Effects of different remineralizing agents on color stability and surface characteristics of the teeth following vital bleaching

The aim of the study was to investigate the effects of various remineralizing agents on the color stability and surface characteristics of the teeth after vital bleaching. The extracted 96 human incisors were used for the study. Initially, the samples were randomly divided into two groups and exposed to in-office and at-home bleaching agents. Then, the groups were divided into six subgroups (n = 8), including the control group did not undergo remineralization after bleaching, according to five remineralizing agents (Gelato APF Gel, Remin Pro, Tooth Mousse, MI Paste Plus, Curodont Protect). Surface roughness was assessed at baseline, after bleaching and remineralization procedures. Color measurements of the samples were obtained at baseline, after bleaching and then after immersion in the staining solution following remineralization process. Scanning electron microscopy and atomic force microscopy (AFM) analyzes were carried out in order to examine the morphological changes on the surface of the enamel. The independent t-test, paired-samples t-test, and one-way ANOVA was used to compare the data and post-hoc LSD test to compare the difference among the study groups (alpha = .05). Surface roughness increased following in-office and at-home bleaching in all groups, and reduced after application of remineralizing agents in all groups. Significant differences were found among the groups with respect to changes in surface roughness and color values following treatment with remineralizing agents (p <.05). AFM analyses revealed increased surface roughness after bleaching and a reduction of rough surfaces following treatment with remineralizing agents. Remineralizing agents can be used to reduce postbleaching increase in surface roughness and to maintain color stability after bleaching

Effect of different polishing systems on the surface roughness of various bulk-fill and nano-filled resin-based composites: An atomic force microscopy and scanning electron microscopy study

The aim of the study was to evaluate the effects of different polishing systems on the surface roughness of various bulk-fill and nano-filled resin-based composites using different methods. For the study, a total of 192 disc-shaped samples (10-mm wide and 2-mm thick) were prepared from four different bulk-fill composites (Filtek Bulk Fill, X-tra fil, Beautifil-Bulk Restorative and Fill Up) and two nano-filled resin-based composites (Ceram.x SphereTEC and Filtek Z550). The samples in each composite group were divided into four subgroups according to the polishing system to be used (n = 8). Four different polishing systems (Sof-Lex Diamond, Clearfil Twist Dia, HiLuster Plus, OptiDisc) were applied. Then, surface roughness measurements were carried out using a contact-type profilometer. One sample from each group was subjected to atomic force microscopy (AFM) and scanning electron microscope (SEM) examinations. Surface roughness (Ra) values were statistically analyzed in terms of composites and polishing systems using the two-way analysis of variance (ANOVA) and comparisons among groups were performed using the Tukey test (alpha = .05). Surface roughness values differed significantly in relation to the composite and polishing system used (p < .05). Among all composites, the lowest surface roughness values were obtained in the groups treated with the OptiDisc polishing system (except Beautifil-Bulk Restorative), whereas the highest roughness values were observed in the group polished with Clearfil Twist Dia (except Filtek Z550). X-tra fil showed the highest roughness value with all polishing systems tested. The findings of AFM analyses were consistent with profilometric measurements. The nano-filled resin-based composites showed smoother surface than bulk-fill composites and the type of the polishing systems was found to affect surface roughness

Effect of Light Sources on Bond Strength of Different Composite Resins Repaired with Bulk-Fill Composite

The aim of this study was to evaluate and compare the effects of different light sources on shear bond strength when bulk-fill composite was used for the repair of different composite resins. A total of 126 samples made from six resin composites with different properties were aged (thermal-cycling with 5000 cycle), exposed to the same surface treatments and adhesive procedure. Then, they were repaired with a bulk-fill composite. At the polymerization step, each group was divided into three subgroups (n=7) and light cured with a QTH light source for 40s and two different LED light sources for 20s. Subsequently, the specimens were aged in distilled water at 37 degrees C for 4 weeks and then subjected to shear bond strength test. Then, the specimens were examined under a stereomicroscope to identify modes of failure and visualized by Scanning Electron Microscope. Data obtained from the study were analyzed using ANOVA and Tukey HSD Test (alpha=0.05). In all groups, the light curing units had an impact on shear bond strength (p<0.05). Among the study groups, the greatest bond strength values were observed in the specimens repaired using the LED and the specimens repaired with the QTH light curing unit had the lowest bond strength values. It was concluded that the content of composite resins and light curing units may influence bond strength of different composites repaired with the bulk-fill composite

Analysis of Monomer Elution from Bulk-fill and Nanocomposites Cured with Different Light Curing Units Using High Performance Liquid Chromatography

The aim of this study was to investigate the effect of different light curing units and light modes on the amount of residual monomers eluted from different resin-based composites. Initially, a total of 96 composite samples (N=24/group) were prepared from 3 bulk-fill composites with different characteristics and a nanohybrid composite using a mold (diameter: 5 mm, height: 4 mm). Then, each group was divided into 4 subgroups (n=6). Polymerization of the resin composites was performed using a halogen light source (Hilux 250), a 2nd generation LED device (Elipar DeepCure -S) and a 3rd generation LED device (Valo, standard and ultra modes). Samples were stored in 75% ethanol solution and residual monomers eluted in the solution were analyzed with HPLC after 1 day and 1 month. Monomer concentrations corresponding to the peak areas in chromatograms were calculated in ppm to obtain data for statistical analysis. The study data were analyzed using One Way ANOVA (p=0.05) and post-hoc Tukey tests. The type of the light-curing unit significantly affected the amount of residual monomer released in all composite groups (p<0.05). Except the Fill-Up composite groups, the least monomer elution was detected in the groups cured with Elipar DeepCure-S. Residual monomer amounts detected after 30 days were significantly increased in comparison to those eluted after 1 day in all groups. In light of these findings, it was concluded that the light curing units might have an impact on the monomer elution from different composites

Effect of layer thickness on residual monomer release in polymerization of bulk-fill composites

The aim of the present study was to investigate and compare the quantity of residual monomers leached from the bulk-fill composites with different compositions polymerized at varying layer thickness. Three bulk-fill (X-tra-fil, Beautifil Bulk Restorative, Fill-Up) and a nanohybrid composite (Filtek Z550) were used for the study. The composite resin samples were prepared with a stainless steel mold. For each composite, two groups were constructed. The samples in the first group were prepared using the 2 + 2 mm layering technique. In the second group, the composite samples were applied as a 4 mm-thick one layer and polymerized. Then, each composite samples were kept in a 75% ethanol solution and residual monomers released from composite resins were analyzed with an HPLC device after 24hour and I month. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests. Except the Fill-Up, all of residual monomer elution from the bulk-fill composites was significantly affected by the layer thickness (p < 0.05). The greatest monomer release was detected at I month after polymerization as a single 4 mm layer for Beautifil Bulk Restorative. Fill-Up composite showed similar residual monomer release in polymerization at different layer thicknesses compared to other composite resins. In the 2 + 2 mm layering technique, the least monomer elution was detected in the Filtek Z550 composite group. While BisGMA was the most released monomer in X-tra fil composite, UDMA was the most released monomer in all other composite resins. During polymerization of the bulk-fill composite, the layer thickness of the composite applied may affect the amount of residual monomers released from the composite resins. Conventional composites may release less monomer than bulk-fill composites when used with layering