Effect of Light Curing Modes on the Color Stability of a Nanohybrid Composite Immersed in Different Beverages / Efecto de diferentes modos de fotopolimerización en la estabilidad del color de una resina compuesta nanohíbrida inmersa en diferentes bebidas

Abstract: Aim: Sufficient polymerization remains as crucial for composites to prevent discoloration. Both LEDs and halogen units are used for polymerization and different curing modes are improved to overcome inadequate polymerization. This in vitro study investigated staining susceptibility of a nano-hybrid resin composite light-cured in different modes and immersed in different staining media. Methods: Disc-shaped specimens were prepared from nano-hybrid resin composite (Filtek Z550) and light- cured according to following modes: Halojen (GI), LED standard (GII), LED pulse (GIII) or LED ramp (GIV). Half of the specimens of each group (n=7) were stored in one of the staining media (red wine or coffee) for 10 min/day during experimental period. Measurements were performed using spectrophotometer according to CIEL*a*b system at baseline and on 7, 28 and 56 days. Colour differences (∆E) between groups were submitted to statistical analysis. Results: Regarding 7-day evaluation, colour change values of specimens immersed in coffee revealed no remarkable difference among curing modes (p>0.05); whereas specimens in GIV were significantly less stained compared to specimens in GII and GIII when immersed in red wine. Regarding 56- days of evaluation, specimens of GIV showed statistically significant colour change in red wine compared to other groups. However specimens in GI revealed the least staining after 56-days of coffee immersion, and this result was statistically different from LED groups. Conclusion: This study suggest that light-curing mode influences the staining susceptibility of the tested composite. Composites polymerized with halogen unit showed lower staining than all LED modes. Despite novel light sources, halogen units may still used reliably at clinics.

Resumen: Objetivo: La polimerización suficiente sigue siendo crucial para que los compuestos eviten la decoloración. Tanto los LED como las unidades halógenas se utilizan para la polimerización y se mejoran los diferentes modos de curado para superar la polimerización inadecuada. Este estudio in vitro investigó la susceptibilidad a la tinción de un compuesto de resina nano-híbrida curado a la luz en diferentes modos y se sumergió en diferentes medios de tinción. Métodos: Las muestras en forma de disco se prepararon a partir de un compuesto de resina nano-híbrida (Filtek Z550) y se curaron con luz de acuerdo con los siguientes modos: Halojen (GI), estándar de LED (GII), pulso de LED (GIII) o rampa de LED (GIV). La mitad de las muestras de cada grupo (n = 7) se almacenaron en uno de los medios de tinción (vino tinto o café) durante 10 minutos / día durante el período experimental. Las mediciones se realizaron utilizando un espectrofotómetro de acuerdo con el sistema CIEL * a * b en la línea de base y en 7, 28 y 56 días. Las diferencias de color (∆E) entre los grupos se sometieron a análisis estadístico. Resultados: Con respecto a la evaluación de 7 días, los valores de cambio de color de las muestras sumergidas en café no revelaron diferencias notables entre los modos de curado (p> 0.05); mientras que las muestras en GIV se tiñeron significativamente menos en comparación con las muestras en GII y GIII cuando se sumergieron en vino tinto. Con respecto a los 56 días de evaluación, las muestras de GIV mostraron un cambio de color estadísticamente significativo en el vino tinto en comparación con otros grupos. Sin embargo, las muestras en GI revelaron la menor tinción después de 56 días de inmersión en el café, y este resultado fue estadísticamente diferente de los grupos LED. Conclusión: este estudio sugiere que el modo de fotopolimerización influye en la susceptibilidad de tinción del material compuesto probado. Los compuestos polimerizados con una unidad halógena mostraron una tinción más baja que todos los modos LED. A pesar de las nuevas fuentes de luz, las unidades halógenas todavía pueden usarse de manera confiable en las clínicas.

Effect of black tea and matrix metalloproteinase inhibitors on eroded dentin in situ.

