Effect of thermocycling on the amount of monomer released from bulk fill composite resins

Investigating the Effect of Polyetheretherketone (PEEK) Veneers on Bond Strength and Discoloration When Repairing Various Composites

OBJECTIVES

This study aimed to examine the impact of the strength and color change of composite materials that could be utilized in the repair of polyetheretherketone (PEEK) veneer fractures.

METHODS

The 220 nanoceramic-filled PEEK specimens used in the study were divided into four groups, and color measurements were made on a gray background (n=55): Group N, 1-mm-thick monochromatic composite; Group NN, 2-mm-thick monochromatic composite; Group F, 1-mm-thick 2-mm-diameter short fiber-reinforced composite, placed in the center and polymerized; and Group FF, 2-mm-thick 2-mm-diameter short fiber-reinforced composite, placed in the center and polymerized. The remaining mating surfaces were restored by filling with monochromatic composite and adhesion strength testing by re-measuring the color.

RESULTS

The results of the two-way ANOVA indicated that there was a significant color change caused by both thickness and composite type (p<0.001). Additionally, a significant difference in bond strength was observed between the groups.

CONCLUSION

In PEEK restorations, short fiber-reinforced composites significantly increase bond strength, while the use of monochromatic composites of a certain thickness ensures that color change remains within acceptable limits.

SIGNIFICANCE

 Although PEEK has a superior mechanical structure, it does not meet the aesthetic expectations and needs to be veneered. However, fractures are frequently seen due to low bond strength. Therefore, this study is important because it aims to provide guidance to clinicians on aesthetic and mechanical methods that can be used in PEEK prosthesis repair.

Comparison of degree of conversion performance of bulk-fill resin composites: A systematic review and network meta-analysis of in vitro studies

OBJECTIVES

To systematically compile data on the degree of conversion (DC) for bulk-fill composites using a network meta-analysis.

METHODS

A systematic search for in vitro studies of DC of bulk-fill composites was performed in PubMed, Web of Science, Scopus, and Open Grey. Risk of bias within studies and due to missing evidence was assessed using the Joanna Briggs Institute scoring system and ROB-MEN tool, respectively. The primary outcome was the DC of bulk-fill composites. Surface Under the Cumulative Ranking curve (SUCRA) was used to rank relative performance. Inconsistencies in the model were investigated to ensure its validity and the level of confidence in the network meta-analysis (CINeMA) was assessed.

RESULTS

A total of 28 studies were included in the quantitative analysis. The average DC values (%) for 0-h/top, 0-h/bottom, 24-h/top, and 24-h/bottom were 59.09, 57.14, 66.73, and 63.87, respectively. According to their SUCRA ranking, the best-performing composites were: SonicFill, Venus Bulk Fill, and SDR (0-h/top), Reveal HD, i-Flow Bulk Fill, and Venus Bulk- Fill (0-h/bottom), Venus Bulk Fill, SDR, and QuiXfil (24-h/top), and Venus Bulk Fill, Aura Bulk Fill, and i-Flow Bulk Fill (24-h/bottom). Incoherence between direct and indirect evidence was identified as the most significant factor affecting confidence.

CONCLUSIONS

DC values of bulk-fill composites were within the range commonly reported for previous generations of "conventional" composites, with flowable composites tending to perform better than sculptable composites. High variability in DC data was observed, which may be attributed to incompletely understood methodological differences.

CLINICAL SIGNIFICANCE

DC is a fundamental parameter that influences multiple mechanical and biological properties of resin composites and is particularly relevant for the group of bulk-fill composites that are designed for use in thick layers.

Surface treatments on repair bond strength of aged resin composites

Aims:

The aim was to evaluate the effect of different surface treatments on the repair shear bond strength of aged resin composites.

