Effect of dimethyl sulfoxide on dentin collagen

Objectives. Infiltration of adhesive on dentin matrix depends on interaction of surface and adhesive. Interaction depends on dentin wettability, which can be enhanced either by increasing dentin surface energy or lowering the surface energy of adhesive. The objective was to examine the effect of dimethyl sulfoxide (DMSO) on demineralized dentin wettability and dentin organic matrix expansion. Methods. Acid-etched human dentin was used for sessile drop contact angle measurement to test surface wetting on 1-5% DMSO-treated demineralized dentin surface, and linear variable differential transformer (LVDT) to measure expansion/shrinkage of dentinal matrix. DMSO-water binary liquids were examined for surface tension changes through concentrations from 0 to 100% DMSO. Kruskal-Wallis and Mann-Whitney tests were used to test the differences in dentin wettability, expansion and shrinkage, and Spearman test to test the correlation between DMSO concentration and water surface tension. The level of significance was p 80%) DMSO concentrations which expanded demineralized dentin more than water. Drying times of LVDT samples increased significantly with the use of DMSO. Significance. Increased dentin wettability may explain the previously demonstrated increase in adhesive penetration with DMSO-treated dentin, and together with the expansion of collagen matrix after drying may also explain previously observed increase in dentin adhesive bonding. (C) 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.Peer reviewe

Cytotoxicity of dental composites and other materials in a new in vitro device

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73901/1/j.1600-0714.1988.tb01304.x.pd

The Influence Of Tubule Density And Area Of Solid Dentin On Bond Strength Of Two Adhesive Systems To Dentin.

To determine the correlation between the tubule density (TD) and the area occupied by solid dentin (ASD) with the bond strength of one conventional and one self-etching adhesive system to dentin. The crown of extracted human third molars was transversally sectioned with a diamond saw to expose either superficial, middle, or deep dentin. The three groups of dentin surfaces were randomly divided and bonded with either Clearfil Liner Bond 2V (LB) or Prime & Bond 2.1 (PB) adhesive systems according to manufacturer's directions. Resin composite buildup crowns (10.0 mm high) were incrementally constructed on the bonded surfaces and the teeth stored in water at 37 degrees C. After 24 h of storage, the teeth were vertically, serially sectioned in both x and y directions to obtain several bonded sticks of approximately 0.7 mm2 cross-sectional area. Each stick was tested in tension in a EMIC DL-500 tester at 0.5 mm/min until failure. After testing, the dentin side of the fractured specimen was gently abraded with a 1000-grit SiC paper, etched with 37% phosphoric acid for 15 s and allowed to air dry. SEM micrographs at 1000x and 4000x magnification were taken to permit calculation of the TD (number of tubules/mm2) and ASD (% of total area) at the site of fracture. Correlation between TD and ASD with the bond strength data was performed by linear regression. All statistical analysis was done with alpha = 0.05. Overall bond strength (MPa) for LB was 26.0 +/- 10.2, and 42.6 +/- 15.2 for PB. There was a significant direct relationship between bond strength and ASD for both materials (r2 = 0.20, p 0.05). Mean bond strength of PB was significantly higher than LB for both superficial and middle dentin (p 0.05). Regional variations in TD and ASD may modify bond strength of both conventional and self-etching adhesive systems. Bonding sites with larger ASD seem to yield higher bond strengths regardless of the type of adhesive system used.3315-2

Characterization of the “in vitro pulp chamber” using the cytotoxicity of phenol

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71980/1/j.1600-0714.1989.tb00744.x.pd

Optimisation of a current generation ICP-QMS and benchmarking against MC-ICP-MS spectrometry for the determination of lead isotope ratios in environmental samples

© 2018 The Royal Society of Chemistry. Novel ANOVA methodology was used to benchmark ICP-QMS against MC-ICP-MS for Pb isotope ratios, demonstrating "fitness-for-purpose" in environmental source apportionment. The precision and accuracy of lead (Pb) isotope measurements obtained from quadrupole-based mass spectrometers (ICP-QMS) are considered to be limited by a number of factors originating in different components of the instruments. In this study, experimental and instrumental protocols were optimised for determining lead isotope ratios in urban soil digests. Experimental measures included individual dilution of all samples and isotopic standards (SRM-981, NIST) to a single Pb concentration intended to produce an intensity which was high enough to negate blanks and interferences but low enough to ensure the detector operated only in pulse counting mode. Instrumental protocols included batch dead time correction, optimisation of dwell time and the number of scans employed and correction of mass discrimination by sequential application of both internal ( 203 Tl/ 205 Tl ratio) and external (SRM-981, NIST) standards. This optimised methodology was benchmarked against multi-collector mass spectrometer (MC-ICP-MS) measurements of Pb isotope ratios using replicate digest solutions of the same soil; but after these had been subjected to Pb separation using an ion-exchange procedure. On the assumption that MC-ICP-MS measurements are more accurate, small additive and multiplicative differences were observed in only the 4 th decimal place. ANOVA was used to compare the precisions of the two techniques demonstrating equal precisions c. 0.08% for 207 Pb/ 206 Pb, suggesting a sample heterogeneity limitation. By contrast, for 207 Pb/ 204 Pb, the worst-case ratio, ICP-QMS had a 10-fold poorer precision, despite negligible interference from 204 Hg, implying an instrumental limitation. The study concludes that ICP-QMS can provide valuable source apportionment information for most Pb isotope ratios but further efforts should focus on improving assay of the 207 Pb/ 204 Pb ratio

