The influence of filler load in 3D printing resin-based composites.

OBJECTIVE: To evaluate the influence of the barium glass (BG) filler in 3D printing resin-based composites for restorative structures. METHODS: Experimental 3D printing resin-based composites were formulated with UDMA 70%wt, Bis-EMA 20%wt, and TEGDMA 10%wt. Photoinitiators TPO and DFI (2%wt) were used. BG was incorporated at 40%wt and 50%wt. 0%wt BG was used as negative control and the VarseoSmile Crownplus (Bego) was used as a commercial control. Specimens were printed using a 3D printer. Subsequently, specimens were washed and submitted to post-curing with 405 nm at 60ºC for 2 × 20 min at FormCure (FormLabs). 3D printing resin-based composites were evaluated by flexural strength, degree of conversion, softening in solvent, radiopacity, and cytotoxicity against gingival fibroblasts. Data were statistically analyzed using one-way ANOVA (α = 0.05). RESULTS: No significant differences in flexural strength were showed between BG40% (90.5 ± 5,4 MPa), BG50% (102.0 ± 11.7 MPa) and VA (105.2 ± 11.7 MPa). Addition of 40% and 50% of BG showed no influence in the degree of conversion compared to VA (p > 0.05). All groups showed softening in solvent after immersion in ethanol (p < 0.05). All groups showed more than 1mmAl of radiopacity. BG50% showed significantly higher radiopacity (2.8 ± 0.3 mmAl) than other groups (p < 0,05). Cytotoxicity evaluation showed gingival cell viability higher than 80% for all groups. SIGNIFICANCE: Addition of up to 50%wt of barium glass in experimental 3D printing resin-based composites showed promising results for long-term restorative structures.

The effect of tooth bleaching using violet LED (405-410 nm) on the properties of resin-based composites.

BACKGROUND: The objective of this study was to evaluate the effect of bleaching techniques, including or not the use of violet light (405-410 nm), on resin-based composites' color, surface roughness, nanohardness, and elastic modulus. METHODS: Ninety-six disk-shaped specimens (12 mm x 2 mm; n = 12) were prepared using Filtek Z350 XT (Z350) and IPS Empress Direct (ED) resin-based composites. After 24 h, specimens were stained in red wine for 28 days. After staining, specimens were divided into four experimental groups: 40 % Hydrogen Peroxide (HP); Violet Light (VL); 40 % Hydrogen Peroxide associated with Violet Light (HP+VL), and a control group - no treatment (NT). Specimens were evaluated at six experimental times: initial (24 h after light curing); after staining and after the 1st, 2nd, 3rd, and 4th bleaching sessions regarding the color change (ΔE00, L*, a*, b*, and WID); roughness (Ra), nanohardness and elastic modulus (GPa). Two-way analysis of variance for repeated measures was performed (α=0.05 %). RESULTS: There was a statistically significant difference between staining and the 1st bleaching session for all ED groups (p<0.05). After the last bleaching session, there were no differences between the experimental and the control groups of both resin-based composites. Bleaching using violet light did not change the roughness, nanohardness and elastic modulus of the tested resin-based composites (p>0.05). CONCLUSIONS: Although hydrogen peroxide and violet light remove pigments from resin-based composites without affecting their surface roughness, nanohardness, and elastic modulus, the color change was similar to the one obtained by immersion in distilled water.

Comparison between a bulk-fill resin-based composite and three luting materials on the cementation of fiberglass-reinforced posts.

Objectives: This study verified the possibility of cementing fiberglass-reinforced posts using a flowable bulk-fill composite (BF), comparing its push-out bond strength and microhardness with these properties of 3 luting materials. Materials and Methods: Sixty endodontically treated bovine roots were used. Posts were cemented using conventional dual-cured cement (CC); self-adhesive cement (SA); dual-cured composite (RC); and BF. Push-out bond strength (n = 10) and microhardness (n = 5) tests were performed after 1 week and 4 months of storage. Two-way repeated measures analysis of variance (ANOVA), 1-way ANOVA, t-test, and Tukey post-hoc tests were applied for the push-out bond strength and microhardness results; and Pearson correlation test was applied to verify the correlation between push-out bond strength and microhardness results (α = 0.05). Results: BF presented higher push-out bond strength than CC and SA in the cervical third before aging (p < 0.01). No differences were found between push-out bond strength before and after aging for all the luting materials (p = 0.84). Regarding hardness, only SA presented higher values measured before than after aging (p < 0.01). RC and BF did not present 80% of the maximum hardness at the apical regions. A strong positive correlation was found between the luting materials' push-out bond strength and microhardness (p < 0.01, R2 = 0.7912). Conclusions: The BF presented comparable or higher push-out bond strength and microhardness than the luting materials, which indicates that it could be used for cementing resin posts in situations where adequate light curing is possible.