Materials and Methods:

Forty cylindrical-shaped specimens were treated from each material: Tetric Evo Ceram, Neo Spectra, and Filtek Ultimate Universal Restorative and allocated into four groups according to the surface treatment planned to use: Group 1: diamond, Group 2: silica coating, Group 3: carbide burs, and Group 4: control group. Following the surface treatment, composites were repaired with flowable resins. The shear bond strength was tested using a universal testing machine at a crosshead speed of 0.5 mm/min. The fracture mode was assessed under 50× magnification. The data were analyzed statistically using a two-way analysis of variance (ANOVA) test followed by a one-way ANOVA test. Multiple comparison procedures were performed using Tukey’s test. The level of significance was set at P < 0.05.

Results:

The lowest mean value of the shear bond strength was for the Filtek Ultimate Universal Restorative in the control group, whereas the highest mean value was in the silica group. Silica and carbide groups had significantly higher mean values of the shear bond strength than diamond and control groups in Tetric EvoCeram and Filtek Ultimate Universal Restorative. In contrast, in Neo Spectra St HV, the carbide group had a higher mean value but was not statistically significant.

Conclusion:

Combinations of mechanical and chemical retentive systems enhance the shear bond strength of the repair composite to the aged composite. Among the different surface treatments employed in this study, silica and carbide groups show higher repair bond strength of new composite to aged composite.

Meta-analytical analysis on components released from resin-based dental materials

OBJECTIVES

Resin-based materials are applied in every branch of dentistry. Due to their tendency to release substances in the oral environment, doubts have been raised about their actual safety. This review aims to provide a comprehensive analysis of the last decade literature regarding the concentrations of elutable substances released from dental resin-based materials in different type of solvents.

MATERIALS AND METHODS

All the literature published on dental journals between January 2010 and April 2022 was searched using international databases (PubMed, Scopus, Web of Science). Due to strict inclusion criteria, only 23 papers out of 877 were considered eligible. The concentration of eluted substances related to surface and volume of the sample was analyzed, considering data at 24 h as a reference. The total cumulative release was examined as well.

RESULTS

The most eluted substances were HEMA, TEGDMA, and BPA, while the less eluted were Bis-GMA and UDMA. Organic solvents caused significantly higher release of substances than water-based ones. A statistically significant inverse correlation between the release of molecules and their molecular mass was observed. A statistically significant positive correlation between the amount of released molecule and the specimen surface area was detected, as well as a weak positive correlation between the release and the specimen volume.

CONCLUSIONS

Type of solvent, molecular mass of eluates, and specimen surface and volume affect substances release from materials.

CLINICAL RELEVANCE

It could be advisable to rely on materials based on monomers with a reduced elution tendency for clinical procedures.

The effects of polymerization mode and layer thickness on monomer released from bulk fill composite resins

Background

Residual monomers released from composite resins have cytotoxic, mutagenic, and estrogenic effects. Mode of polymerization and application thickness are important for monomer release.

Aims

The aim of this study was to investigate the effects of different modes of a third-generation light-curing unit (LCU) and layer thickness on residual monomer released from two different bulk-fill composite resins. A total of 80 samples were prepared for each bulk-fill composite using a mold. Each bulk-fill composite was divided into four groups according to polymerization mode (standard and extra power) and layer thickness (2 and 4 mm). In addition, four groups were divided into four subgroups according to time periods (1 h, 24 h, 3 days, and 7 days).

Methods and Material

The samples were polymerized with VALO LED device. The amount of residual monomer was measured with High-Performance Liquid Chromatography (HPLC). All statistical analyses were processed using SPSS Version 23.0. The normal distribution of data was confirmed using Kolmogorov-Smirnov Normal Distribution Test and Shapiro-Wilk Normal Distribution Test. When the distribution was normal, parametric tests, Student's t test and one-way ANOVA, were used. When the distribution was not normal, non-parametric tests, Mann-Whitney U test, and Kruskal-Wallis testwere used.

Results

It was found that the standard mode of LCU produced lower amounts of TEGDMA, Bis-GMA, and UDMA in both composite materials. In addition, when the layer thickness increased, TEGDMA, Bis-GMA, and UDMA releases increased, too.

Conclusions

This study revealed that the amount of residual monomers released from bulk-fill composites was affected by layer thickness and polymerization time.