Objective
To evaluate the collection efficiency of water spray on the release of airborne composite particles during grinding of composite materials.
Materials and methods
Composite sticks (L:35 mm × ...W:5.4 mm × H:1.6 mm) of seven commercial dental composites were ground with a rough diamond bur (grain size 100 μm, speed 200,000 rpm). All experiments were performed in an enclosed 1-m
3
chamber with low particulate background (< 1,000 #/cm
3
), and airborne particles were evaluated based on their electrical mobility. The number size distribution was determined by scanning mobility particle sizer (SMPS). Particles were collected by an electrostatic precipitator (ESP), and were ultramorphologically and chemically analyzed by a transmission electron microscope equipped with energy-dispersive X-ray spectroscopy (TEM-EDS).
Results
SMPS measurements confirmed that both dry and wet grinding generated high concentrations of nanoparticles particles with the highest concentration recorded during the last minute of grinding (1.80 × 10
6
− 3.29 × 10
6
#/cm
3
), after which a gradual decline in particle concentration took place. Nevertheless, grinding with water spray resulted in a significant reduction of the number of released particles (5.6 × 10
5
− 1.37 × 10
6
#/cm
3
). The smallest particle diameter was recorded during the last minute of grinding followed by a continuous growth for every next measurement. TEM of composite dust revealed a high concentration of particles varying in both size and shape.
Conclusions
Regardless of whether the water cooling spray system was used during bur manipulation of composite materials, predominately nanoparticles were released. However, the particle concentrations were significantly decreased with water spray.
Clinical relevance: Since water spray might not be sufficient in nanoparticle collection, special care should be taken to prevent inhalation of composite dust.
Third harmonic generation (THG) microscopy shows great potential for instant pathology of brain tissue during surgery. However, the rich morphologies contained and the noise associated makes image ...restoration, necessary for quantification of the THG images, challenging. Anisotropic diffusion filtering (ADF) has been recently applied to restore THG images of normal brain, but ADF is hard‐to‐code, time‐consuming and only reconstructs salient edges. This work overcomes these drawbacks by expressing ADF as a tensor regularized total variation model, which uses the Huber penalty and the L1 norm for tensor regularization and fidelity measurement, respectively. The diffusion tensor is constructed from the structure tensor of ADF yet the tensor decomposition is performed only in the non‐flat areas. The resulting model is solved by an efficient and easy‐to‐code primal‐dual algorithm. Tests on THG brain tumor images show that the proposed model has comparable denoising performance as ADF while it much better restores weak edges and it is up to 60% more time efficient.
Third harmonic generation (THG) microscopy is a label‐free imaging technique that shows great potential for in vivo instant pathology of human brain tissue. Here we have developed a robust and efficient image denoising method to facilitate the clinical applications of THG.
Abstract Objectives To evaluate the effect of mechanical and chemical surface pre-treatment on the bond durability of two composite cements to dental zirconia. Methods Fully sintered IPS e.max ZirCAD ...(Ivoclar-Vivadent) blocks were either subjected to tribochemical silica sandblasting (CoJet, 3M ESPE) or not mechanically pre-treated. Next, the zirconia samples were either additionally pre-treated using one of two silane/MDP-combined ceramic primers (Clearfil Ceramic Primer, Kuraray; Monobond Plus, Ivoclar-Vivadent), or not further chemically pre-treated. Finally, two identically pre-treated zirconia blocks were bonded together using either a conventional BisGMA-based (Clearfil Esthetic Cement, Kuraray) or an MDP-based (Panavia F2.0, Kuraray) ‘self-etch’ dual-cure composite cement. The specimens were trimmed at the interface to a cylindrical hour-glass shape and stored for 7 days in distilled water (37 °C), after which they were randomly exposed to one of three ageing protocols: (1) immersed in 37 °C water for 10 days (10 d); (2) subjected to 10,000 thermo-cycles (TC); or (3) immersed in 37 °C water for 6 months (6 m). After storage, the micro-tensile bond strength (μTBS) was determined in MPa ( n = 15–21/group). Fractographic analysis was performed using SEM. Results Weibull analysis revealed the highest Weibull scale and shape parameters for the ‘CoJet/Clearfil Ceramic Primer/Panavia F2.0/10d’ combination. While the BisGMA-based composite cement Clearfil Esthetic Cement (Kuraray) bonded equally well to zirconia using either tribochemical silica sandblasting (CoJet, 3M ESPE) or not, sandblasting appeared indispensable for the MDP-based and more hydrophilic composite cement Panavia F2.0 (Kuraray). Conclusions Combined mechanical and chemical pre-treatment can best be recommended to durably bond to zirconia. Clinical significance As a standard procedure to durable bond zirconia to tooth tissue, both mechanical (tribochemical silica coating) and chemical (silane/MDP-combined ceramic primers) is clinically highly recommended.
