Influence of Specimen Dimension, Water Immersion Protocol, and Surface Roughness on Water Sorption and Solubility of Resin-Based Restorative Materials.

The evaluation of water sorption and solubility is pivotal for the development of new resin-based restorative materials with the potential for clinical application. The purpose of the present study was to evaluate the influence of the specimen dimension, water immersion protocol, and surface roughness on the water sorption and solubility of three resin-based restorative materials. Disk-shaped specimens of 15 mm × 1 mm, 10 mm × 1 mm, and 6 mm × 1 mm were produced with a composite resin (Z100), a resin cement (RelyX ARC), and an adhesive system (Single Bond 2-SB2). The specimens were immersed in distilled water according to four protocols: ISO (all the specimens for each group were vertically immersed in 50 mL); IV-10 (the specimens were individually and vertically immersed in 10 mL); IH-10 (the specimens were individually and horizontally immersed in 10 mL); and IH-2 (the specimens were individually and horizontally immersed in 2 mL). The surface roughness (Sa and Sp) was evaluated using an atomic force microscope, and the degree of conversion was determined using FT-IR spectrometry. The specimen dimension and water immersion protocol had no effect on water sorption and solubility. For the three resin-based restorative materials, Sp was higher than Sa. The degree of conversion was not influenced by the specimen dimension. The variations in the specimen dimension and water immersion protocol compared to those determined by ISO 4049 did not prevent the comparison between the values of water sorption and solubility obtained for a given resin-based restorative material.

The Influence of Adhesive Strategy, Type of Dental Composite, and Polishing Time on Marginal Gap Formation in Class I-like Cavities.

Even after more than six decades of dental composite invention (1962), there is still controversial information about the time in which composite restorations should be polished in order to avoid marginal gap formation at the tooth-composite interface. The aim of the present study was to analyze the influence of adhesive strategy, the type of dental composite, and polishing time on marginal gap formation (%MG) at the tooth-composite interface. Class I-like cavities were hybridized with a universal adhesive system (Single Bond Universal) through two strategies: selective enamel etching (SEE) or self-etching mode (SEM). Cavities were filled with two types of dental composites: nanofilled (Z350) or bulk fill (Filtek One Bulk Fill-ONE), and polishing was performed immediately or delayed for 7 days (n = 5). %MG was evaluated by using a 3D laser confocal microscope. As flexural modulus (FM) and degree of conversion (DC%) are determinants of marginal integrity in dental composite restorations, these properties were evaluated for both composites. Data were analyzed by ANOVA and Tukey's HSD test (α = 0.05). Cavities hybridized following the SEE strategy presented lower %MG (p < 0.05). Z350 showed higher %MG than ONE (p < 0.05). There was no difference in %MG between the polishing times when the SEE strategy was used (p > 0.05). Z350 presented higher FM than ONE (p < 0.05). DC% was found to be not significant (p > 0.05). The results suggest that selective enamel etching (SEE) is a better strategy for producing less %MG in composite restorations with enamel margins irrespective of the time in which the restoration is polished.

Formação de fendas em restaurações de resina composta: polimento imediato versus tardio / Gap formation in composite resin restorations: immediate versus late polishing

O objetivo deste estudo foi avaliar a influência do momento da etapa de polimento, imediato ou após sete dias, na formação de fendas em restaurações de resina composta. Cavidades cilíndricas foram preparadas nas superfícies vestibulares de incisivos bovinos. Cada cavidade foi hibridizada com um dos dois sistemas adesivos: convencional (Adper Single Bond 2) ou autocondicionante (Single Bond Universal), e restaurada usando uma das três resinas compostas: nanoparticulada (Z350), micro-híbrida (P60) e bulk-fill (ONE). As cavidades restauradas foram divididas em dois subgrupos de acordo com o tempo de polimento, imediato ou postergado por 7 dias após a restauração. Por meio da combinação dos sistemas adesivos, resinas compostas e tempos de polimento, foram criados 12 grupos (n = 5). As porcentagens de fendas marginais (%FM) foram avaliadas quantitativamente com o microscópio confocal de varredura a laser. O módulo de elasticidade das resinas compostas foi obtido por meio do teste de flexão em três pontos. Os dados foram analisados por análise de variância e pelo teste de Tukey's HDS (α = 0,05). Em relação ao sistema adesivo, a %FM foi estatisticamente maior para as cavidades restauradas com Single Bond Universal (p<0,05). Com relação às resinas compostas, o resultado foi o seguinte: P60 > ONE > Z350 (p<0,05). O tempo de polimento imediato apresentou %FM estatisticamente menor que o tardio (p<0,05). P60 apresentou o maior módulo de elasticidade (p<0,05). Foi possível concluir que o polimento imediato gera menor formação de fendas em restaurações de resina composta. (AU)