Purpose of this in situ study was to evaluate the surface properties of eroded dentin specimens activated with three different matrix metalloproteinase (MMP) inhibitors (chlorhexidine [CHX], fluoride, green tea), black tea, and water. One hundred eighty dentin samples were prepared from extracted third molars and then samples divided into six groups. Ten volunteers were carried three specimens of each group, on acrylic palatal appliances, which were fabricated exactly for them (n = 3). Erosive cycles were done by immersing appliances in cup containing Cola and was followed by rinsing with test solutions. Microhardness values were measured. Surface properties were investigated by atomic force microscopy (AFM). Lowest change in microhardness was shown in fluoride group whereas negative control group (water) had the highest change. There were no statistically significant differences among surface roughness changes (p > .05). The least change in microhardness was seen in the fluoride group (13.05 ± 8.07), while the control group showed the highest change (33.80 ± 12.42) and was statistically significant when compared to other groups (p < .05). Besides lowest depth, values were shown in fluoride group as well. AFM evaluations showed macromolecular deposits on surfaces of fluoride, CHX, and black tea groups. No superior results were detected in CHX + fluoride group and black tea showed similar surface characteristics as green tea. Mouthrinses containing not only green tea but also black tea could be beneficial for patients with exposed dentin surfaces. Catechines and theaflavins in teas could be useful for improving surface quality.

An in vitro comparison of different adhesive strategies on the micropush-out bond strength of a glass fiber post

Objectives: To evaluate in vitro the push-out bond strengths of a glass fiber post adhesively luted with self-etchingresin based and self-adhesive luting cements, as well as modified application procedure of self-adhesive lutingcements in combination with single step self-etch adhesives.Materials and methods: Fifty single-rooted human maxillary central incisor teeth were endodontically treated anddivided into five groups (n=10). Glass fiber posts (RelyX Fiber Post) were cemented with the following materials:group 1: ED Primer II/Panavia F 2.0 (PAN); group 2: RelyX Unicem (RU); group 3: Maxcem (MC); group 4:Adper Prompt L-Pop (PLP)/RelyX Unicem; group 5: Optibond all-in-one (OB)/Maxcem. Bonded specimens werecut (1-mm-thick sections) and push-out tests were performed (crosshead-speed, 0.5 mm/min). Data were analyzedby one-way ANOVA followed by the Tukey-HSD test for post hoc comparisons at á = 0.05.Results: The highest bond strength was recorded for groups 4 and 2, with no statistically significant differencesamong them (p>0.05). Group 4 showed significantly higher bond strength than group 1 (p<0.001), group 3(p<0.0001) and group 5 (p<0.0001). Group 1 showed significantly higher bond strength than the group 3 (p<0.05).No statistically significant differences were observed among group 1 and group 2, group 1 and group 5, group 3and group 5. Group 3 showed significantly lower push-out bond strength than the all other luting strategies exceptfor the group 5.Conclusions: The push-out bond strength values of modified application procedure of self-adhesive luting cements(RU and MC) in combination with single step self-etch dentin adhesives (PLP and OB) did not improve the pushoutbond strength of fiber post when compared with those where the conventional use of self-adhesive cements (AU)

An in vitro comparison of different adhesive strategies on the micro push-out bond strength of a glass fiber post.

OBJECTIVES: To evaluate in vitro the push-out bond strengths of a glass fiber post adhesively luted with self-etching resin based and self-adhesive luting cements, as well as modified application procedure of self-adhesive luting cements in combination with single step self-etch adhesives. MATERIALS AND METHODS: Fifty single-rooted human maxillary central incisor teeth were endodontically treated and divided into five groups (n=10). Glass fiber posts (RelyX Fiber Post) were cemented with the following materials: group 1: ED Primer II/Panavia F 2.0 (PAN); group 2: RelyX Unicem (RU); group 3: Maxcem (MC); group 4: Adper Prompt L-Pop (PLP)/RelyX Unicem; group 5: Optibond all-in-one (OB)/Maxcem. Bonded specimens were cut (1-mm-thick sections) and push-out tests were performed (crosshead-speed, 0.5 mm/min). Data were analyzed by one-way ANOVA followed by the Tukey-HSD test for post hoc comparisons at a = 0.05. RESULTS: The highest bond strength was recorded for groups 4 and 2, with no statistically significant differences among them (p >0.05). Group 4 showed significantly higher bond strength than group 1 (p <0.001), group 3 (p <0.0001) and group 5 (p <0.0001). Group 1 showed significantly higher bond strength than the group 3 (p <0.05). No statistically significant differences were observed among group 1 and group 2, group 1 and group 5, group 3 and group 5. Group 3 showed significantly lower push-out bond strength than the all other luting strategies except for the group 5. CONCLUSIONS: The push-out bond strength values of modified application procedure of self-adhesive luting cements (RU and MC) in combination with single step self-etch dentin adhesives (PLP and OB) did not improve the push-out bond strength of fiber post when compared with those where the conventional use of self-adhesive cements.