Objective
This study was undertaken to test the hypothesis that brain tumors interfere with normal brain function by disrupting functional connectivity of brain networks.
Methods
Functional ...connectivity was assessed by computing the synchronization likelihood in a broad band (0.5–60Hz) or in the gamma band (30–60Hz) between all pairwise combinations of magnetoencephalography signals. Magnetoencephalography recordings were made at rest in 17 brain tumor patients and 15 healthy control subjects. For a given threshold of synchronization likelihood values, graphs of the suprathreshold connections between each magnetoencephalography channel and the others channels were built.
Results
In some regions, a variable number of channels without connectivity (missing connective points) at this threshold was found. The number of missing connective points was higher in patients with brain tumors than in control subjects (p < 0.0001, broad and gamma band) and was higher for left‐sided than right‐sided tumors (p = 0.008, broad band; p < 0.0001, gamma band). Individual results analysis indicates that the majority of brain tumor patients display several regions with missing connective point alterations in the affected and in the contralateral hemisphere.
Interpretation
Our findings suggest that brain tumors induce a loss of functional connectivity that affects multiple brain regions, and that left side brain tumors have the more severe consequences in this respect. Ann Neurol 2005
Cerebral functions are based on the functional interactions between multiple distinct specialized regions of the brain. Functional interactions require anatomical connections as well as the ...synchronization of brain oscillations. The present work aims at evaluating the impact of brain tumours on spatial patterns of functional connectivity of the brain measured at rest by MEG.
We analyzed the statistical dependency (by computing the synchronization likelihood (SL, a measure of generalized synchronization)) between MEG signals at rest, in 17 patients with a brain tumour and in 15 healthy controls. Following an approach that derives from graph theory, we also analyzed the architectural properties of the networks by computing two parameters from the SL matrix, the cluster coefficient
C and the characteristic path length
L.
Alterations in synchronization levels were found in the patients and were not focal but involved intra-hemispheric connectivity. Effects were different considering the frequencies sub-bands, predominating in a decrease in high frequencies bands for long-distance connections and an increase in slower bands for local connectivity. In addition, graph analysis reveals changes in the normal “small-world” network architecture in addition to changes in synchronization levels with some differences according to the studied frequency sub-bands.
Brain tumours alter the functional connectivity and the “network” architecture of the brain. These alterations are not focal and effects are different considering the frequencies sub-bands.
These neurophysiological changes may contribute to the cognitive alterations observed in patients with brain tumours.
Co-registered EEG and functional MRI (EEG/fMRI) is a potential clinical tool for planning invasive EEG in patients with epilepsy. In addition, the analysis of EEG/fMRI data provides a fundamental ...insight into the precise physiological meaning of both fMRI and EEG data. Routine application of EEG/fMRI for localization of epileptic sources is hampered by large artefacts in the EEG, caused by switching of scanner gradients and heartbeat effects. Residuals of the ballistocardiogram (BCG) artefacts are similarly shaped as epileptic spikes, and may therefore cause false identification of spikes. In this study, new ideas and methods are presented to remove gradient artefacts and to reduce BCG artefacts of different shapes that mutually overlap in time.
Gradient artefacts can be removed efficiently by subtracting an average artefact template when the EEG sampling frequency and EEG low-pass filtering are sufficient in relation to MR gradient switching (Gonçalves et al., 2007). When this is not the case, the gradient artefacts repeat themselves at time intervals that depend on the remainder between the fMRI repetition time and the closest multiple of the EEG acquisition time. These repetitions are deterministic, but difficult to predict due to the limited precision by which these timings are known. Therefore, we propose to estimate gradient artefact repetitions using a clustering algorithm, combined with selective averaging. Clustering of the gradient artefacts yields cleaner EEG for data recorded during scanning of a 3T scanner when using a sampling frequency of 2048Hz. It even gives clean EEG when the EEG is sampled with only 256Hz.
