Effect of layer thickness on the elution of bulk-fill composite components

Objective

An increment layering technique in a thickness of 2 mm or less has been the standard to sufficiently convert (co)monomers. Bulk fill resin composites were developed to accelerate the restoration process by enabling up to 4 mm thick increments to be cured in a single step. The aim of the present study is to investigate the effect of layer thickness on the elution of components from bulk fill composites.

Safety assessment of jumps in ski racing

The influence of important parameters on the flight trajectory for jumps in downhill World Cup races was investigated. To quantify the impact injury risk at landing, the parameter equivalent landing height (ELH) was introduced, which considered a variable slope inclination during the landing movement. Altogether, 145 runs at four different jumps in World Cup races and trainings were recorded and analyzed. A simulation model was developed to predict the flight phase of the skier. Drag and lift areas were selected by parameter identification to fit the simulation trajectory to the two‐dimensional data from the video analysis. The maximum values of the ELH which can be absorbed with muscle force was taken from the study of Minetti et al. for elite female and male ski racers. A sensitivity analysis based on the four jumps showed that ELH is mainly influenced by takeoff angle, takeoff speed, and the steepness of the landing surface. With the help of the developed simulation software, it should be possible to predict the ELH for jumps in advance. In case of an excessive ELH, improvements can be made by changing the takeoff inclination or the approach speed.     

Corticosteroids: way upstream

Background

In recent years, several lines of evidence have shown an increase in Parkinson's disease prevalence in rural environments where pesticides are heavily used. Although, the underlying mechanism for neuronal degeneration in sporadic PD remains unknown, mitochondrial dysfunction, oxidative stress and proteasomal dysfunction are proposed as contributing factors. In this study rats were chronically and continuously exposed to the pesticide, dichlorvos to identify the molecular mechanism of nigrostaital neuronal degeneration.

Result

Chronic dichlorvos exposure (2.50 mg/kg b.wt.s.c/daily for 12 weeks) caused nigrostriatal dopaminergic degeneration. The degenerative changes were accompanied by a loss of 60-80% of the nigral dopamine neurons and 60-70% reduction in striatal dopamine and tyrosine hydroxylase levels. Dichlorvos exposed animals also showed α -synuclein and ubiquitin positive inclusions along with swollen, dystrophic neurites and mitochondrial abnormalities like decreased complex I&IV activities, increased mitochondrial size, axonal degeneration and presence of electron dense perinuclear cytoplasmic inclusions in the substantia nigra of rats. These animals also showed evidence of oxidative stress, including increased mitochondrial ROS levels, decreased MnSOD activity and increased lipid peroxidation. Measurable impairments in neurobehavioral indices were also observed. Notable exacerbations in motor impairments, open field and catalepsy were also evident in dichlorvos exposed animals.

Conclusion

All these findings taken together indicate that chronic dichlorvos exposure may cause nigrostaital neurodegenaration and significant behavioral impairments.     

Mercuric dichloride induces DNA damage in human salivary gland tissue cells and lymphocytes

Amalgam is still one of the most frequently used dental filling materials. However, the possible adverse effects especially that of the mercuric component have led to continued controversy. Considering that mercury may be released from amalgam fillings into the oral cavity and also reach the circulating blood after absorption and resorption, it eventually may contribute to tumorigenesis in a variety of target cells. The present investigation focuses on genotoxic effects below a cytotoxic dose level of mercuric dichloride (HgCl₂) in human samples of salivary glands and lymphocytes to elucidate a possible role in tumor initiation. DNA migration due to single strand breaks, alkali labile sites and incomplete excision repair was quantified with the aid of the single cell microgel electrophoresis (Comet) assay. The concepts of Olive Tail Moment, percentage of DNA in the Tail and Tail Length were used as measures of DNA damage. To control for cytotoxic effects, the trypan blue exclusion test was applied. Human samples of the parotid salivary gland and lymphocytes of ten donors were exposed to HgCl₂ concentrations from 1 to 50 μM. N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) served as controls. Increasing dose-dependent DNA migration could be demonstrated after exposure to HgCl₂ in cells of the salivary glands and lymphocytes. In both cell types a significant increase in DNA migration could be shown starting from HgCl₂ concentrations of 5 μM in comparison to the negative control. The viability of the cell systems was not affected except at the highest concentration (50 μM) tested. These data indicate genotoxic effects of mercuric dichloride in human salivary glands and lymphocytes at concentrations not leading to cytotoxic effects or cell death. Consequently, a contributory role in oral salivary gland tumor initiation warrants further investigation. The authors declare that there is no conflict of interest.     

