Development of novel remineralising antibacterial dental composite

The most common current cause of composite restoration failure is bacterial microleakage. This is the passage of bacteria between the tooth and restoration and results in continuing dentine de-mineralisation and disease. The aim of this study was therefore to develop a dental composite with re-mineralising and anti-bacterial components. Methods: Urethane dimethacrylate: poly(propylene glycol) dimethacryate (3:1) was mixed with 5 wt% 2-hydroxyethyl methacrylate, 1 wt% photoinitiator (camphorquinone), and 1 wt% accelerator (N(p-tolyl)glycine-glycidyl methacrylate). This was combined with dental glass particles mixed with anti-bacterial polylysine (0 or 5 wt%) and mono and tri calcium phosphate (each at 0 or 20 wt%) in a powder to liquid ratio of 4:1. Light cured composite discs (10 mm diameter, 1 mm thick, n=8) were prepared and stored dry, in distilled water (DW), simulated body fluid (SBF) or Artificial Saliva. Surfaces were examined by Scanning-electron microscopy (SEM), Energy-dispersive X-ray (EDX) spectroscopy and Raman microscopy after 7 days storage. Mass and volume changes in DW and SBF were determined gravimetrically at 12-weeks storage. Polylysine release into water was assessed using Trypan Blue dye and visible absorbance spectroscopy. Results: Various calcium phosphates precipitated on the material surfaces and cores but apatite was found only on the surface of samples containing both calcium phosphates and Polylysine that were stored in SBF. This formula showed greater increase in mass and volume change, and the highest Polylysine release. Composite containing both calcium phosphates (MCPM and TCP) and polylysine showed the highest water sorption potential and therefore more precipitation and increase in volume. Also, adding both MCPM and TCP slightly enhanced the release of the antibacterial (polylysine). Significance: Formulations with MCPM, TCP and polylysine through water sorption induced expansion; re-mineralisation and anti-bacterial release have potential to reduce recurrent caries

The metal – ionic liquid interface as characterized by impedance spectroscopy and in-situ scanning tunneling microscopy

We summarize our results of electrochemical measurements carried out on inert or close-to-inert metals in ionic liquids, with the aim to explore the metal | ionic liquid interface structure. To this we used electrochemical methods: cyclic voltammetry, impedance spectroscopy, potential of zero total charge measurements and structure-sensitive techniques, such as in-situ scanning tunneling spectroscopy. The studied systems were mostly single crystals of noble metals in imidazolium-based ionic liquids. The two main findings are: (i) in the potential window where no Faradaic reactions occur, the interfacial capacitance exhibits a frequency dependence due to double-layer rearrangement processes and (ii) in certain cases ordered anion and cation structures exist at the interface

Cu-nanoclusters produced on AuCu-Alloys with an electrochemical scanning tunneling microscope

Cu-nanoclusters can be produced in an electrochemical environment by tip-induced metal deposition using an electrochemical scanning tunneling microscope (EC-STM). These clusters, consisting of 100-1000 atoms only, show a surprising stability against anodic oxidation. The clusters, which are 2-3 atomic layers in height dissolve slowly when the applied potential is increased step by step to 200 mV positive of the reversible Nernst potential for ``normal{''} copper dissolution. The presented work gives evidence that the unusual stability of the clusters could be a consequence of interfacial alloying between the cluster and the underlying substrate. In order to study these effects Cu-nanoclusters have been produced on pure gold substrates and on carefully prepared Au3Cu(111)-substrates. This work compares the results obtained on both substrates