Current BCG artefacts-reduction algorithms based on average template subtraction have the intrinsic limitation that they fail to deal properly with artefacts that overlap in time. To eliminate this constraint, the precise timings of artefact overlaps were modelled and represented in a sparse matrix. Next, the artefacts were disentangled with a least squares procedure. The relevance of this approach is illustrated by determining the BCG artefacts in a data set consisting of 29 healthy subjects recorded in a 1.5T scanner and 15 patients with epilepsy recorded in a 3T scanner. Analysis of the relationship between artefact amplitude, duration and heartbeat interval shows that in 22% (1.5T data) to 30% (3T data) of the cases BCG artefacts show an overlap. The BCG artefacts of the EEG/fMRI data recorded on the 1.5T scanner show a small negative correlation between HBI and BCG amplitude.
In conclusion, the proposed methodology provides a substantial improvement of the quality of the EEG signal without excessive computer power or additional hardware than standard EEG-compatible equipment.
► With gradient artefact clustering templates are created to correct EEG/fMRI. ► With gradient artefact clustering clean EEG can be obtained at low sampling frequency. ► BCG artefacts overlap in time 20 to 30 % of the cases. ► Overlapping BCG artefacts are effectively removed from the data.
The aim of glioblastoma surgery is to maximize the extent of resection while preserving functional integrity. Standards are lacking for surgical decision-making, and previous studies indicate ...treatment variations. These shortcomings reflect the need to evaluate larger populations from different care teams. In this study, the authors used probability maps to quantify and compare surgical decision-making throughout the brain by 12 neurosurgical teams for patients with glioblastoma.
The study included all adult patients who underwent first-time glioblastoma surgery in 2012-2013 and were treated by 1 of the 12 participating neurosurgical teams. Voxel-wise probability maps of tumor location, biopsy, and resection were constructed for each team to identify and compare patient treatment variations. Brain regions with different biopsy and resection results between teams were identified and analyzed for patient functional outcome and survival.
The study cohort consisted of 1087 patients, of whom 363 underwent a biopsy and 724 a resection. Biopsy and resection decisions were generally comparable between teams, providing benchmarks for probability maps of resections and biopsies for glioblastoma. Differences in biopsy rates were identified for the right superior frontal gyrus and indicated variation in biopsy decisions. Differences in resection rates were identified for the left superior parietal lobule, indicating variations in resection decisions.
Probability maps of glioblastoma surgery enabled capture of clinical practice decisions and indicated that teams generally agreed on which region to biopsy or to resect. However, treatment variations reflecting clinical dilemmas were observed and pinpointed by using the probability maps, which could therefore be useful for quality-of-care discussions between surgical teams for patients with glioblastoma.
Abstract Objective The functional monomer 10-MDP has been considered as one of the best performing functional monomers for dental adhesives. Different adhesives containing 10-MDP are commercially ...available, among which many so-called ‘universal’ adhesives. We hypothesize that the quality of the functional monomer 10-MDP in terms of purity may affect bonding performance. Methods We therefore characterized three different 10-MDP versions (10-MDP_KN provided by Kuraray Noritake; 10-MDP_PCM provided by PCM; 10-MDP_DMI provided by DMI) using NMR, and analyzed their ability to form 10-MDP_Ca salts on dentin using XRD. The ‘immediate’ and ‘aged’ micro-tensile bond strength (μTBS) to dentin of three experimental 10-MDP primers was measured. The resultant interfacial adhesive-dentin ultra-structure was characterized using TEM. Results NMR disclosed impurities and the presence of 10-MDP dimer in 10-MDP_PCM and 10-MDP_DMI. 10-MDP_PCM and 10-MDP_DMI appeared also sensitive to hydrolysis. 10-MDP_KN, on the contrary, contained less impurities and dimer, and did not undergo hydrolysis. XRD revealed more intense 10-MDP_Ca salt deposition on dentin induced by 10-MDP_KN. The adhesive based on the experimental 10-MDP_KN primer resulted in a significantly higher ‘immediate’ bond strength that remained stable upon aging; the μTBS of the experimental 10-MDP_PCM and 10-MDP_DMI adhesives significantly dropped upon aging. TEM revealed thicker hybridization and more intense nano-layering for 10-MDP_KN. Significance It was concluded that primer impurities and the presence of 10-MDP dimer affected not only hybridization, but also reduced the formation of 10-MDP_Ca salts and nano-layering. 10-MDP in a high purity grade is essential to achieve durable bonding.
