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 (α = .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.

The environmental impact of governance: a system-generalized method of moments analysis.

To investigate the role of governance on environmental quality, two hypotheses are developed; when good governance practices dominate governance structures, then improvement in governance levels leads to better environmental outcomes, and when bad governance practices dominate governance structures, then improvement in governance levels leads to deterioration in environmental outcomes. To test these hypotheses for 115 countries clustered as high, middle, and low income over the period of 2000 to 2015, system generalized method of moments is employed. The results show that an improvement in governance increases environmental quality in high income countries, while it decreases environmental quality in middle- and low-income countries. We concluded that high-income countries should improve governance structures to get better environmental outcomes without changing their environment-oriented policies and governance practices, and middle- and low-income countries should bring in structural changes to their governance systems by prioritizing environmental outcomes over economic outcomes for improving environmental quality.

The role of financial development on carbon emissions: a meta regression analysis.

The study analyzes the role of financial development on CO2 emissions based on the primary studies in the existing literature. However, the heterogeneity in reported effect size estimates of the primary studies complicates to test the competing hypotheses for the role of financial development on CO2 emissions. The paper tries to determine and quantify the representative empirical genuine effect of financial development on CO2 emissions, if any. To address the issue, a meta-regression analysis has been carried out for 275 estimation results from 72 primary studies. We have found a substantial publication selection bias in the literature due to the design characteristics of the primary studies. The results suggest the presence of an authentic positive empirical effect of financial development on CO2 emissions beyond publication selection bias. Hence, financial development leads to environmental degradation. The effect of financial development on carbon emissions changes both in magnitude and direction depending on which financial development indicator is used, which estimation technique is employed, which countries or region are included and which time period is analyzed.

Bond strength of self-adhesive resin cement to root dentin. Comparison of photon-initiated photoacoustic streaming technique with needle and ultrasonic irrigation.

OBJECTIVE: The aim of this study was to investigate the effects of photon-initiated photoacoustic streaming (PIPS) with various irrigating solutions on the bond strength of a self-adhesive resin cement to root dentin. MATERIALS AND METHODS: Seventy-two mandibular premolar roots were divided into six groups after post space preparation and treated with a needle irrigation with distilled water and NaOCl, ultrasonic irrigation with NaOCl, PIPS with NaOCl, PIPS with EDTA and PIPS with distilled water at 0.3 W, 15 Hz and 20 mJ per pulse for 60 s. Fiber posts were cemented with a newly marketed, self-adhesive resin cement. The data obtained from the push-out tests were analyzed using analysis of variance (ANOVA) and LSD post-hoc tests (p = 0.05). RESULTS: PIPS with distilled water resulted in higher push-out values than those of needle (with both distilled water and NaOCl) and ultrasonic irrigation (p < 0.05). CONCLUSIONS: The use of PIPS may provide higher bond strength of self-adhesive resin cement to root dentin than needle and ultrasonic irrigation techniques.

Comparison of bond strength of self-etch adhesive to pulp chamber dentin after placement of calcium hydroxide and various antibiotic pastes.

OBJECTIVE: The aim of this study was to evaluate the effect of calcium hydroxide, double antibiotic paste (DAP) and triple antibiotic paste (TAP) with minocycline, cefaclor and amoxicillin on the micro tensile bond strength (µTBS) of self-etch adhesive to pulp chamber dentin. MATERIALS AND METHODS: Sixty mandibular first molars were cut horizontally and randomly divided into a control group and five experimental groups, which received an intra-canal dressing, as follows: calcium hydroxide, DAP, TAP with minocycline, TAP with cefaclor and TAP with amoxicillin. After storing the specimens for 4 weeks, the medicaments were removed by irrigation with 10 mL each of the following solution: 2.5% NaOCl, 17% EDTA and distilled water. A self-etch adhesive (Clearfil S3 Bond, Okayama, Japan) was applied and composite resin (Clearfil Majesty Posterior, Kuraray Medical Inc., Japan) was placed into the cavity. A µTBS test was performed on each specimen using a universal test machine. RESULTS: The DAP reduced the µTBS of self-etch adhesive compared to the control group, calcium hydroxide and TAP with minocycline and with cefaclor (p < 0.05). However, the other medicaments did not result in a decreased µTBS of self-etch adhesive to pulp chamber dentin as compared to the control group (p > 0.05). CONCLUSIONS: The use of DAP resulted in a reduced µTBS of self-etch adhesive to pulp chamber dentin.