The removal or modification of smear layers that cover the dentin is critical to allow the penetration of adhesive molecules and to ensure a strong bond between resin and dentin. Aiming to establish a model for clinically-relevant dentin-bond testing, we evaluated the effects of smear layers created by abrasives having similar coarseness (180-grit SiC paper; fine-grit diamond bur) and application modes (single application; double application) on the microtensile bond strengths (µTBS) of two currently available universal adhesives (G-Premio Bond; Scotchbond Universal Adhesive) and a two-step self-etch adhesive (Clearfil Megabond 2). Sixty extracted human third molars were used for the μTBS test. Data were analyzed by three-way ANOVA and Tukey’s test (α = 0.05). Fracture modes were determined using stereomicroscopy. An additional 24 third molars were prepared for observation of the resin–dentin interface by TEM and adhesive-smear layer interaction by SEM. μTBS was significantly affected by the adhesives and their application modes (p < 0.001), implying that the double application of universal adhesives should be recommended to improve their performance. The effect of smear layers was not significant (p > 0.05), indicating that 180-grit SiC papers could be used to prepare dentin as a substitute for fine-grit diamond burs for dentin-bond testing in laboratory settings.

Objective To evaluate the shade matching ability of a novel supra‐nano filled esthetic resin composite employing structural color technology using simplified simulated clinical cavities. Filler morphology and light transmittance characteristics were also evaluated. Materials and Methods One‐hundred and twenty frames of resin composite were built in A1, A2, A3, and A4 shades to simulate Class I cavities (diameter = 4 mm, height = 2 mm). For each shaded frame, cavities were filled with three different types of filler containing resin composites (n = 10): supra‐nano filled (SN filled) resin composite, microhybrid filled (MH filled) resin composite, and clustered‐nano filled (CN filled) resin composite. Color parameters were calculated using CIELAB (△Eab) and CIEDE2000 (△E00). Data were analyzed using one‐way analysis of variance (ANOVA), followed by Duncan's test (α = .05). Filler morphology and light transmittance characteristics were measured to explore the role of structural color on shade matching. Results △Eab and △E00 of SN filled resin composite were significantly lower in A2, A3, and A4 shades (P < .05). Conclusions The SN filled resin composite showed better shade matching with A2, A3, and A4 shades of resin composite frames compared to MH filled resin composite, and CN filled resin composite. Clinical Significance Universal‐shade resin composites, which were expected to match nearly all shades, simplify the restorative procedure. Resin composite, which contained spherical supra‐nano filler particles, could contribute most to its shade matching by stimulating structural color. Structural color technology may provide additional benefits for shade matching of resin composites.

Oncolytic virotherapy is a novel approach to cancer therapy. Ad-fosARE is a conditionally replicative adenovirus engineered by inserting AU-rich elements (ARE) in the 3’-untranslated region of the E1A gene. In this study, we examined the oncolytic activity of Ad-fosARE and used it in a synergistic combination with the chemotherapeutic agent paclitaxel (PTX) for treating cancer cells. The expression of E1A was high in cancer cells due to stabilized E1A-ARE mRNA. As a result, the efficiency of its replication and cytolytic activity in cancer cells was higher than in normal cells. PTX treatment increased the cytoplasmic HuR relocalization in cancer cells, enhanced viral replication through elevated E1A expression, and upregulated CAR (Coxsackie-adenovirus receptor) required for viral uptake. Furthermore, PTX altered the instability of microtubules by acetylation and detyrosination, which is essential for viral internalization and trafficking to the nucleus. These results indicate that PTX can provide multiple advantages to the efficacy of Ad-fosARE both in vitro and in vivo, and provides a basis for designing novel clinical trials. Thus, this virus has a lot of benefits that are not found in other oncolytic viruses. The virus also has the potential for treating PXT-resistant cancers.

This study evaluated an experimental two-step self-etch adhesive (BZF-29, BZF) by comparing it with a reference two-step self-etch adhesive (Clearfil Megabond 2, MB) and a universal adhesive (G-Premio Bond, GP) for microtensile bond strength (μTBS) and resin-dentin interfacial characteristics. Twenty-four human third molars were used for the μTBS test. Bonded peripheral dentin slices were separated to observe the resin-dentin interface and measure the adhesive layer thickness with SEM. μTBS data of the central beams were obtained after 24 h and 6 months of water storage. Fracture modes were determined using a stereomicroscope and SEM. Nine additional third molars were used to determine the elastic modulus (E) employing an ultra microhardness tester. Water storage did not affect μTBS of the tested adhesives (p > 0.05). μTBS of BZF and MB were similar but significantly higher than GP (p < 0.05). BZF achieved the highest adhesive layer thickness, while GP the lowest. E of BZF and MB were comparable but significantly lower than GP (p < 0.05). Except for GP, the predominant fracture mode was nonadhesive. The superior bonding performance of BZF and MB could be attributed to their better mechanical property and increased adhesive thickness imparting better stress relief at the interface.

Abstract

The complex, dynamic, and hydrated microstructures of human dentin serve as the major determinant for the restorative performance of biomaterials. This study aimed to evaluate the mechanical properties of human dentin under different hydration conditions. The occlusal dentin of five third molars was exposed and cut into 1 mm2 dentin slabs. The slabs were then polished and further cut into 1 mm2 dentin beams and stored in distilled water. Two beams/tooth were used for testing their hardness (H) and elastic modulus (E) at 5 min (baseline), 1 h, and 24 h after dehydration (23 °C and 30% RH), and also for measuring weight at following dehydration times: 0 min, 5 min, 1 h, and 24 h. Five additional molars were employed to prepare 0.4 mm2 dentin beams (3/tooth) for determining ultimate tensile strength (UTS) at 5 min (baseline), 1 h, and 24 h post-dehydration. Statistical significance was set at α = 0.05. Dehydration time significantly affected H, E, weight-loss, and UTS of dentin (p < 0.05). H and E values showed a strongly positive and significant correlation (r > 0.5, p < 0.05). Dehydration can substantially modify the mechanical properties of dentin, leading to misinterpretation of restorative outcomes in vitro.

This study evaluated the antibacterial activity of colloidal platinum nanoparticles (CPNs) toward Streptococcus mutans (S. mutans) viability. S. mutans 109c was treated with water and three CPN solutions at 37°C for 24 h (i.e., control, PAA-Pt, C-Pt, C-CyD-Pt). Dilution series (10 -1 -10 -5 ) were prepared using brain heart infusion (BHI) broth for all samples, and a 100 µL suspension of each dilution was spread onto a BHI agar plate. Colony-forming units (CFU/mL) were determined after 24 h. The effects of CPNs on S. mutans survival and biofilm formation were investigated using fluorescence and scanning electron microscopies. The antibacterial rate of S. mutans increased with increasing concentrations of all three CPNs, with PAA-Pt nanoparticles exhibiting the highest antibacterial efficacy. CPNs were found to reduce S. mutans growth and inhibit biofilm formation remarkably.