The aim of this study was to analyze the influence of the polishing time, immediately or after seven days, in gap formation in composite resin restorations. Cylindrical cavities were prepared on buccal surfaces of bovine incisors. Each cavity was hybridized with one of the two adhesive systems: etch-and-rinse (Adper Single Bond 2) and self-etching (Single Bond Universal), and restored using one of the three composite resins: nanofilled (Z350), minifilled hybrid (P60) and bulk-fill (ONE). The cavities restored were divided in two subgroups according to polishing time, immediately or delayed by 7 days after specimen restoration. Through the combination of the adhesive systems, composite resins and polishing times, 12 groups were created (n=5). Percentages of marginal gaps (%MG) were quantitatively assessed with confocal laser scanning microscope. The flexural modulus of the composite resins was obtained from bar-shaped specimens submitted to three-point bending test. The data were analyzed by three-way ANOVA and Tukey's HSD test (α=0.05). Regarding adhesive system, %MG was statistically higher for cavities restored with Single Bond Universal (p<0.05). With respect to composite resins, the result was as follow: P60 > One > Z350 (p<0.05). Immediate polishing time presented statistically lower %MG than delayed one (p<0.05). P60 presented the highest flexural modulus (p<0.05). It was possible to conclude that immediate polishing generates less gap formation in composite resin restorations. (AU)

Restoration of an amalgam-stained thooth with Bulk-Fill composite resin: a case report

Introdution: Recently, composite resins that have low shrinkage and low polymerization stress have been released, the so-called Bulk-Fill composites. These offer the dental surgeon the possibility of inserting increments of up to 4 mm, making the restorative procedure faster. Objective : to report a clinical case of a posterior tooth restoration with discolored dentin substrate using a medium viscosity Bulk-Fill composite resin associated with an opacifying agent. Case report: upon clinical and radiographic examination, a 50-year-old male patient was informed about the need to replace the defective silver amalgam restoration on the occlusal surface of tooth 16. The unsatisfactory restoration was removed and then the bonding technique was performed to restore the cavity using a two-step self-etching adhesive (AdheSE, Ivoclar Vivadent, Schann, Liechtenstein). Due to the discolored dentin substrate, an opacifying agent (IPS Empress Direct Opaque, Ivoclar Vivadent, Schann, Liechtenstein) was applied to the bottom of the cavity, and then was photoactivated for 40 s. The restoration was performed with a single increment of Bulk-Fill resin composite (Tetric N-Ceram Bulk-Fill IVB, Ivoclar Vivadent, Schann, Liechtenstein) that was photoactivated for 40 s. The finishing and polishing procedures were performed using abrasive rubbers. Result: at the end, an aesthetically satisfactory restoration was obtained with the aid of the opacifying agent. Conclusion: it is possible to perform restorations faster with medium viscosity Bulk-Fill composites. However, as it is an essentially translucent material, the use of an opacifying agent in discolored tooth substrate is recommended, in order to obtain an aesthetically satisfactory result.

Introdução: Recentemente, foram lançadas no mercado resinas compostas que apresentam baixa contração e baixa tensão de polimerização, as chamadas resinas compostas Bulk-Fill. Estas oferecem ao cirurgião-dentista a possibilidade de inserir incrementos de até 4 mm, tornando o procedimento restaurador mais rápido. Objetivo: relatar um caso clínico de restauração de um dente posterior com substrato escurecido utilizando uma resina composta Bulk-Fill de média viscosidade associada a um agente opacificador. Relato do caso: após exame clínico e radiográfico, um paciente do sexo masculino com 50 anos de idade foi informado sobre a necessidade de substituição de uma restauração de amálgama de prata insatisfatória na superfície oclusal do dente 16. A restauração foi removida e, em seguida, foi realizada a técnica adesiva para a restauração da cavidade utilizando-se um sistema adesivo autocondicionante de dois passos clínicos (AdheSE, Ivoclar Vivadent, Schann, Liechtenstein). Devido ao substrato dentinário escurecido, foi aplicado no fundo da cavidade um agente opacificador (IPS Empress Direct Opaque, Ivoclar Vivadent, Schann, Liechtenstein) e este, então, fotoativado por 40 s. A restauração foi executada com uma resina composta Bulk-Fill (Tetric N-Ceram Bulk-Fill IVB, Ivoclar Vivadent, Schann, Liechtenstein) em incremento único que foi fotoativado por 40 s. Acabamento e polimento foram realizados com auxílio de borrachas abrasivas. Resultado: ao final, obteve-se, com o auxílio do agente opacificador, uma restauração esteticamente satisfatória. Conclusão: é possível executar restaurações de maneira mais rápida com resina composta Bulk-Fill de média viscosidade. Entretanto, por se tratar de um material essencialmente translúcido, é recomendado o uso de um agente opacificador em dentes com substrato escurecido a fim de se obter um resultado esteticamente satisfatório.