Contemporary flowable bulk-fill resin-based composites: a systematic review.

Flowable bulk-fill resin-based composites (BF-RBCs) represent a new and interesting alternative for the bulk-fill restorative techniques in the posterior region. However, they comprise a heterogeneous group of materials, with important differences in composition and design. Therefore, the aim of the present systematic review was to compare the main properties of flowable BF-RBCs, including their composition, degree of monomer conversion (DC), polymerization shrinkage and shrinkage stress, as well as flexural strength. The search was conducted following PRISMA guidelines in the Medline (PubMed), Scopus and Web of Science databases. In vitro articles reporting on the DC, polymerization shrinkage/shrinkage stress, and flexural strength of flowable BF-RBCs strength were included. The QUIN risk-of-bias (RoB) tool was used for assessing the study quality. From initially 684 found articles, 53 were included. Values for DC ranged between 19.41 and 93.71%, whereas polymerization shrinkage varied between 1.26 and 10.45%. Polymerization shrinkage stresses reported by most studies ranged between 2 and 3 MPa. Flexural strength was above 80 MPa for most materials. A moderate RoB was observed in most studies. Flowable BF-RBCs meet the requirements to be indicated for bulk fill restoration technique in the posterior region. However, important variations among composition and properties hinder extrapolation of the results to materials different from those reported here. Clinical studies are urgently required to assess their performance under a real working scenario.

In-vitro pulpal temperature increases when photo-curing bulk-fill resin-based composites using laser or light-emitting diode light curing units.

OBJECTIVE: To evaluate the in vitro pulpal temperature rise (ΔT) within the pulp chamber when low- and high-viscosity bulk-fill resin composites are photo-cured using laser or contemporary light curing units (LCUs). MATERIALS AND METHODS: The light output from five LCUs was measured. Non-retentive Class I and V cavities were prepared in one upper molar. Two T-type thermocouples were inserted into the pulp chamber. After the PT values reached 32°C under simulated pulp flow (0.026 mL/min), both cavities were restored with: Filtek One Bulk Fill (3 M), Filtek Bulk Fill Flow (3 M), Tetric PowerFill (Ivoclar Vivadent), or Tetric PowerFlow (Ivoclar Vivadent). The tooth was exposed as follows: Monet Laser (1 and 3 s), PowerCure (3 and 20 s), PinkWave (3 and 20 s), Valo X (5 and 20 s) and SmartLite Pro (20 s). The ΔT data were subjected to one-way ANOVA followed by Scheffe's post hoc test. RESULTS: Monet 1 s (1.9 J) and PinkWave 20 s (30.1 J) delivered the least and the highest amount of energy, respectively. Valo X and PinkWave used for 20 s produced the highest ΔT values (3.4-4.1°C). Monet 1 s, PinkWave 3 s, PowerCure 3 s (except FB-Flow) and Monet 3 s for FB-One and TP-Fill produced the lowest ΔT values (0.9-1.7°C). No significant differences were found among composites. CONCLUSIONS: Short 1- to 3-s exposures produced acceptable temperature rises, regardless of the composite. CLINICAL SIGNIFICANCE: The energy delivered to the tooth by the LCUs affects the temperature rise inside the pulp. The short 1-3 s exposure times used in this study delivered the least amount of energy and produced a lower temperature rise. However, the RBC may not have received sufficient energy to be adequately photo-cured.

