 N) was statistically significantly different from all other experimental groups, presenting a significantly lower mean flexural strength.Conclusion: The use of glass fibers did not improve the flexural strength of composite resin, and designs with occlusal and proximal supports presented better results than designs simulating only occlusal support.

Effect of Static and Cyclic Loading on Ceramic Laminate Veneers Adhered to Teeth with and Without Aged Composite Restorations

Purpose: Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses. The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations.Materials and Methods: Eighty sound maxillary incisors were collected and randomly divided into four groups: group 1: control group, no restorations; group 2: two Class III restorations; group 3: two Class IV restorations; group 4: complete composite substrate. Standard composite restorations were made using a microhybrid resin composite (Anterior Shine). Restored teeth were subjected to thermocycling (6000 cycles). Window preparations were made on the labial surface of the teeth for ceramic laminate fabrication (Empress II). Teeth were conditioned using an etch-and-rinse system. Existing composite restorations representing the aged composites were silica coated (CoJet) and silanized (ESPE-Sil). Ceramic laminates were cemented using a bis-GMA-based cement (Variolink Veneer). The specimens were randomly divided into two groups and were subjected to either static (groups 1a, 2a, 3a, 4a) or cyclic loading (groups 1b, 2b, 3b, 4b). Failure type and location after loading were classified. Data were analyzed using one-way ANOVA and Tukey's test.Results: Significantly higher fracture strength was obtained in group 4 (330 +/- 81 N) compared to the controls in group 1 (179 +/- 120 N) (one-way ANOVA, p < 0.05). Group lb survived a lower mean number of cyclic loads (672,820 cycles) than teeth of groups 2b to 4b (846x10(3) to 873x10(3) cycles). Failure type evaluation after the fracture test showed predominantly adhesive failures between dentin and cement, but after cyclic loading, more cohesive fractures in the ceramic were seen.Conclusion: Ceramic laminate veneers bonded to conditioned aged composite restorations provided favorable results. Surface conditioning of existing restorations may eliminate the necessity of removing aged composite restorations.

Fracture resistance of endodontically treated teeth with different heights of crown ferrule restored with prefabricated carbon fiber post and composite resin core by intermittent loading

This study evaluated the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber posts and varying quantities of coronal dentin. Sixty freshly extracted upper canines were randomly divided into groups of 10 teeth each. The specimens were exposed to 250,000 cycles in a controlled chewing simulator. All intact specimens were subjected to a static load (N) in a universal testing machine at 45 degrees to the long axis. Data were analyzed by 1-way analysis of variance and Tukey test (alpha = .05). Significant differences (P < .001) were found among the mean fracture forces of the test groups (positive control, 0 mm, 1 mm, 2 mm, 3 mm, and negative control groups: 1022.82 N, 1008.22 N, 1292.52 N, 1289.19 N, 1255.38 N, and 1582.11, respectively). These results suggested that the amount of coronal dentin did not significantly increase the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber post and composite resin core. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e52-e57)

Interfacial fracture of dentin adhesively bonded to quartz-fiber reinforced composite

The paper presents the results of an experimental study of interfacial failure in a multilayered structure consisting of a dentin/resin cement/quartz-fiber reinforced composite (FRC). Slices of dentin close to the pulp chamber were sandwiched by two half-circle discs made of a quartz-fiber reinforced composite, bonded with bonding agent (All-bond 2, BISCO, Schaumburg) and resin cement (Duo-link. BISCO, Schaumburg) to make Brazil-nut sandwich specimens for interfacial toughness testing. Interfacial fracture toughness (strain energy release rate, G) was measured as a function of mode mixity by changing loading angles from 0 degrees to 15 degrees. The interfacial fracture surfaces were then examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) to determine the failure modes when loading angles changed. A computational model was also developed to calculate the driving forces, stress intensity factors and mode mixities. Interfacial toughness increased from approximate to 1.5 to 3.2 J/m(2) when the loading angle increases from approximate to 0, 0 to 15 degrees. The hybridized dentin/cement interface appeared to be tougher than the resin cement/quartz-fiber reinforced epoxy. The Brazil-nut sandwich specimen was a suitable method to investigate the mechanical integrity of dentin/cement/FRC interfaces. (C) 2011 Elsevier B.V. All rights reserved.