New avian suspension cell lines provide production of influenza virus and MVA in serum-free media: Studies on growth,metabolism and virus propagation

Few suspension cells can be used for vaccine manufacturing today as they either do not meet requirements from health regulatory authorities or do not produce high virus titres. Two new avian designer cell lines (AGE1.CR and AGE1.CR.pIX) that have been adapted to grow in suspension in serum-free medium were evaluated for their potential as host cells for influenza and modified vaccinia Ankara (MVA, wild type) vaccine production. Their metabolism was studied during growth in static (T-flasks) and dynamic cultivation systems (roller bottles, stirred tank reactor, wave bioreactor). High cell concentrations up to 5.8 × 10⁶ cells/mL were obtained with doubling times of 23 h for AGE1.CR and 35 h for AGE1.CR.pIX, respectively. Both viruses were produced to high titres (3.5 log HA/100 μL for influenza virus, 3.2 × 10⁸ pfu/mL for MVA). Hence, the CR cell lines are an appropriate substrate for pharmaceutical influenza and MVA production.     

Inhibition of cytokine and surface antigen expression in LPS-stimulated murine macrophages by triethylene glycol dimethacrylate

Dental resin monomers like triethylene glycol dimethacrylate (TEGDMA) cause a shift in the cellular redox balance which influences redox-sensitive signaling pathways. The immediate response of the innate immune system to inflammatory challenges is controlled by related pathways. Therefore, the influence of TEGDMA on the expression of the pro- and anti-inflammatory cytokines TNF-α, IL-6, and IL-10 and surface antigens (CD14, CD40, CD80, CD86, CD54, MHC class I and II) was analyzed in RAW264.7 macrophages. No significant change in cytokine production or surface antigen expression was detected after the macrophages were treated with increasing TEGDMA concentrations for 6, 24, and 48 h. However, co-stimulation with the bacterial endotoxin lipopolysaccharide (LPS) and TEGDMA resulted in a concentration-dependent inhibition of LPS-induced release of TNF-α, IL-6, and IL-10 by about 90% as detected by ELISA. Flow-cytometric analyses indicated an LPS-stimulated expression of all surface antigens. The LPS-induced expression of CD14 was inhibited by high TEGDMA concentrations. CD40 and CD80 expressions were down-regulated by TEGDMA in LPS-stimulated cells, and CD86 as well as MHC class I expression was inhibited to a lesser extent. The LPS-stimulated expression of CD54 (ICAM-1) was increased about twofold by increasing TEGDMA concentrations after a 24 and 48 h exposure. Thus, the ability of macrophages to induce an appropriate immune response is inhibited by TEGDMA which reduces cytokine production and expression of surface antigens.     

Specific hygiene issues relating to reprocessing and reuse of single-use devices for laparoscopic surgery

OBJECTIVE: To determine whether reprocessed single-use devices (SUD) would (1) meet regulatory standards for sterility, and (2) meet the same material standards as new devices or if they pose an infection risk to other patients. DESIGN: The study included in the first stage single-use laparoscopic dissection devices and in the second stage a variety of clinically used and reprocessed SUDs. The suitability of these devices for cleaning, disinfection, and sterilization was examined. METHODS: Testing of cleanability was conducted on devices contaminated with radioactively labeled blood. Instruments were cleaned using hospital recommended practices. Gamma counts/second were determined before and after cleaning to localize contaminants, which were additionally visualized using light and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to quantify contamination elements on the materials tested. Residual bioburden testing on instruments contaminated with microorganisms suspended in blood prior to reprocessing was carried out to establish the efficacy of disinfection and sterilization. RESULTS: During the first stage of the study all devices remained contaminated after cleaning, but were effectively disinfected. Sterilization could not eliminate the challenge microorganisms completely. The findings during the second stage--examination of clinically used devices--were as follows: 11% of the sterile packages were damaged; 33% of the devices were incomplete and parts were missing; 54% did not meet the criteria for functionality; light microscopy, SEM, and XPS showed contamination on the outside and inside of all devices. Of the tested SUDs, 40% remained unsterile following resterilization.CONCLUSIONS: None of the reprocessed SUDs were effectively cleaned or sterilized. This may provide an opportunity for survival and growth of non-resistant or nosocomial organisms and viruses. The use of such inadequately reprocessed SUDs increases the risk for the patient, and can lead to nosocomial infection and to legal consequences for the health care facility.     

