Background and aims:Bleaching might affect structural properties of composite materials, and lead to monomer release. This study aimed to evaluate the effect of Laser-assisted and conventional in-office bleaching on the release of BIS-GMA, TEGDMA, and UDMA monomers from a nanohybrid and a microhybrid BIS-GMA based composite. Materials and Methods: 32 samples of each composite, were divided into 4 subgroups; subgroup 1: Conventional in-office bleaching (CIB) with the Opalescence Boost PF 38% gel, subgroup 2: Laser-assisted bleaching (LBO) with the Opalescence Boost PF 38% gel, subgroup 3: Laser-assisted bleaching (LBH) with the JW Power bleaching gel, subgroup 4: (CO) control without bleaching. All the samples were immersed in tubes of 2cc Ethanol 75% medium. The released monomers were analyzed using the high performance liquid chromatography (HPLC) method 24 h, 7, and 28 days. Data's were analyzed by Univariate Analysis of Variance test followed by Tukeys HSD. Results: The amount of TEGDMA monomer released was not significant. However, nanohybrid composites showed significantly more monomer release than microhybrid composites (P < 0.05). For UDMA the interaction was significant only after 1 week. In microhybrid composites, the CO subgroup showed more monomer release than LBH and LBO. In nanohybrid composites, LBH showed more monomer release than CIB and CO subgroups. For BIS-GMA monomers the interaction was significant at all time periods and the LBH subgroup of nanohybrid composite had significantly more BIS_GMA release in comparison to other subgroups. Conclusion: Bleaching by laser with JW Power Bleaching gel led to more monomer release in nanohybrid composite.

This study investigated the effect of different cavity lining techniques on the marginal sealing of Class II composite restorations. A total of 36 human molar teeth, free of caries and fillings, were each prepared with two proximal Class II boxes mesially and distally. In mesial boxes, cavity liners were applied as follows: in group 1, separately cured flowable composite; in group 2, co-cured flowable composite; and in group 3, resin-modified glass ionomer (RMGI). The remaining cavities were filled incrementally with a universal restorative composite. The distal boxes were filled with no liner as controls. After thermocycling, the specimens were immersed in a silver nitrate solution and the microleakage was evaluated. Analysis of variance showed that the degree of microleakage for group 3 was significantly lower than that of the other groups. Based on the results, it was concluded that the use of RMGI as a cavity liner under composite restorations showed the least microleakage. Flowable composites, whether co-cured or separately cured, had no influence on the marginal sealing.

No abstract

Background. Resin composites have various applications. At the same time, they have some drawbacks, such as polymerization shrinkage. Conventional composites are polymerized in 2-mm thick layers. However, in posterior restoration, the 2-mm depth of cure is not satisfactory. To find a solution, resin composites have been vastly improved in terms of fillers, matrix and initiators.Objectives. To evaluate polymerization properties and physical characteristics of fiber-reinforced composites and compare them with bulk-fill composites that are designed for large posterior restorations. Materials and methods.Samples were prepared from each resin composite. The 3-point bending test was performed to evaluate the flexural strength of all composites. The depth of cure of the composite from 1 mm to 4 mm of depth was analyzed using Vickers hardness test (VHN). To analyze the degree of conversion, Fourier-transform infrared spectroscopy (FTIR) of the top and bottom surfaces of the samples with 4-mm thickness was calculated. The data were analyzed using one-way analysis of variance (ANOVA) test followed by post hoc test (95% confidence interval (95% CI)).Results. The Filtek showed the highest flexural strength followed by everX and X-tra fil. At 1-mm depth, X-tra fil had the highest and Gradia had the lowest microhardness. At the 4-mm depth, the microhardness trend was as follows: everX > Filtek > X-tra fil > Gradia > Beautifil. The everX composite had the lowest reduction of the degree of conversion at 4-mm thickness, which showed a significant difference in comparison with Filtek, Gradia and X-tra fil composites. Conclusions.Based on the results of our study, it can be concluded that the fiber-reinforced composite everX showed more favorable results regarding polymerization properties, such as the degree of conversion and the depth of cure. However, the flexural strength results in Filtek were better than those in everX.

Background and Aim: The proportion of smile is a useful tool for creating geometric smiles which are a critical aspect in esthetic dentistry. The aim of this study was to determine the effect of lip line position on acceptable Recurring Esthetic Dental (RED) proportion among lay people. Materials and Methods: A photograph of pose smile of a young female was taken. The position of the lip was changed by Adobe Photoshop CS6 software within three positions (low, medium, and high). Then, we created three RED proportions (54%, 62%, and 70%) for each lip line position. The photographs were ranked from most to least attractive (one to nine) by 40 lay people (20 females and 20 males) with a mean age of 19.4 years. Data were collected and analyzed using Friedman test. Pairwise comparisons were made using Bonferroni correction. The impact of gender on the ratings was evaluated using repeated measures analysis of variance (ANOVA). Results: In the medium lip line group, all three proportions had approximately the same preference rates. The 54% proportion was the least attractive one in the high lip line group (mean=6.819), and the 70% proportion was the least attractive one in the low lip line group (mean=6.881). Conclusion: The acceptable RED proportion cannot be evaluated without consideration of other factors such as lip line position. Esthetics is the result of a harmonious balance between different elements.