Search

Abstract The occlusion of dentinal tubules has become a rapid and effective method for treating dentin hypersensitivity. Accurate evaluation of dentin occlusion is critical to illustrate the efficacy of oral care products and to optimize dental therapy in the clinics, which is limited by the conventional two-dimensional (2-D) characterization methods. Here, we demonstrate the visualization of the dentin occlusion via three-dimensional (3-D) characterization using a focused ion beam-scanning electron microscopy (FIB-SEM) tomography. Using the “Slice and View” approach, the material used for occluding dentin tubules is imaged with a very high-resolution voxel (10 nm × 10 nm × 20 nm) from 2-D SEM images and then reconstructed into a 3-D volume, which presents the mode of action of toothpaste for treating dentin hypersensitivity. Meanwhile, quantitative analysis of the depth of occlusion is successfully obtained. This work validates the feasibility of FIB-SEM tomography in the analysis of dentin occlusion within the complicated networks of dentine tubules at the nanoscale, and provides a novel approach to facilitate the research and development of oral care products.

Abstract A deformable microfluidic system and a fluidic dynamic model have been successfully coupled to understand the dynamic fluid–structure interaction in transient flow, designed to understand the dentine hypersensitivity caused by hydrodynamic theory. The Polydimethylsiloxane thin sidewalls of the microfluidic chip are deformed with air pressure ranging from 50 to 500 mbar to move the liquid meniscus in the central liquid channel. The experiments show that the meniscus sharply increased in the first 10th of second and the increase is nonlinearly proportional to the applied pressure. A theoretical model is developed based on the unsteady Bernoulli equation and can well predict the ending point of the liquid displacement as well as the dynamics process, regardless of the wall thickness. Moreover, an overshooting and oscillation phenomenon is observed by reducing the head loss coefficient by a few orders which could be the key to explain the dentine hypersensitivity caused by the liquid movement in the dentine tubules.

Abstract Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) system has become valuable and popular tool for the analysis of biological materials such as dentine structures. According to physiological and anatomical studies, dentine structures are a complicated system containing collagen fibers, nanocrystalline hydroxyapatite, and numerous networks of tubular pores. During a routine FIB milling process, collagen fibers and other organic structures are vaporized, which increases the number of pores on the milled surface of the dentine. This causes the final cross-section to be more porous than the pristine sample. Unfortunately, little attention has been paid to the collagen fiber loss and how to preserve them during a FIB milling process. In this work, we present a novel and simple approach to preserve the organic portions of the dentine structure through metal staining. By using this method, the porosity of the dentine structure after the FIB milling process is significantly reduced similar to the pristine sample. This indicates that the organic portion of the dentine structure is well protected by the metal staining. This approach enables the SEM/FIB system to generate super-high quality SEM images with less ion beam damage; and the SEM images can better reflect the original condition of the dentine structure. Further, serial energy-dispersive X-ray spectroscopy (EDS) mapping of the stained dentine structure is achieved without an additional metal coating; and three-dimensional (3-D) elemental mapping of an occluded dentine is achieved with a significantly reduced data acquisition time.

Abstract There is no consensus on the involvement of zinc (Zn) dysfunctions in Parkinson’s Disease (PD). We performed a meta-analysis to evaluate whether circulating Zn levels in the serum, plasma, and cerebrospinal fluid (CSF) are altered in PD. Twenty-three published studies were selected by searching the databases of PubMed and China National Knowledge Infrastructure (CNKI). A total of 803 PD patients and 796 controls, 342 PD patients and 392 controls, and 135 PD patients and 93 controls were included to study Zn levels in the serum, plasma, and CSF, respectively. Our meta-analysis showed that the serum Zn levels were significantly lower in PD patients compared with health controls (SMD = −0.59; 95% CI [−1.06, −0.12]; P = 0.014). A reduced Zn levels in PD patients were found when serum and plasma studies were analyzed together (SMD = −0.60, 95% CI [−0.98; −0.22]; p = 0.002). PD patients had a tendency toward reduced CSF Zn levels compared with health controls (SMD = −0.50; 95% CI [−1.76, 0.76]; P = 0.439), but no statistical significance was obtained and this data did not allow conclusions due to a small sample size of CSF studies. This study suggests that reduced Zn levels in the serum and plasma are associated with an increased risk for PD.

Abstract Polymer coatings are commonly used to protect carbon steels from corrosion but they are susceptible to weathering and many of them have environmental concerns. Therefore, we studied the possibility of an environmentally favorable inorganic magnesium phosphate cement (MPC) coating for protecting mild steel. A formulation suitable for coating steel was developed by compositional modification [i.e., incremental replacement of dead-burned magnesia (MgO) with magnesium hydroxide (Mg(OH)2)] to a road-repair MPC. This modification yielded an acceptable working time and prevented pore formation at the coating-steel interface. Corrosion monitoring by linear polarization and electrochemical impedance spectroscopy for 14 days found that, the MPC coating substantially increased the linear polarization resistance (Rp) [e.g., day 1: (8.2 ± 1.7) × 103 (nadir value) vs. 495 ± 55 Ω cm−2] and charge transfer resistance (Rct) (e.g., day 1: 9.3 × 103 vs. 3.8 × 102 Ω cm−2). The coated steel underwent neutral sodium chloride (NaCl) salt spray for 2400 h without visible rusting. Immersion for 24 h in liquids simulating the pore fluid indicated that, passivation by the excess MgO in the coating was a major contributor to its anti-corrosive property. Tafel polarization in the liquids found that, corrosion current density (Icorr) followed the rank: 3.5% NaCl solution (6.0 µA cm−2) > 3.5% NaCl solution containing MgO (3.6 µA cm−2) > 3.5% NaCl solution containing fragmented MPC (1.7 µA cm−2), suggesting that a physical barrier effect and dissolved phosphate ions improved its protection. This study shows that, MPC coating is a promising durable and environmentally favorable anti-corrosive material for protecting steel structures in some applications.