A new type of reconstruction on the InSb() surface determined by grazing incidence X-ray diffraction

The (3×3) reconstruction of the InSb( ) surface has been investigated by grazing incidence X-ray diffraction and scanning tunneling microscopy. The structure is characterized by 6-atom rings on top of a slightly buckled InSb top double layer. Two types of rings have been found, an elliptic ring consisting of 4 In and 2 Sb atoms and a trigonal ring with 3 In and 3 Sb atoms. The bond angles and lengths are consistent with the concept of rehybridization and depolarization which explains the reconstructions of the (111) and (110) surfaces

Substantivity of Carbodiimide Inhibition on Dentinal Enzyme Activity over Time

The use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC) has recently been investigated for its effectiveness in the prevention of collagen degradation over time and the improvement of resin-dentin bond durability. The objective of the present study was to evaluate the effects of a 0.3 M EDC-containing conditioner on endogenous enzymatic activities within the hybrid layer (HL) created by a self-etch or an etch-and-rinse adhesive after 1 y. The activity within the HL was examined using in situ zymography and confocal laser scanning microscopy after 24 h or 1-y storage in artificial saliva. Dentin specimens were bonded with Clearfil SE Bond (CSE) or XP Bond (XPB). For CSE, the self-etching primer was applied and treated with 0.3 M EDC for 1 min, and then the bonding agent was applied. For XPB, dentin was etched and treated with 0.3 M EDC for 1 min and then bonded with the primer-bonding agent. Control specimens were prepared without EDC treatment. Slices containing the adhesive-dentin interface were covered with fluorescein-conjugated gelatin and observed with a multiphoton confocal microscope. Fluorescence intensity emitted by hydrolyzed fluorescein-conjugated gelatin was quantified, and the amount of gelatinolytic activity was represented by the percentage of green fluorescence emitted within the HL. After 24 h of storage, enzymatic activity was detected by in situ zymography within the HLs of both tested adhesives, with XPB higher than CSE (P <0.05). Almost no fluorescence signal was detected when specimens were pretreated with EDC compared to controls (P <0.05). After 1 y of storage, enzymatic activities significantly increased for all groups (excluding XPB control) compared to 24-h storage (P <0.05), with EDC pretreated specimens exhibiting significantly lower activity than controls (P <0.05). The present study showed, for the first time, that the use of EDC for both the self-etch and the etch-and-rinse approaches results in the reduction but not complete inhibition of matrix-bound collagenolytic enzyme activities over time in the HL.Peer reviewe

A lattice gas model of II-VI(001) semiconductor surfaces

We introduce an anisotropic two-dimensional lattice gas model of metal terminated II-IV(001) seminconductor surfaces. Important properties of this class of materials are represented by effective NN and NNN interactions, which result in the competition of two vacancy structures on the surface. We demonstrate that the experimentally observed c(2x2)-(2x1) transition of the CdTe(001) surface can be understood as a phase transition in thermal equilbrium. The model is studied by means of transfer matrix and Monte Carlo techniques. The analysis shows that the small energy difference of the competing reconstructions determines to a large extent the nature of the different phases. Possible implications for further experimental research are discussed.Comment: 7 pages, 2 figure

Hydration interactions: aqueous solvent effects in electric double layers

A model for ionic solutions with an attractive short-range pair interaction between the ions is presented. The short-range interaction is accounted for by adding a quadratic non-local term to the Poisson-Boltzmann free energy. The model is used to study solvent effects in a planar electric double layer. The counter-ion density is found to increase near the charged surface, as compared with the Poisson-Boltzmann theory, and to decrease at larger distances. The ion density profile is studied analytically in the case where the ion distribution near the plate is dominated only by counter-ions. Further away from the plate the density distribution can be described using a Poisson-Boltzmann theory with an effective surface charge that is smaller than the actual one.Comment: 11 Figures in 13 files + LaTex file. 20 pages. Accepted to Phys. Rev. E. Corrected typos and reference

Unintentional high density p-type modulation doping of a GaAs/AlAs core-multi-shell nanowire

Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of considerable technological importance but remains a challenge due to the amphoteric behavior of the dopant atoms. Here we show that placing a narrow GaAs quantum well in the AlAs shell effectively getters residual carbon acceptors leading to an \emph{unintentional} p-type doping. Magneto-optical studies of such a GaAs/AlAs core multi-shell NW reveal quantum confined emission. Theoretical calculations of NW electronic structure confirm quantum confinement of carriers at the core/shell interface due to the presence of ionized carbon acceptors in the 1~nm GaAs layer in the shell. Micro-photoluminescence in high magnetic field shows a clear signature of avoided crossings of the $n=0$ Landau level emission line with the $n=2$ Landau level TO phonon replica. The coupling is caused by the resonant hole-phonon interaction, which points to a large 2D hole density in the structure.Comment: just published in Nano Letters (http://pubs.acs.org/doi/full/10.1021/nl500818k