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.

Evaluating the effects of different beverages with daily consumption habits on the wear of restorative materials.

The aim of this study was to investigate the cumulative effects of fruit juices and/or alcoholic beverages on wear track area of the restorative materials by simulating the oral environment in vitro. A microhybrid, a sub-microhybrid, a nanofill resin composite, and a giomer material were used. A daily exposure habits model was created to simulate consumption frequency of acidic and/or alcoholic beverages. Two-body wear tests were carried out using a reciprocating wear tester. ANOVA and Tukey's HSD tests were used for statistical analyses (p < 0.05). When considering experimental groups related to daily exposure habits, statistical difference was found between restorative materials in terms of wear track area (p < 0.01). Joint effect of rmaterial and exposure on wear track area was statistically significant (p < 0.01). Giomer was found to be more affected by acidic and alcoholic beverages. Microhybrid resin composites showed less wear than the other restorative materials. Cumulative effects of alcoholic beverages and fruit juice on wear track area of materials could be related to material's composition and frequency of consumption of acid or ethanol-containing beverages. Daily cumulative effect of acidic and alcoholic beverages was found to be stronger than only acidic fruit juice consumption in terms of wear track area. The plasticizing effect and the concentration of ethanol in the alcoholic beverages provided the basis for the increased wear track area on the restorative materials.

Influence of Bleaching Regimen and Time Elapsed on Microtensile Bond Strength of Resin Composite to Enamel.

OBJECTIVES: The aim of this study was to evaluate the effects of time elapsed since bleaching and different bleaching regimens on the microtensile bond strength of resin composite to enamel. METHODOLOGY: Forty flattened buccal enamel surfaces were divided into four groups: An unbleached (control) group and three bleaching groups. Control group specimens were not subjected to a bleaching regimen (Group 1), while those in the bleaching groups were bleached as follows: opalescence 10% (Group 2), whiteness perfect 16% (Group 3), and whiteness hydrogen peroxide 35% (Group 4). Thereafter, the bleached specimens were divided into three subgroups (n = 4 teeth each) for restoration according to predetermined posttreatment time intervals (immediately, 1 week, and 2 weeks). Bonded specimens were then sectioned and subjected to µTBS testing. The data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests at α = 0.05. RESULTS: There was a significant difference in the µTBS of the resin composite to enamel in groups that were bonded immediately after bleaching and in the control group (P < 0.05). Compared to the control group, the µTBS in Groups 2, 3, and 4 decreased significantly 1-week postbleaching (P < 0.05). No significant difference in µTBS was observed between the bleached and unbleached groups 2 weeks after treatment (P > 0.05). CONCLUSIONS: Adhesive restorative procedures could not be performed immediately or after 1 week irrespective of the type or concentration of bleaching system used. Composite restorations on bleached enamel surfaces should be performed after an interval of at least 2 weeks.

Effects of different kinds of beers on the surface roughness of glazed and polished methacrylate and Silorane-based composites: a 1-month study.

BACKGROUND: The aim of this in vitro study was to evaluate the effect of different kind of beers on the surface roughness of glazed and polished methacrylate- and Silorane-based resin composites after different immersion periods. METHODS: Methacrylate-based resin composites (Tetric N-Ceram, Ceram-X) and a Silorane-based resin composite (Filtek Silorane) were tested in the study. A total of 126 specimens (n=42 for each composite) were fabricated using a cylindrical custom metal mould. Surface roughness measurement was performed using a profilometer at baseline and after a 1-week and 1-month immersion in different kind of beers or distilled water. The results were analysed using repeated measure ANOVA and Tukey's HSD test (α=0.05). RESULTS: Repeated measure ANOVA results revealed that immersion period was a significant factor in the surface roughness of the tested specimens (p<0.001). The lowest surface roughness values were obtained with the specimens' polished Optidisc+BisCover LV. Regardless of the polishing systems used, Tetric N-Ceram showed the statistically lowest surface roughness values (p<0.05), whereas Filtek Silorane showed the highest surface roughness (p<0.001). CONCLUSION: The surface roughness values of the tested resin composites were affected by the polishing procedure used, the exposure time in the solutions and the type of composite resin.

Prevalence of dental injuries and awareness regarding mouthguards among basketball players and coaches.

BACKGROUND: Dental injuries are frequently occurred by an impact to facial area among basketball players. In fact, mouthguards are able to absorb the power of impacts and protect teeth from excessive forces, it is crucial for players even at training to wear mouthguards. To determine the prevalence of dental injuries and investigate the awareness about the use of mouthguards among basketball players and coaches. METHODS: A 14-item questionnaire was designed and tested among licensed basketball players and coaches, all of whom were continuously exposed to the risk of dental injuries. The questions focused on the prevalence of dental injuries and attitudes and knowledge regarding the use of mouthguards among the players and coaches. Data were calculated using descriptive statistics and χ2 tests. RESULTS: A total of 53 coaches (18-69 years) and 351 players (12-38 years) participated. Of these, 124 players (35% of the total sample) had experienced oral injuries, including soft tissue lacerations (80.6%), fractures (17.7%) and avulsions (1.6%). Although the players had sustained dental injuries, 95% of them found mouthguards to be protective, and only 6.3% (N.=22) actually used a mouthguard. The rate of mouthguard use among players who had experienced an oral injury was significantly higher than that among players without any history of injury (P<0.05). Although 98% of the coaches believed that mouthguards could prevent dental injuries, only 47% of them suggested their use to their players. The most common reasons for not using a mouthguard were discomfort (37.7%) and difficulty in breathing (7.3%) or talking (6.4%). CONCLUSIONS: This study showed that the use of mouthguards among basketball players is very rare, with inadequate knowledge among the coaches. Consequently, more information is required through sports associations and dentists.

