Hygroscopic and hydrolytic effects in dental polymer networks.

Despite widespread clinical use of antimalarial drugs such as hydroxychloroquine and chloroquine in the treatment of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and other inflammatory rheumatic diseases, insights into the mechanism of action of these drugs are still emerging. Hydroxychloroquine and chloroquine are weak bases and have a characteristic ‘deep’ volume of distribution and a half-life of around 50 days. These drugs interfere with lysosomal activity and autophagy, interact with membrane stability and alter signalling pathways and transcriptional activity, which can result in inhibition of cytokine production and modulation of certain co-stimulatory molecules. These modes of action, together with the drug’s chemical properties, might explain the clinical efficacy and well-known adverse effects (such as retinopathy) of these drugs. The unknown dose–response relationships of these drugs and the lack of definitions of the minimum dose needed for clinical efficacy and what doses are toxic pose challenges to clinical practice. Further challenges include patient non-adherence and possible context-dependent variations in blood drug levels. Available mechanistic data give insights into the immunomodulatory potency of hydroxychloroquine and provide the rationale to search for more potent and/or selective inhibitors. Hydroxychloroquine and chloroquine are antimalarial drugs commonly used for the treatment of rheumatic diseases. Multiple mechanisms might explain the efficacy and adverse effects of these drugs, but further investigation could lead to the development of more specific and potent drugs.

Mechanisms of action of hydroxychloroquine and chloroquine: implications for rheumatology.

A significant amount of residual monomer or short chain polymers remain unbound in set composite material. Due to its potential impact on both the biocompatibility and the structural stability of the restoration, many investigators have studied the elution of these unbound molecules into aqueous media. The results of these studies suggest that elution of leachable components from composites is rapid, with the majority being released within a matter of hours. Weight losses of up to 2% of the mass of the composite have been reported under certain conditions. The studies have also shown that the extent and rate of elution of components from composites is dependent upon several factors. The quantity of leachables has been correlated to the degree of cure of the polymer network. The composition and solubility characteristics of the extraction solvent influence the kinetics and mechanism of the elution process. Elution is generally thought to occur via diffusion of molecules through the resin matrix, and is therefore dependent upon the size and chemical characteristics of the leachable species.

Elution of leachable components from composites.

Influence of food-simulating solutions and surface finish on susceptibility to staining of aesthetic restorative materials

Water sorption and solubility of six proprietary composite resin materials were assessed, and monomers eluted from the organic matrix during water storage identified. Water sorption and solubility tests were carried out with the following storage times: 4 h, 24 h and 7, 60 and 180 days. After storage, water sorption and solubility were determined. Eluted monomers were analysed by high performance liquid chromatography (HPLC). Correlation between the retention time of the registered peak and the reference peak was observed, and UV-spectra confirmed the identity. The results showed an increase in water sorption until equilibrium for all materials with one exception. The solubility behaviour of the composite resin materials tested revealed variations, with both mass decrease and increase. The resin composition influences the water sorption and solubility behaviour of composite resin materials. The HPLC analysis of eluted components revealed that triethyleneglycol dimethacrylate (TEGDMA) was the main monomer released. Maximal monomer concentration in the eluate was observed after 7 days. During the test period, quantifiable quantities of urethanedimethacrylate (UEDMA) monomer were observed, whereas 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane (Bis-GMA) was only found in detectable quantities. No detectable quantities of bisphenol-A were observed during the test period.

Water sorption and solubility of dental composites and identification of monomers released in an aqueous environment

The water sorption and solubility of three hybrid and one microfine composite are reported. The values obtained are dependent on composite type and resin system. Incomplete polymerization of the two materials resulted in increased solubility and sorption due to incomplete conversion of the monomer. The marked increased in both parameters will have clinical significance on the durability of the material.

Water sorption and solubility of resin-based materials following inadequate polymerization by a visible-light curing system.

The effect of acid etching on the surface appearance and flexural strength of four glass polyalkenoate cements was investigated. Specimens were etched for intervals of 10-60 s, both at the recommended time after mixing and after a 24-h delay. The surface texture was examined microscopically. Further specimens were subjected to a 4-point bend test following etching 1 h and 24 h after mixing. Deterioration of the surface appearance occurred as the etching time was increased beyond 10 s following immediate etching. Etching after 24 h reduced surface damage, but a 10-s etch still gave the most favourable surface appearance without loss of particulate material. Etching beyond 10 s significantly reduces flexural strength.

The effect of etching on glass polyalkenoate cements.

Summary

The effect of three different powder/liquid ratios of one zinc phosphate cement on the early retention of a standard crown on metal and tooth dies was investigated. Two different seating pressures were evaluated. The results indicate that the effect of variation in the powder/liquid was not significant. The part played by the seating force was significant, the higher seating force resulting in a greater force being required for displacement after 1h. Greater forces of removal were required when tooth dies were used.

The effect of seating pressure and powder/liquid ratio of zinc phosphate cement on the retention of crowns.

Summary

A previous investigation identified three types of cuspal movement that occur as a result of polymerization shrinkage when extracted molar teeth are filled with a microfine or hybrid composite used in conjunction with a dentine adhesive. That investigation was extended further by dye penetration and SEM studies of the margin, involving assessment of the degree of dye penetration and marginal integrity around the restoration. These studies indicate that there may be a failure of the adhesive bond between tooth and composite/adhesive complex which correlates with little or no cuspal movement. Failure within the tooth structure itself was also observed in a number of cases.

The effectiveness of dentine adhesives as demonstrated by dye penetration and SEM investigations

Summary

Three dental amalgams were mixed in a number of different mixing capsules. Compressive strength specimens were prepared using a clinically relevant technique and tested at 1 h and 7 days. The results showed that the early compressive strength of an alloy was influenced by the mixing capsule, and suggested that internal capsule geometry may be an important contributary factor in capsule performance. With one exception, there was a marked difference between the compressive strengths produced under the present method and those reported by manufacturers under test conditions laid down in standards specifications.

The effects of mixing capsule geometry on the early compressive strength of dental amalgam.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

G. J. Pearson

Author Tools

Chat about Author