Bond strength durability of a resin composite on a reinforced ceramic using various repair systems

Objectives. This study compared the durability of repair bond strength of a resin composite to a reinforced ceramic after three repair systems.Methods. Alumina-reinforced feldspathic ceramic blocks (Vitadur-alpha(R)) (N=30) were randomly divided into three groups according to the repair method: PR-Porcelain Repair Kit (Bisco) [etching with 9.5% hydrofluoric acid + silanization + adhesive]; CJ-CoJet Repair Kit (3M ESPE) [(chairside silica coating with 30 mu m SiO2 + silanization (ESPE(R)-Sil) + adhesive (Visio(TM)-Bond)]; CL-Clearfil Repair Kit [diamond surface roughening, etching with 40% H3PO4 + Clearfil Porcelain Bond Activator + Clearfil SE Bond)]. Resin composite was photo-polymerized on each conditioned ceramic block. Non-trimmed beam specimens were produced for the microtensile bond strength (mu TBS) tests. In order to study the hydrolytic durability of the repair methods, the beam specimens obtained from each block were randomly assigned to two conditions. Half of the specimens were tested either immediately after beam production (Dry) or after long-term water storage (37 degrees C, 150 days) followed by thermocyling (12,000 cycles, 5-55 degrees C) in a universal testing machine (1 mm/min). Failure types were analyzed under an optical microscope and SEM.Results. mu TBS results were significantly affected by the repair method (p=0.0001) and the aging conditions (p=0.0001) (two-way ANOVA, Tukey's test). In dry testing conditions, PR method showed significantly higher (p < 0.001) repair bond strength (19.8 +/- 3.8 MPa) than those of CJ and CL (12.4 +/- 4.7 and 9.9 +/- 2.9, respectively). After long-term water storage and thermocycling, CJ revealed significantly higher results (14.5 +/- 3.1 MPa) than those of PR (12.1 +/- 2.6 MPa) (p < 0.01) and CL (4.2 +/- 2.1 MPa) (p < 0.001). In all groups when tested in dry conditions, cohesive failure in the composite accompanied with adhesive failure at the interface (mixed failures), was frequently observed (76%, 80%, 65% for PR, CJ and CL, respectively). After aging conditions, while the specimens treated with PR and CJ presented primarily mixed failure types (52% and 87%, respectively), CL group presented mainly complete adhesive failures at the interface (70%).Significance. Hydrolytic stability of the repair method based on silica coating and silanization was superior to the other repair strategies for the ceramic tested. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of Carbamide Peroxide Bleaching Gel Concentration on the Bond Strength of Dental Substrates and Resin Composite

Purpose: This study evaluated the effect of bleaching gel containing 10%, 15% and 20% carbamide peroxide (CP) on the bond strength of dental enamel or dentin and resin composite restorations.Methods: The buccal surfaces of 12 bovine tooth crowns were conditioned with 37% phosphoric acid, and the adhesive resin Single Bond 2 and the resin composite Filtek Z350 were used to perform the restorations. The blocks were sectioned to obtain bar specimens. Each specimen group (enamel-E, dentin-D) was divided into four subgroups (n=15): S-artificial saliva; 10-10% CP bleaching; 15-15% CP bleaching; 20-20% CP bleaching. CP was applied for six hours daily for two weeks. The specimens were submitted to the a test in a universal testing machine. The data were analyzed by one-way ANOVA and the Tukey post-hoc test and a correlation analysis (r) was performed.Results: For Group E, the mean value (+/- standard-deviation) was 21.86 (+/- 6.03)a, 18.91 (+/- 8.31)ab, 15.43 (+/- 7.44)b and 10.6 (+/- 4.94)c for ES, E10, E15 and E20, respectively. For Group D, the alpha values were 34.73 (+/- 4.68)a, 35.12 (+/- 13.43)a, 29.67 (+/- 6.84)ab and 24.56 (+/- 6.54)b for DS, D10, D15 and D20, respectively. A negative correlation between the CP concentration and mean values was observed for both the enamel (r=-0.95) and dentin (r=-0.85) groups.Conclusion: In the current study, the bond strength of the restoration to enamel and the restoration to dentin were influenced by the application of CP and was dependent on the CP concentration in the bleaching gel.

A retrospective look at esthetic resin composite and glass-ionomer Class III restorations: A 2-year clinical evaluation

Objective: A restorative material for Class III cavities must, besides being functional, be esthetically satisfactory, providing good working conditions and several shade and color options. A clinical evaluation was initiated to compare the suitability of resin composite and glass-ionomer cement materials for such restorations.Method and materials: Forty-two Class III conservative cavities, esthetically important because of facial extensions, were selected. Resin composite restorations were placed in 21 cavities, and the remaining 21 were restored with glass-ionomer cement. The following characteristics were studied: color or-esthetics, anatomic shape, surface texture, staining, marginal infiltration, dental plaque retention, and occurrence of fracture. After 24 months, the restorations were evaluated.Results: the only statistically significant difference between the resin composite and glass-ionomer cement restorations in the experimental period involved color or esthetics.Conclusion: Resin composites and glass-ionomer materials provide excellent functional and esthetic results in Class III cavities when properly indicated.

Effect of antioxidant agents on bond strength of composite to bleached enamel with 38% hydrogen peroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)