Background. Severe contamination of dental unit waterlines was found in healthcare settings. The benefits of decontamination methods are controversial. The aim of this review was to systematically evaluate disinfection methods in contamination control of dental unit waterlines. Methods. The terms ‘dental unit waterline(s) or DUWL(s) or dental unit water line(s)’ were searched through PubMed, Cochrane Library, Embase, Web of Science and Scopusup to 31 May 2021. The DUWLs’ output water was incubated on R2A agar at 20–28 °C for 5–7 days to evaluate heterotrophic mesophilic bacteria. The risk of bias was evaluated by a modified Newcastle-Ottawa quality assessment scale. Results. Eighteen papers from the literature were included. One study indicated that water supply played a crucial role in disinfecting DUWLs. Three studies indicated that flushing decreased bacteria counts but did not meet the American CDC standard (500 c.f.u. ml−1). All chlorine- and peroxide-containing disinfectants except sodium hypochlorite in one of 15 studies as well as three mouthrinses and citrus botanical extract achieved the standard (≤500 c.f.u. ml−1). The included studies were of low (1/18), moderate (6/18) and high (11/18) quality. Conclusion. Independent water reservoirs are recommended for disinfecting DUWLs using distilled water. Flushing DUWLs should be combined with disinfections. Nearly all the chlorine-, chlorhexidine- and peroxide-containing disinfectants, mouthrinses and citrus botanical extract meet the standard for disinfecting DUWLs. Alkaline peroxide would lead to tube blockage in the DUWLs. Regularly changing disinfectants can reduce the risk of occurrence of disinfectant-resistant strains of microbes.

Friction and wear properties of hot working die steel at above 800 °C are of particular interest for high temperature applications. Here, novel AlCoCrFeNiWx high-entropy alloy (HEA) coatings have been fabricated on the surface of hot working die steel by laser cladding. The effects of the as-prepared AlCoCrFeNiWx HEA coatings on the microstructure and high temperature friction and wear behavior of hot working die steel are investigated through scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS). Having benefited from the formation of W-rich intermetallic compounds after the addition of W elements, the high temperature wear resistance of the coatings is obviously improved, and friction coefficient shows a large fluctuation. The microstructural characteristics of the AlCoCrFeNiWx HEA coatings after the high temperature wear resistance test shows a highly favorable impact on microstructure stability and wear resistance, due to its the strong lattice distortion effect of W element on BCC solid solutions and the second phase strengthening of the W-rich intermetallic compounds. These findings may provide a method to design the high temperature wear resistant coatings.

The specular gloss of metallic coatings from the automotive industry can be well measured by current glossmeters when the geometry is appropriately chosen from 20°, 60°, and 85°based on the gloss levels observed. However, the measurements are discontinuous and even nonmonotonic at the breakpoints dividing samples into different gloss levels in the whole range, which causes confusion and inconvenience for industry applications. In this study, attempts were made to link the measurements at the three geometries to be continuous monotonically and in the meanwhile to improve the accuracy of estimating visual gloss. A psychophysical experiment based on a magnitude method was carried out to assess the gloss of metallic coatings with different colors and textures. The visually scaled gloss data were compared with spectrophotometric measurements and instrumental specular gloss values under different geometries. With different weighing coefficients for measurements at individual geometries depending on the gloss levels, a model was proposed to describe the visual surface gloss of metallic coatings comprehensively via a practical metric based on the geometry-dependent measurements. In this way, each sample would have a unique overall gloss value highly correlated with its perceptual evaluation over the entire gloss range.