Effects of polishing procedures on optical parameters and surface roughness of composite resins with different viscosities.

The aims of this study were to evaluate the optical properties of flowable and injectable composites after polishing, such as translucency (translucency parameter [TP], TP00), opalescence (OP-BW), chroma (C*ab), refractive index (RI), and change in surface roughness (Ra, Rz). Ninety disc-shaped samples were prepared from micro-hybrid, flowable, and injectable composites and divided into 3 groups according to the polishing systems (n=10). The RI was measured with an Abbe refractometer, and optical measurements were performed with a spectrophotometer. The surface roughness was measured with a two-dimensional profilometer. Data were analyzed with the generalized linear model method and two-way analysis of variance. The results showed that the polishing procedure did not significantly impact the RI (p=0.987). Injectable composite had the highest translucency (TP=28.67; TP00=13.49) and opalescence (OP-BW=13.11); showed the lowest C*ab value (17.95). Also, the effects of the composite type and polishing procedure on surface roughness were statistically significant (p=0.047 and p<0.001).

Evaluation the Effect of Different Antioxidants Applied After Bleaching on Teeth Color Stability / Avaliação do efeito de diferentes antioxidantes aplicados após o clareamento na estabilidade da cor dos dentes

Objective: Vital bleaching is a popular treatment option for discolored teeth; but at post-treatment stage, loss of adhesion is highly reported. Literature focused on antioxidant application for the answer of this issue. The aim of this study was to compare the effects of six different antioxidants on color stability of bleached teeth. Material and Methods: This study included total of 84 extracted intact non-carious lower incisors. 35% hydrogen peroxide was applied on the labial surfaces of specimens in accordance with manufacturer's instructions. The bleached teeth were divided into 7 groups. No antioxidants were applied to the control group. For the experimental groups, the following antioxidants were applied for 10 minutes each: 5% proanthocyanidin, 5% sodium ascorbate, 5% lycopene, %5 green tea, %5 white tea and %5 α-tocopherol. CIE L*, a* and b* values of the teeth were measured by a spectrophotometer. One-way ANOVA was used to determine the differences among the groups. Multiple comparisons were examined with Tukey HSD. Results: The one-way ANOVA test revealed a statistically significant difference between the groups (p < 0.005). Highest color change was observed in lycopene group and the lowest in green tea group. Conclusion: Proanthocyanidin, white tea and green tea could be considered as post-bleaching antioxidant alternatives based on their herbal nature. (AU)

Objetivo: O clareamento vital é uma opção popular de tratamento para dentes descoloridos, mas na fase pós-tratamento, a perda de adesão é altamente relatada. A literatura enfocou a aplicação de antioxidantes para a resposta desta questão. O objetivo deste estudo foi comparar os efeitos de seis diferentes antioxidantes na estabilidade da cor de dentes clareados. Material e Métodos: Este estudo incluiu um total de 84 incisivos inferiores extraídos, intactos e não cariados. Peróxido de hidrogênio a 35% foi aplicado nas superfícies labiais dos espécimes de acordo com as instruções do fabricante. Os dentes clareados foram divididos em 7 grupos. Nenhum antioxidante foi aplicado ao grupo controle. Para os grupos experimentais, os seguintes antioxidantes foram aplicados por 10 minutos cada: proantocianidina a 5%, ascorbato de sódio a 5%, licopeno a 5%, chá verde a 5%, chá branco a 5% e α-tocoferol a 5%. Os valores CIE L *, a * e b * dos dentes foram medidos por um espectrofotômetro. ANOVA um fator foi usada para determinar as diferenças entre os grupos. As comparações múltiplas foram examinadas com Tukey HSD. Resultados: O teste ANOVA revelou uma diferença estatisticamente significativa entre os grupos (p <0,005). A maior mudança de cor foi observada no grupo do licopeno e a menor no grupo do chá verde. Conclusão: Proantocianidina, chá branco e chá verde podem ser considerados como alternativas antioxidantes pós-clareamento com base em sua natureza fitoterápica. (AU)

Comparison of the Shear Bond Strength of Metal Orthodontic Brackets Bonded to Long-term Water-aged and Fresh Porcelain and Composite Surfaces.

OBJECTIVE: The aim of the present study was to compare the shear bond strength (SBS) of metal orthodontic brackets bonded to long-term water-aged and fresh porcelain and composite surfaces. METHODS: One porcelain (Vitadur Alpha (VA)) and three composite (Filtek Ultimate (FU), Tetric EvoCeram (TEC), and Gradia Direct Anterior (GDA)) materials were evaluated in the present study. First, 10 discs from each material were prepared and subjected to the aging procedure for 5 years. Then, for comparison, another 10 discs from each material were prepared as fresh surfaces and stored in distilled water for 24 h. Metal brackets were bonded to the prepared disc surfaces, and after being stored in water for 24 h, they were subjected to shear bond test using a universal testing machine. Adhesive remnant index (ARI) scores were obtained by examining the disc surfaces under a stereomicroscope at 10× magnification. Kruskal-Wallis test was used to compare the aged and fresh groups. RESULTS: Although the difference between the SBS between the aged and fresh groups with VA, FU, and TEC was not significant, the SBS was significantly higher in the fresh group with GDA. With regard to ARI scores, there was no significant difference between the aged and fresh groups with FU and GDA, whereas the ARI scores of the aged groups with VA and TEC were higher. CONCLUSION: It was concluded that the aged restoration materials have a distinctive influence on the SBS of metal orthodontic brackets.

The effects of sintering temperature and duration on the flexural strength and grain size of zirconia.

Objective: This study investigated the effect of different sintering temperatures and times on the flexural strength and grain size of zirconia. Material and methods: Zirconia specimens (In-Coris ZI, In-Coris TZI, 120 samples) were prepared in a partially sintered state. Subsequently, the specimens were randomly divided into three groups and sintered at different final sintering temperatures and for various durations: 1510 °C for 120 min, 1540 °C for 25 min and 1580 °C for 10 min. Three-point flexural strength (for 120 samples, 20 samples per group) was measured according to the ISO 6872: 2008 standards. The grain sizes were imaged by scanning electron microscopy (SEM) and the phase transitions were determined by X-ray diffraction (XRD). The data were analyzed using one-way ANOVA and Duncan tests (p < 0.05). Results: The highest flexural strength was observed in ZI and TZI samples sintered at 1580 °C for 10 min. The differences between the ZI samples sintered at 1510 °C for 120 min and those sintered at 1540 °C for 25 min were statistically insignificant. Also, TZI samples sintered at 1510 °C for 120 min and those sintered at 1540 °C for 25 min also did not show any statistically significant differences. There were no visible differences in the grain sizes between the ZI and TZI specimens. The XRD patterns indicated similar crystalline structure for both materials subjected to the three different procedures. Conclusions: The results of this study showed that experimented high sintering temperature and short sintering time combination increases the flexural strength of zirconia.