Microbiological, microstructure, and material science examinations of reprocessed Combitubes after multiple reuse

Reprocessing (repeated cleaning, disinfection, and sterilization) and reuse of single-use medical devices has been performed safely with some devices. The aim of our study was to analyze whether reprocessing of the Combitubes (Kendall-Sheridan, Argyll, NY) airway device, used for emergency endotracheal intubation and difficult airway management, is possible and can be performed appropriately and safely. Microbiological, microstructure, and material science examinations were performed with unused, as well as multiple reused and reprocessed Combitubes. The reprocessing procedure consisted of a cleaning, a disinfection, a final inspection, and a sterilization. Microbiological examinations of multiple reused and reprocessed Combitubes found no test organisms in quantitative cultures. A microbial reduction between four and five log levels compared with nonreprocessed tubes was found. Microstructure analysis for the examination of topographical alterations and changes in the chemical composition of the surface demonstrated nonsignificant alterations between new and reprocessed medical devices. In material science examinations, cuff burst pressures were not different between unused and multiple reprocessed Combitubes. The results of all examinations proved that the decontamination process is adequately effective, and that no significant superficial alterations are generated by the multiple reuse and reprocessing of the Combitubes. To assure uniformly good results, a quality management system must be established and only validated methods should be used. IMPLICATIONS: Reprocessing of single-use medical devices offers the opportunity of significant savings and is already performed with some devices. Microbiological, microstructure, and material science examinations proved that reprocessing of multiple reused Combitubes (Kendall-Sheridan, Argyll, NY), mainly used for emergency airway management, is possible and safe.     

Cytotoxicity and induction of DNA double-strand breaks by components leached from dental composites in primary human gingival fibroblasts

Introduction

The public interest steadily increases in the biological adverse effects caused by components released from resin-based dental restorations.

Objective

In this study, the cytotoxicity and the genotoxicity were investigated of following released components from dental resin restorations in human gingival fibroblasts (HGF): tetraethyleneglycol dimethacrylate (TEEGDMA), neopentylglycol dimethacrylate (Neopen), diphenyliodoniumchloride (DPIC), triphenyl-stibane (TPSB) and triphenylphosphane (TPP).

Methods

XTT based cell viability assay was used for cytotoxicity screening of substances. γ-H2AX assay was used for genotoxicity screening. In the γ-H2AX assay, HGFs were exposed to the substances for 6 h. Induced foci represent double DNA strand breaks (DSBs), which can induce ATM-dependent phosphorylation of the histone H₂AX. Cell death effects (apoptosis and necrosis), induced by the substances were visually tested by the same investigator using the fluorescent microscope.

Results

All tested substances induced a dose-dependent loss of viability in HGFs. Following toxicity ranking among the substances at EC₅₀-concentration were found in the XTT assay (mM, mean ± SEM; n = 5): DPIC > Neopen > TPSB > TPP > TEEGDMA.DSB-foci per HGF-cell were obtained, when HGFs were exposed to the EC₅₀-concentration of each substance in the following order (mean ± SEM; n = 3): DPIC > Neopen > TPSB > TPP > TEEGDMA.Multi-foci cells (cells that contain more than 40 foci each) in 80 HGF-cells at EC₅₀-concentration of each substance were found as follow (mean ± SEM; n = 3): DPIC > Neopen > TPP > TPSB > TEEGDMA.Cell apoptosis contained in each substance at EC₅₀-concentration in the following order (mean ± SEM; n = 3): DPIC > Neopen > TPSB > TPP >TEEGDMA. Cell necrosis contained in each substance at EC₅₀-concentration in the following order (mean ± SEM; n = 3): DPIC > Neopen > TPSB > TPP > TEEGDMA.

Conclusion

Leached components from dental resin restorations can induce DNA DSBs and cell death effects in HGFs.