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This study investigated the effect of peroxide bleaching gel on the durability of the adhesive bond between composite material, enamel, and dentin created with the etch-and-rinse adhesive Gluma Comfort Bond (GLU) and with the self-etch adhesives Clearfil SE Bond (CLE), Adper Prompt (ADP), and iBond (IBO). The adhesives were applied to flattened enamel and dentin of extracted human molars and built up with a microhybrid composite (Charisma). After 25 eight-hour cycles of bleaching with a 20% carbamide peroxide bleaching gel (Opalescence PF 20), the shear bond strength was measured and compared with one-day and two-month control specimens stored in water. The data were analyzed using nonparametric Mann-Whitney and Kruskal-Wallis statistics (p<0.05). Detailed fractographic analysis was performed using scanning electron microscopy. The bleaching gel significantly decreased the bond strength on both enamel and dentin for the simplified single-step self-etch adhesives ADP and IBO and markedly affected a fracture pattern of ADP specimens at the periphery of their bonded area. The results of our study indicate that the durability of adhesive restorations can be detrimentally influenced by carbamide peroxide bleaching and that different adhesives show varying sensitivity levels to the bleaching gel.

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This study investigated formation of protective deposits on the enamel surface after application of several anti-erosive toothpastes with different active ingredients. NaF-containing Sensodyne Pronamel, SnCl /F-based Elmex Erosion Protection and calcium phosphate-based BioRepair Plus Sensitivity Control, SensiShield and Enamel Care toothpastes with claimed anti-erosive properties were tested. Artificial saliva and Elmex Erosion Protection mouth rinse served as control groups. The toothpastes were applied 30 times by a toothbrush for 2 min per day, mouth rinse for 30 s on polished enamel of thirty five human molars (n = 5) with series of five rhomboid-shaped indents of various length prepared by a Knoop indentor. After 15 and 30 applications, the shape of the indents and surface morphology was characterised using light and scanning electron microscopy. At the end of treatment, the samples were exposed to 0.2 wt. % citric acid (pH 3.30) to test resistance of the treated enamel to erosion. Pronounced differences were observed between protective properties of the toothpastes. While Sensodyne Pronamel and BioRepair Plus Sensitivity Control did not produce any protective deposits, Enamel Care formed a compact layer of deposits which protected the enamel surface against erosion. With Elmex Erosion Protection and SensiShield fractured indent edges and scratches on the treated enamel suggested that their abrasive properties prevailed over ability of active ingredients to form deposits. These results revealed that toothpastes with strong potential to form acid-resistant deposits on the enamel surface and of low abrasivity should be used for effective prevention of enamel erosion. SCANNING 38:380-388, 2016. © 2015 Wiley Periodicals, Inc.

Negative thixotropic behavior in a ueous glycerol solutions of partially hydrolyzed polyacrylamide was studied at various concentrations of Na' , Ca2+ and A1 chlorides. A decrease in critical shear stresses and more intensive negative thixotropic behavior observed in the presence of multivalent cations were explained in terms of their stronger charge screening effect.This effect suppresses intermolecular electrostatic repulsions, which act against association of polymer molecules and, thus, against the occurrence of negative thixotropy. 9, CaC12 (a), 0.45 x 448 Bradna, Quadrat, Titkova, Dupuis Acta Polymer., 48,446-449 (1997) Acta Polymer., 48,446-449 (1997) The influence of multivalent cations on negative thixotropy in aqueous glycerol solutions ...

Dental composite materials often contain monomers with bisphenol A (BPA) structure in their molecules, e.g. bisphenol-A glycidyl dimethacrylate (Bis-GMA). In this study, it was examined whether dental restorative composites could be a low-dose source of BPA or alternative bisphenols, which are known to have endocrine-disrupting effects. Bis-GMA-containing composites Charisma Classic (CC) and Filtek Ultimate Universal Restorative (FU) and “BPA-free” Charisma Diamond (CD) and Admira Fusion (AF) were examined. Specimens (diameter 6 mm, height 2 mm, n=5) were light-cured from one side for 20 s and stored at 37 °C in methanol which was periodically changed over 130 days to determine the kinetics of BPA release. BPA concentrations were measured using a dansyl chloride derivatization method with liquid chromatography – tandem mass spectrometry detection. The amounts of BPA were expressed in nanograms per gram of composite (ng/g). BPA release from Bis-GMA-containing CC and FU was significantly higher compared to “BPA-free” CD and AF. The highest 1-day release was detected with FU (15.4±0.8 ng/g), followed by CC (9.1±1.1 ng/g), AF (2.1±1.3 ng/g), and CD (1.6±0.8 ng/g), and the release gradually decreased over the examined period. Detected values were several orders of magnitude below the tolerable daily intake (4 µg/kg body weight/day). Alternative bisphenols were not detected. BPA was released even from “BPA-free” composites, although in significantly lower amounts than from Bis-GMA-containing composites. Despite incubation in methanol, detected amounts of BPA were substantially lower than current limits suggesting that dental composites should not pose a health risk if adequately polymerized.

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