The aim of this article is to compare the effects of 1.5 T and 3 T MRI on microleakage of amalgam restorations. A total of 90 extracted molar teeth were used in this study. Amalgam was used to restore standard Class V preparations (5 × 3 × 2 mm). Following the restoration, the teeth were divided into three groups according to magnetic resonance imaging (MRI) protocol (Group I: Control, Group II: 1.5 T MRI, and Group III: 3 T MRI). A total of 6,000 thermal cycles at 5°C–55°C were applied on all samples. Microleakage values were measured in millimeters using the ImageJ program. Microleakage values were higher in the gingival region compared to the occlusal region in all groups and the differences were statistically significant (p < .05). Microleakage values were not statistically different among the groups in the occlusal region (p > .05), while there were statistically significant differences among the groups with respect to microleakage values in the gingival region (p < .01). The highest mean microleakage amount in the gingival region was measured in Group III (1.192 ± 0.941 mm). This was followed by Group II (0.519 ± 0.813 mm) and Group I (0.347 ± 0.726 mm), respectively. Within the limitations of this in vitro study, we observed that higher microleakage values in amalgam restored teeth in which were exposed to MRI procedure. We also found that the teeth exposed to the stronger magnetic field showed higher microleakage amount.

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 aim of this study was to examine the effects of different acidic beverages on the surface hardness of restorative materials which are frequently used in clinical practices. Materials and Methods: In this study, cola, sour cherry juice, apple juice, energy drink and orange juice were used as acidic beverages while two composite resins (Filtek Silorane, Filtek Z-550), one flowable composite (Filtek Ultimate Flowable), one compomer (Dyract Extra) and one resin modified glass ionomer (Fuji II LC) served as restorative materials to be tested. After measuring the initial surface hardness of the samples with Barcol surface hardness tester, each sample was put into acidic beverage for five seconds after which they were placed in artificial saliva for five seconds. This cycle was repeated ten times daily for one month. The control group was stored in the artificial saliva without any exposure to this cycle. At the end of the one-month-period, surface hardness of the restorative materials were measured again. Statistical analysis used: "Repeated Measures Analysis of Variance" and "Tukey's Multiple Range Test" were used for statistical analysis. Results: The restorative materials were affected by the acidic beverages. The liquids used in the study, except the artificial saliva, had statistically similar effects on the surface hardness values of the materials used (p<0.05). Conclusion: In conclusion, the beverages used in this study affected the surface hardness of the restorative materials investigated differently.

Purpose: The aim of this study is to compare the shear bond strength of three high-viscosity bulk-fill composite resins applied as single layers of 4mm thickness and of one microhybrid composite resin applied incrementally with a thickness of 2mm on dentin surfaces prepared with different surface preparation methods. Materials and Methods: A total of 132 caries-free human molars whose dentines had been exposed were used. Three groups, each containing 44 teeth, were formed. The acid group was etched with 32% phosphoric acid; laser group was etched with Er, Cr; YSGG laser and the control group was prepared with silicon carbid paper. Following the application of bonding agent, composite resin materials were applied on teeth using teflon moulds of 4x4mm. The samples were then subjected to shear bond strength tests. Two-way variance analysis and Tukey HSD multiple comparison test were applied on collected data. Results: There was a significant difference between surface treatment methods used regarding shear bond strength (P<0.001). The highest shear bond strength values were detected in the “Acid” group while the lowest shear bond strength values were detected in the “control” group. On the other hand, there was no statistically significant difference among composite resins (P>0.05). Conclusions: Laser etching of the dentin tissues is not as effective as acid etching. Bulk-fill composites had similar effects compared with conventional composite resins with regard to bonding strength. More in vitro studies supported with clinical data are required to investigate the performance of bulk-fill composites and laser.

Objective: The aim of this study is to evaluate the effect of polymerization in different light power modes on the radiopacity of six different composite resins (Filtek Z250, Xtrafil, Tetric N Ceram, SureFil SDR Flow, Nova Compo HF, Grandio Flow). Materials and Methods: Plexiglass molds (8 mm diameter, 2 mm thickness) were used for the preparation of the samples. Totally ten samples were formed for each composite resin (standard mode; n=5 and extra power mode; n=5). A 2-mm-thickness bucco-lingual section was obtained from the extracted premolar tooth for enamel and dentin sample. To evaluate the relationship between the density of the samples and tooth structure, an Al stepwedge was used as a reference. The mean gray values of each composite resin, enamel, dentin and Al stepwedge were calculated with an image analysis program. Data were analyzed with independent sample t test, one way ANOVA and Tukey HSD test. Results: All tested composites met ISO standards. Even if the radiopacity values of tested composites changed according to the light power mode, this change was found to be statistically significant only in SureFil SDR Flow (P=0.037). The difference between the radiopacity values of tested composites in both standard power and extra power mode was statistically significant (P