Objectives
The aim of this study was to determine and correlate the degree of conversion (DC) with Vickers hardness (VH) and translucency parameter (TP) with the depth of cure (DoC) of five bulk-fill ...composites.
Materials and methods
Six specimens per group, consisting of Tetric EvoCeram Bulk Fill (“TEC Bulk,” Ivoclar Vivadent), SonicFill (Kerr), SDR Smart Dentin Replacement (“SDR,” Dentsply), Xenius base (“Xenius,” StickTech; commercialized as EverX Posterior, GC), Filtek Bulk Fill flowable (“Filtek Bulk,” 3M ESPE), and Tetric EvoCeram (“TEC,” control), were prepared for DC and VH: two 2-mm-thick layers, each light-cured for 10 s; one 4-mm bulk-fill, light-cured for 10 or 20 s; and one 6-mm bulk-fill, cured for 20 s. DC was measured using a Fourier-transform infrared spectrometer, VH using a Vickers hardness tester. DoC and TP were measured using an acetone-shaking test and a spectrophotometer, respectively. Data were analyzed using ANOVA and Pearson’s correlation (
α
= 0.05).
Results
DC and VH ranged between 40–70 % and 30–80 VHN, respectively. TEC Bulk, Xenius, and SonicFill, bulk-filled as 4-mm-thick specimens, showed bottom-to-top hardness ratios above 80 % after 20 s curing. A positive linear correlation was found for bottom DC and VH. An average DC ratio of 0.9 corresponded to a bottom-to-top VH ratio of 0.8.
Conclusions
Sculptable bulk-fills require 20 s, whereas 10 s curing time was sufficient for flowable bulk-fills using a high-intensity LED unit.
Clinical relevance
Clinicians should be aware that longer curing times may be required for sculptable than flowable bulk-fill composites in order to achieve optimal curing characteristics.
Electroencephalography (EEG) benefits from accurate head models. Dipole source modelling errors can be reduced from over 1cm to a few millimetres by replacing generic head geometry and conductivity ...with tailored ones. When adequate head geometry is available, electrical impedance tomography (EIT) can be used to infer the conductivities of head tissues. In this study, the boundary element method (BEM) is applied with three-compartment (scalp, skull and brain) subject-specific head models.
The optimal injection of small currents to the head with a modular EIT current injector, and voltage measurement by an EEG amplifier is first sought by simulations. The measurement with a 64-electrode EEG layout is studied with respect to three noise sources affecting EIT: background EEG, deviations from the fitting assumption of equal scalp and brain conductivities, and smooth model geometry deviations from the true head geometry. The noise source effects were investigated depending on the positioning of the injection and extraction electrode and the number of their combinations used sequentially.
The deviation from equal scalp and brain conductivities produces rather deterministic errors in the three conductivities irrespective of the current injection locations. With a realistic measurement of around 2min and around 8 distant distinct current injection pairs, the error from the other noise sources is reduced to around 10% or less in the skull conductivity. The analysis of subsequent real measurements, however, suggests that there could be subject-specific local thinnings in the skull, which could amplify the conductivity fitting errors. With proper analysis of multiplexed sinusoidal EIT current injections, the measurements on average yielded conductivities of 340mS/m (scalp and brain) and 6.6mS/m (skull) at 2Hz. From 11 to 127Hz, the conductivities increased by 1.6% (scalp and brain) and 6.7% (skull) on the average. The proper analysis was ensured by using recombination of the current injections into virtual ones, avoiding problems in location-specific skull morphology variations.
The observed large intersubject variations support the need for in vivo measurement of skull conductivity, resulting in calibrated subject-specific head models.
Display omitted
•An optimal EIT-EEG current injection strategy was sought by simulation.•The optimal strategy was implemented in measurements on nine healthy subjects.•A scalp-to-skull conductivity ratio of around 50 was found.•A skull conductivity increase of around 5% was detected from 11 to 127Hz.•The detected inter-subject variability emphasizes the use of tailored head models.
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