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.

The effectiveness of erbium: Yttrium-aluminum-garnet laser on enamel conditioning: An In vitro study.

OBJECTIVES: The purpose of this in vitro study was to investigate the effect of three different enamel surface conditioning procedures on the bonding strength of two resin-based filled fissure sealants. MATERIAL AND METHODS: Freshly extracted, 48 third molar teeth were used in this study. Teeth were randomly divided into three main groups as the phosphoric acid etched, erbium: Yttrium-aluminum-garnet (ER: YAG) laser etched, and the phosphoric acid plus ER: YAG laser-etched groups. The main groups further divided into two subgroups as Clinpro or Fissurit FX applied. After preparation of the enamel surfaces and application of the sealants, the samples were subjected to shear bond strength test. RESULTS: According to statistical analysis with one-way ANOVA, the bonding strength values of the phosphoric acid groups were found significantly higher than those values obtained from the ER: YAG laser and ER: YAG laser plus phosphoric acid groups (P < 0.001). CONCLUSION: As a result of the study, it has been concluded that the laser application alone has no additional benefit to the acid application in terms of bonding strength.

Antioxidant and renoprotective effects of paricalcitol on experimental contrast-induced nephropathy model.

OBJECTIVES: The aim of the study was to assess the effect of paricalcitol on the experimental contrast-induced nephropathy (CIN) model. We hypothesised that paricalcitol may prevent CIN. METHODS: 32 Wistar albino rats were divided into four groups (n=8 each): control group, paricalcitol group, CIN group and paricalcitol plus CIN group. Paricalcitol (0.4 µg kg(-1) day(-1)) was given intraperitoneally for 5 consecutive days prior to induction of CIN. CIN was induced at day 4 by intravenous injection of indometacin (10 mg kg(-1)), Nω-nitro-L-arginine methyl ester (L-NAME, 10 mg kg(-1)) and meglumine amidotrizoate (6 ml kg(-1)). Renal function parameters, oxidative stress biomarkers, histopathological findings and vascular endothelial growth factor (VEGF) immunoexpression were evaluated. RESULTS: The paricalcitol plus CIN group had lower mean serum creatinine levels (p=0.034) as well as higher creatinine clearance (p=0.042) than the CIN group. Serum malondialdehyde and kidney thiobarbituric acid-reacting substances levels were significantly lower in the paricalcitol plus CIN group than in the CIN group (p=0.024 and p=0.042, respectively). The mean scores of tubular necrosis (p=0.024), proteinaceous casts (p=0.038), medullary congestion (p=0.035) and VEGF immunoexpression (p=0.018) in the paricalcitol plus CIN group were also significantly lower. CONCLUSION: This study demonstrates the protective effect of paricalcitol in the prevention of CIN in an experimental model.