Color Stability of Composites After Short-term Oral Simulation: An in vitro Study.

BACKGROUND: Although most of the studies investigated color stability of different restorative materials, evaluation of color stability of composites after immersion in multiple beverages in the same day by an in vitro oral simulation study is unclear. OBJECTIVE: To assess color change of different restorative materials at the end of days 1, 14, and 30 of immersion in multiple liquid types to mimic the oral environment in vitro. METHOD: Ten disc-shaped specimens were made from each of four different resin composites (Filtek Z250, Voco x-tra base, Beautifil Flow Plus, Beautifil II). Baseline color value of each sample was measured using a spectrophotometer. Each composite was respectively immersed in coffee, an orange/pomegranate juice mixture, black tea, and a mouth rinse on the same day to mimic daily liquid consumption of individuals. Color measurements were taken after 1, 14, and 30 days by spectrophotometer and color change values were calculated. Statistical analyses were executed by one-way ANOVA/Tukey HSD and repeated-measures ANOVA. RESULTS: All materials showed significant color change after 1, 14, and 30 days (P < 0.01) of immersion in liquids, with the lowest color alteration observed at the 1st day and the highest observed after the 30th day. Among the materials tested, at each time point (1, 14, and 30 days), the lowest color alteration was detected in Filtek Z250 and the highest color alteration was detected in Beautifil II. CONCLUSION: Color alteration of composite resins is affected by composite type and storage time. With the exception of 1 day of storage, color changes of all materials were substantial and clinically unacceptable.

The effect of a modeling resin and thermocycling on the surface hardness, roughness, and color of different resin composites.

STATEMENT OF PROBLEM: The application of modeling resin could affect the surface quality and color of resin composites. PURPOSE: To evaluate the effects of modeling resin on the microhardness, roughness, and color of composite restorations, with and without thermocycling. METHODS: Sixty disc-shaped specimens for each resin composite were prepared in three groups: Group 1: A resin composite disc was cured against a polyester matrix and finished/polished; Group 2: A composite instrument was wetted with Bisco Modeling Resin (Bisco, Schaumburg, IL, USA) to smooth the composite surface, which was cured against a polyester matrix and finished/polished; Group 3: A composite instrument was wetted with modeling resin to smooth the composite surface, which was cured against a polyester matrix. Microhardness, roughness, and color were measured 24 hours after curing and after 10,000 thermocycles. RESULTS: Modeling resin significantly influenced the microhardness of GrandioSO (Voco, Cuxhaven, Germany) and Gradia Direct Posterior (GC America, Alsip, IL, USA), and the surface roughness of GrandioSO, Filtek Silorane (3M ESPE, St Paul, MN, USA), and Aelite All Purpose Body (Bisco) (p < 0.05). The microhardness of the Group 1 resin composites was affected by thermocycling (p < 0.05); however, thermocycling had no significant effect on surface roughness (p > 0.05). Tested composites showed clinically perceptible color changes after thermocycling. In Group 1, Filtek Ultimate (3M ESPE) showed the lowest color change (p < 0.05), and in Group 2, Filtek Silorane showed the highest significant color changes (p < 0.05). CONCLUSIONS: Modeling resin did not affect the microhardness, surface roughness, and color of Aelite LS Posterior (Bisco), Filtek Ultimate (3M ESPE), and Clearfil Majesty Esthetic (Kuraray Medical Inc, Tokyo, Japan) specimens. Also, thermocycling process only affected microhardness of tested resin composites. CLINICAL SIGNIFICANCE: The effect of modeling resin on surface microhardness, roughness, and color stability of composite materials depends on the type of resin composite. In clinical practice, the adverse effects of modeling resin might be alleviated by a proper finishing and polishing procedure.

The effects of glass ionomer and flowable composite liners on the fracture resistance of open-sandwich class II restorations.

This in vitro study aimed to investigate the effects of glass-ionomer and flowable composite liners on the fracture resistance of Class II amalgam and composite restorations. Group 1 cavities were restored with amalgam and Group 4 cavities with nanofill composite after the application of a dentin-bonding agent. For the remaining groups, light-cured-glass-ionomer liner was used in a gingival floor proximal box (Groups 2, 5) or flowable composite was used as a liner (Groups 3, 6), the remainder of the cavity was restored with amalgam (Groups 2, 3) or composite (Groups 5, 6). The restorations were loaded in compression to failure. The data was analyzed using Tukey's multiple comparison test. The fracture resistance was significantly higher (p<0.05) in Group 3 than in all other groups, except Group 2 (p>0.05). Flowable composite, glass-ionomer liners increased the fracture resistance of open-sandwich Class II amalgam restorations.