Multi-scale characterization of Developmental Defects of Enamel and their clinical significance for diagnosis and treatment.

Developmental Defects of Enamel (DDE) such as Dental Fluorosis (DF) and Molar Incisor Hypomineralization (MIH) are a major public health problem. Their clinical aspects are extremely variable, challenging their early and specific diagnosis and hindering progresses in restorative treatments. Here, a combination of macro-, micro- and nano-scale structural and chemical methods, including, among others, Atom Probe Tomography recently applied on tooth enamel, were used to study and compare MIH, DF and healthy teeth from 89 patients. Globally, we show that DF is characterized by an homogenous loss of mineral content and crystallinity mainly disrupting outside layer of enamel, whereas MIH is associated with localized defects in the depth of enamel where crystalline mineral particles are embedded in an organic phase. Only minor differences in elemental composition of the mineral phase could be detected at the nanoscale such as increased F and Fe content in both severe DDE. We demonstrate that an improved digital color measurement of clinical relevance can discriminate between DF and MIH lesions, both in mild and severe forms. Such discriminating ability was discussed in the light of enamel composition and structure, especially its microstructure, organics presence and metal content (Fe, Zn). Our results offer additional insights on DDE characterization and pathogenesis, highlight the potentiality of colorimetric measurements in their clinical diagnosis and provide leads to improve the performance of minimally invasive restorative strategies. STATEMENT OF SIGNIFICANCE: Developmental Defects of Enamel (DDE) are associated to caries and tooth loose affecting billions of people worldwide. Their precise characterization for adapted minimally invasive care with optimized materials is highly expected. Here In this study, first we propose the use of color parameters measured by a spectrophotometer as a means of differential clinical diagnosis. Second, we have used state-of-the-art techniques to systematically characterize the structure, chemical composition and mechanical optical properties of dental enamel teeth affected by two major DDE, Dental Fluorosis (DF) or Molar Incisor Hypomineralization (MIH). We evidence specific enamel structural and optical features for DF and MIH while chemical modifications of the mineral nanocrystals were mostly correlated with lesion severity. Our results pave the way of the concept of personalized dentistry. In the light of our results, we propose a new means of clinical diagnosis for an adapted and improved restoration protocol for these patients.

Antimicrobial and mechanical properties of functionalized textile by nanoarchitectured photoinduced Ag@polymer coating.

The control of microbial proliferation is a constant battle, especially in the medical field where surfaces, equipment, and textiles need to be cleaned on a daily basis. Silver nanoparticles (AgNPs) possess well-documented antimicrobial properties and by combining them with a physical matrix, they can be applied to various surfaces to limit microbial contamination. With this in mind, a rapid and easy way to implement a photoinduced approach was investigated for textile functionalization with a silver@polymer self-assembled nanocomposite. By exposing the photosensitive formulation containing a silver precursor, a photoinitiator, and acrylic monomers to a UV source, highly reflective metallic coatings were obtained directly on the textile support. After assessing their optical and mechanical properties, the antimicrobial properties of the functionalized textiles were tested against Escherichia coli (E. coli) and Candida albicans (C. albicans) strains. In addition to being flexible and adherent to the textile substrates, the nanocomposites exhibited remarkable microbial growth inhibitory effects.

Unravelling kinetic and thermodynamic effects on the growth of gold nanoplates by liquid transmission electron microscopy.

The growth of colloidal nanoparticles is simultaneously driven by kinetic and thermodynamic effects that are difficult to distinguish. We have exploited in situ scanning transmission electron microscopy in liquid to study the growth of Au nanoplates by radiolysis and unravel the mechanisms influencing their formation and shape. The electron dose provides a straightforward control of the growth rate that allows quantifying the kinetic effects on the planar nanoparticles formation. Indeed, we demonstrate that the surface-reaction rate per unit area has the same dose-rate dependent behavior than the concentration of reducing agents in the liquid cell. Interestingly, we also determine a critical supply rate of gold monomers for nanoparticle faceting, corresponding to three layers per second, above which the formation of nanoplates is not possible because the growth is then dominated by kinetic effects. At lower electron dose, the growth is driven by thermodynamic and the formation and shape of nanoplates are directly related to the twin-planes formed during the growth.

One-step UV-induced modification of cellulose fabrics by polypyrrole/silver nanocomposite films.

Cellulose fabrics were coated with polypyrrole-silver (PPy/Ag) nanocomposite films via one pot photopolymerization in aqueous media. This process was optimized for various concentrations of pyrrole/textile weight ratios with fixed molar ratio of [pyrrole]/[AgNO(3)] as 2.5. Simple weight measurements of the fabrics indicated progressive coating of PPy/Ag versus initial pyrrole/fabric weight ratio and photopolymerization time. X-ray diffraction (XRD) data confirm the nano-size (10-30 nm) and metallic state of Ag crystallites. The metallic state of silver particles was also confirmed by X-ray photoelectron spectroscopy (XPS). We demonstrate that UV-induced polymerization of pyrrole in the presence of AgNO(3) is simple and fast compared to chemical oxidative polymerization in the absence of UV light. More importantly, it permits to coat cellulose fabrics in one pot by polypyrrole/Ag nanocomposites films in environmentally friendly aqueous solutions at room temperature.