Objective: The effect of different staining solutions and a bleaching procedure on color stability and surface roughness of a nanohybrid resin composite were evaluated with or without liquid resin polishing (RP). Materials and Methods: Ninety-six disc-shaped resin composite specimens (A1 Shade, Z550 Filtek 3M ESPE, St. Paul, MN, USA) were prepared and divided randomly into two groups (n = 48). Liquid RP (BisCover LV, Bisco Inc., Schaumburg, IL, USA) was applied in one group (RP) and not in the other (P). Specimen color and surface roughness were determined using a colorimeter and profilometer, respectively. After baseline measurements, each group was divided into four subgroups (n = 12) for immersion in a control (distilled water) or three different staining solutions (ice tea, red wine, and cola) for 1 week. Color and surface roughness were then reevaluated. After measurements, all specimens were bleached using a 35% hydrogen peroxide gel. The color and surface roughness of the specimens were reevaluated. Statistical Analysis: Data were subjected to an analysis of variance for repeated measurements among the groups (P < 0.05). Results: Staining and bleaching did not change the surface roughness of the RP and P groups (P > 0.05). Discoloration in the red wine group was higher than for the other staining solutions for the RP (P < 0.001) and P groups (P = 0.018). Conclusion: Application of liquid RP did not enhance the color stability and surface roughness of the composite resin restoration.

The aim of this study was a comprehensive evaluation and comparison of the physical and mechanical properties of a newly developed nano-sized hydroxyapatite fiber-reinforced composite with other fiber-reinforced and particle-filled composites. Commercially available eight composite resins (3 fiber-reinforced and 5 particle-filled) were used: Fiber-reinforced composites: (1) NovaPro Fill (Nanova): newly developed nano-sized hydroxyapatite fiber-reinforced composite (nHAFC-NF); (2) Alert (Pentron): micrometer-scale glass fiber-reinforced composite (µmGFC-AL); (3) Ever X Posterior (GC Corp): millimeter-scale glass fiber-reinforced composite (mmGFC-EX); Particle-filled composites: (4) SDR Plus (Dentsply) low-viscosity bulk-fill (LVBF-SDR); (5) Estelite Bulk Fill (Tokuyama Corp.) low-viscosity bulk-fill (LVBF-EBF); (6) Filtek Bulk Fill Flow (3M ESPE) low-viscosity bulk-fill (LVBF-FBFF); (7) Filtek Bulk Fill (3M ESPE) high-viscosity bulk-fill (HVBF-FBF); and (8) Filtek Z250 (3M ESPE): microhybrid composite (µH-FZ). For Vickers microhardness, cylindrical-shaped specimens (diameter: 4 mm, height: 2 mm) were fabricated (n = 10). For the three-point bending test, bar-shaped (2 × 2 × 25 mm) specimens were fabricated (n = 10). Flexural strength and modulus elasticity were calculated. AcuVol, a video image device, was used for volumetric polymerization shrinkage (VPS) evaluations (n = 6). The polymerization degree of conversion (DC) was measured on the top and bottom surfaces with Fourier Transform Near-Infrared Spectroscopy (FTIR; n = 5). The data were statistically analyzed using one-way ANOVA, Tukey HSD, Welsch ANOVA, and Games–Howell tests (p < 0.05). Pearson coefficient correlation was used to determine the linear correlation. Group µH-FZ displayed the highest microhardness, flexural strength, and modulus elasticity, while Group HVBF-FBF exhibited significantly lower VPS than other composites. When comparing the fiber-reinforced composites, Group mmGFC-EX showed significantly higher microhardness, flexural strength, modulus elasticity, and lower VPS than Group nHAFC-NF but similar DC. A strong correlation was determined between microhardness, VPS and inorganic filler by wt% and vol% (r = 0.572–0.877). Fiber type and length could affect the physical and mechanical properties of fibers containing composite resins.