Impacto de la luz operatoria sobre las resinas compuestas: evaluación de su contracción / The impact of operative light on composite resins: evaluation of their shrinkage

El objetivo de este estudio fue analizar el comportamiento, contracción volumétrica, de diferentes resinas compuestas de fotopolimerización, expuestas a variadas condiciones de incidencia lumínica. Se tomaron volúmenes estandarizados de 7 resinas compuestas (microhíbridas y nanohíbridas y nanoparticulados) que se colocaron sobre una línea de referencia en portaobjetos, cubriéndose luego con otro y aplicando una fuerza previamente establecida. Se midió luego con un calibre electrónico la variaciones en el diámetro de la muestra bajo tres situaciones diferentes: luz ambiente (natural), luz foco (halógena), luz artificial (tubos fluorescentes) y sus combinaciones. Resultados: Se observó la mayor variación porcentual al exponer a las muestras simultáneamente a la luz ambiente, artificial y operatoria, siendo los valores más altos de reducción para las resinas compuestas Brilliant NG Coltene (Dentina) y Miris 2 Coltene (Dentina) con -2.52% y -2.7% respectivamente. Conclusión: existieron modificaciones en el volumen de todos los materiales expuestos a las diferentes condiciones de luz y tiempo de exposición. Comparando los resultados con el estudio previo (2007) se pude inferir que los materiales usados en el presente estudio resultaron más fotosensibles, dado que a similar exposición, aumentaron y/redujeron su tamaño en mayor medida (AU)

How do the optical properties of the bulk fill posterior composites change after 2 years of simulated toothbrushing? / Como as propriedades ópticas de compósitos bulk fill se comportam após 2 anos de escovação simulada?

Objective: The objective of this study was to evaluate the alteration of the optical properties of bulk fill resin-based composites after two years of simulated toothbrushing. Material and Methods: Three high-viscosity bulk fill resin composites and one conventional sculptable resin composite (control) were analyzed. Five specimens of each resin composite were prepared, and roughness, color, translucency and gloss were evaluated initially and after one and two years of simulated toothbrushing. The specimens were submitted to electric simulated toothbrushing (14600 strokes / 100 g) using a commercially available soft bristle toothbrush and toothpaste slurry in a proportion of 1:2 by weight. The brushing scheme was of 40 cycles per day (2 cycles per second / 280 cycles in a week). The optical properties and the roughness data were analyzed by a multifactor analysis of variance (MANOVA) and a Tukey post hoc test. Results: The baseline and final values of Ra and Sa were submitted to linear regression analyses, all of which were performed at a significance level of 5%. Gloss and roughness presented statistical differences between the resin-time interactions in all composite resins. The gloss (72.5%) and roughness (89.4%) worsened significantly after brushing, but the authors didn't find statistically significant differences when evaluating translucency and color. Conclusion: Based in the results, it could be concluded that the simulated brushing degraded the gloss and roughness of the used high-viscosity bulk fill composites. (AU)

Objetivo: O objetivo deste estudo foi avaliar a alteração das propriedades ópticas de resinas compostas do tipo bulk fill após dois anos de escovação simulada. Material e Métodos: Foram analisadas três resinas compostas do tipo bulk fill de alta viscosidade e uma resina composta convencional (controle). Cinco corpos-deprova de cada resina composta foram preparados e a rugosidade, cor, translucidez e brilho foram avaliados inicialmente e após um e dois anos de escovação simulada. Os espécimes foram submetidos a escovação dental simulada (14.600 golpes / 100 g) utilizando-se escova de dentes de cerdas macias comercialmente disponíveis e uma pasta composta de dentifrício e água na proporção de 1:2 em peso. O esquema de escovação foi de 40 ciclos por dia (2 ciclos por segundo / 280 ciclos por semana). As propriedades ópticas e os dados de rugosidade foram analisados por uma análise de variância multifatorial (MANOVA) e um teste post hoc de Tukey. Resultados: Os valores iniciais e finais de Ra e Sa foram submetidos a análises de regressão linear, todas realizadas ao nível de significância de 5%. O brilho e a rugosidade apresentaram diferenças estatísticas entre as interações resina-tempo em todas as resinas compostas. O brilho (72,5%) e a rugosidade (89,4%) pioraram significativamente após a escovação, mas os autores não encontraram diferenças estatisticamente significativas ao avaliar a translucidez e a cor. Conclusão: Com base nos resultados, pôde-se concluir que a escovação simulada degradou o brilho e a rugosidade das resinas compostas do tipo bulk fill avaliadas. (AU)