Purpose: To evaluate the wetting ability and the microtensile bond strength of adhesive systems in various depths of dentin. Materials and Method: 48 extracted human molars cut in half in buccolingual direction. Buccal and lingual surfaces were used to obtain deep (n = 48) and superficial (n = 48) dentin. Groups were divided into 4 subgroups: Self-etch (CSE), etch&rinse (SB), multi-mode self-etch (SAU) and multimode etch&rinse (EAU) adhesive systems. 3 consecutive contact-angle measurements were obtained: T0- 3 μl drop of distilled water on dentin; T1-Droplet of the adhesive; T2- Distilled water after polymerization of the adhesive. After composite build-ups, microtensile measurements were performed. Contact angle data were analysed with analysis of variance for repeated measures. Bond strength data were analyzed by repeated measures analysis of variance, comparisons were made according to the logarithmic values (p < 0.05). Results: The difference between groups was not significant regardless of dentin depth for all measurements (p < 0.05). All groups except CSE enhanced the wetting ability of the adhesive but reduced the wetting ability of distilled water after application of the adhesive (p < 0.05). Regarding adhesive systems, the groups showed no significant difference between bond strengths to various depths of dentin except SAU (p > 0.05); in SAU, bond strength to deep dentine were significantly higher than superficial dentin (p < 0.05). Regarding adhesives’ bond strength, CSE showed significantly greater values than the other groups (p < 0.05). Conclusion: The cavity depth does not affect the bonding ability for all adhesive systems; self-etch adhesive systems might be a better choice since different adhesives may influence the wetting ability and microtensile bond strength of the dentin substrates.

This in vitro study evaluated the volumetric change (VC) and gap formation (GF) in Class V composite restorations after light-curing and aging. Thirty-six extracted human premolars were used. Standardized Class V cavities (3 mmx3 mmx1.5 mm) were prepared. G-Premio Bond was applied. The teeth were randomly assigned into six groups (n = 6): Group FZ: Filtek Z250(microhybrid), Group SP: SDR Plus Bulk Fill Flowable (low-viscosity bulk-fill), Group EB: Estelite Bulk Fill Flow (low-viscosity bulk-fill), Group GI: G-aenial Universal Injectable (highly-filled low-viscosity), Group AF: Admira Fusion (ormocer), Group SX: Solare X (nanohybrid). Each specimen was scanned four times with micro-CT (SkyScan 1174v2, Belgium): after cavity preparation, before and after light-curing, and after aging. The VC (%) and GF (mm³) parameters were quantified and analysed. Then, VC after light-curing was verified with AcuVol video image analyser (n = 6). The specimens were submitted to 10,000 thermocycles (5–55 °C) and 100,000 load cycles (50N). The data were statistically analysed using the Kruskal-Wallis, Wilcoxon and Dunn tests (p < 0.05). After light-curing, Group AF and FZ showed significantly lower VC than Group GI. Group GI showed significantly higher total GF than Group AF, EB, FZ and SX. Group GI showed significantly higher GF than Group AF, EB and FZ in cervical region. After aging, a significant increase in the volume of the gap (VG) in cervical region was found for Group FZ and GI (p < 0.05). After light-curing, ormocer and microhybrid composites exhibited lower VC and GF than highly-filled low-viscosity composites. After aging, an increase in VG was observed for microhybrid and highly-filled low-viscosity composites for cervical region.

Objectives: This study evaluated stress distrubitions formed by oblique forces in dental hard tissues, base materials and restorations of endodontically treated permanent mandibular first molars that were restored with different base materials and direct composite restorations by using 3D-FEA method.Materials and Methods: For two different restorative approaches; an MO cavity design and a MOD cavity design was created. Then root canal obturation was modeled. Composite resin (CR), conventional glass ionomer cement (GIC), fiber reinforced composite resin (FRCR), resin modified glass ionomer cement (RMGIC), flowable composite (FC), and bulk-fill composite resin (BF) were used as base materials. Von Mises, compressive and tensile stresses in enamel, dentin, base materials and final restoration were analyzed using finite element stress analysis method.Results: Regarding the resulting stresses, CR caused highest stresses and RMGIC caused lowest stresses in enamel, base material, and final restoration. RMGIC caused highest stresses and CR caused lowest stresses in dentin. It was noted that MOD cavity design caused more stress than MO cavity design for all analyzed materials.Conclusions: Materials with elastic moduli similar to dentin; FRCR and GIC, may be better choice to avoid high stresses within the tooth and restoration.