Search

In this study we assessed the influence of pH and time on the degradation and elution of organic substances from the composite resin material, Z-100. To accomplish this, fluorescence spectrophotometry was evaluated as an appropriate technique for the identification of six organic substances (methacrylic acid, methyl methacrylate, hydroquinone, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate and 4,4'-isopropylidenediphenol) that were eluted from resin composite material stored for 24 h or 6 months at pH 4.0, 6.0 or 8.0. In addition, complementary analyses (solid-phase microextraction/gas chromatography/mass spectrometry) were carried out to identify and quantify the substances. The main substances leached from the resin composite were methacrylic acid, triethylene glycol dimethacrylate and hydroquinone. It was concluded that fluorescence spectrophotometry seems to be a suitable, non-destructive technique for the qualitative analysis of eluted organic components. Critical combinations of time and pH allowed the elution of several organic substances, predominantly methacrylic acid, triethylene glycol dimethacrylate and hydroquinone, from the model resin composite, Z-100., (Copyright Eur J Oral Sci, 2004.)

The aim of the present study was to investigate the influence of a chemo-mechanical caries removal system, Carisolv gel, on the surface topography of dental filling materials. Thirty specimens of a composite resin (Spectrum) and a compomer (Dyract AP) and 60 specimens of a glass-ionomer (Ketac-Fil Plus) were prepared. The surface topography was investigated with an optical interferometer before and after chemical exposure for 5, 10, or 20 min. Each specimen acted as its own control. The topographical part of the glass-ionomer materials was performed in two series with different drying procedures, since this material exhibits a higher sensitivity to dehydration than the other materials. The surface topographical investigations were complemented with contact angle measurements. After Carisolv gel exposure the density of summits and the developed surface area ratio (3D/2D) were slightly smaller for the composite resin and the compomer. For the minimally dried glass-ionomer material, the results indicated a reduction of the height of the surface structures, as well as a surface area enlargement, after Carisolv gel exposure. No statistically significant changes of contact angles due to Carisolv gel exposure could be detected for any material investigated. If dental filling materials of composite resin or glass-ionomer materials are exposed to Carisolv gel, no or only minor surface topographical changes can be expected. n

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.

Objectives: The aim of this study was to determine whether pH and time has any influence on the sorption and solubility behaviour of composite resin materials stored in a buffer solution., Methods: Three hybrid composite restorative resin materials (Spectrum, Z-100 and ArtGlass) with different matrix structure and filler composition were studied. One hundred and twenty specimens of each material were produced according to ISO 4049. The materials were stored in McIlvain's buffer solution at different pH (4, 6 and 8) at 1, 7, 60 and 180 days. pH measurements were carried out before and after completed storage., Results: Time had a significant influence on the sorption and solubility behaviour of the composite resin materials tested. One of the materials Z-100 showed a significant mass increase and/or decrease depending on the pH of the solution. The material Spectrum was significantly influenced by pH, resulting in different sorption depending on the pH of the solution., Conclusions: Time of storage was important for the sorption and solubility behaviour of the composite resin materials tested. Comparison of solubility for one of the materials showed twice as high values in the present study as previously reported when distilled water was used as storage medium. pH in the solution seems to have an influence on the sorption and solubility behaviour of composite resin materials. The sensitivity of the sorption and solubility behaviour to time and pH of the materials tested seems to be related to the hydrophilicity of the matrix and the chemical composition of the filler.

Purpose: The aim of this study was to assess the water sorption and determine the influence of water on flexural properties of a composite resin cement of 2 different viscosities., Materials and Methods: A dual-cured composite resin cement of 2 different viscosities was tested according to International Standards Organization standards for dental composite materials. The samples tested for water sorption were stored in distilled water for 7 or 60 days. The samples tested for flexural properties were divided into 2 groups and stored either wet in distilled water or dry for 1, 7, or 60 days. After storage, a flexural test was performed with 3-point bending equipment., Results: A significant increase in water sorption for both viscosities was registered as the storage time increased, but no significant difference between the 2 viscosities was recorded. Significantly lower strength and modulus were found for specimens that were wet stored for 60 days compared with the dry-stored ones, and significant changes in deflection at break were also registered. There were no differences in flexural properties between the 2 viscosities. Because of the lubricant and plasticizing effect of water on composite resin materials, the secant modulus and deflection at break seem to be valid methods to describe the complete deflection behavior., Conclusion: Water has an important effect on the flexural properties of composite resin cement after 60 days of storage time. No significant differences in water sorption and flexural properties were found between the high and low viscosities of the composite resin cement studied.

Purpose: The aims of this thesis were: 1. To study the effect of water and pH on composite resin materials in vitro by assessing sorption, solubility, monomers eluted and flexural properties. 2. To study adverse effects on the skin in dentists possibly caused by acrylic resin-based materials., Materials and Methods: Proprietary composite resin materials were used for the in vitro experiments. The tests were performed according to the ISO 4049 (1988) with the exception of McIlvaine's solution used in Study II and the storage times. The analysis of eluted monomers was performed using HPLC. The flexural properties were tested in a three-point bending equipment. The secant modulus and deflection at break were calculated for description of the viscoelastic behaviour of the material tested. To study the adverse effects on skin in dentists, a questionnaire was sent to 3500 randomly selected Swedish dentists. A response rate of 88% was achieved and the data were statistically analysed and compared with the results of two studies on skin symptoms among the general Swedish population. Dentists living in the three main cities in Sweden who had experienced hand eczema during the last 12 months were invited to a clinical examination in which a patch test was included., Results: A wide range in sorption and solubility over the test period was found, with low sorption values observed for materials containing hydrophobic matrix monomers. A maximum concentration of monomers eluted was found after 7 days of storage, and TEGDMA was the main monomer released. pH affected the sorption and solubility behaviour for two of the three materials tested. The flexural strength and modulus of the composite resin material were lowered after water storage and the secant modulus and deflection at break could describe the viscoelastic behaviour. The prevalence of dry skin and hand eczema was high in dentists compared to two age-matched general population samples investigated using identical questions. The most important predictor for adult hand eczema was found to be childhood eczema. At the clinical examination, irritant contact dermatitis was the predominant diagnosis. Seven per cent reported skin symptoms when working with acrylic resin-based material but the true prevalence of hand eczema caused by acrylates was below 1%. Contact allergy was diagnosed, however, in 50% of the dentists, mainly due to other allergens such as nickel, perfumes or rubber chemicals., Conclusions: The matrix composition was shown to be important for the sorption and solubility behaviour of the composite resin materials tested and a maximum release of monomers occurred after 7 days of storage. pH affected the water sorption and solubility behaviour. Calculation of the secant modulus and the deflection at break allowed the plasticising effect of water on composite resin material to be observed. The prevalence of hand eczema was high among dentists, with irritant contact dermatitis as the predominant diagnosis. Childhood eczema was the most important predictor for adult hand eczema. The prevalence of hand eczema owing to acrylates was below 1%.

Purpose: The aims of this study were to assess changes in the microhardness and surface roughness of a dual-cured composite resin cement after water storage for different periods of time., Materials and Methods: Sixty specimens were divided into four groups comprising high- and low-viscosity cement specimens stored either dry or in water for 1 to 60 days. Microhardness and surface roughness measurements were made after 1, 7, and 60 days of storage., Results: It was found that that although interactions complicated the interpretation of the results, the water-stored samples had a significantly lower microhardness compared to the dry-stored specimens for every time interval. In addition, the high-viscosity specimens had a significantly higher microhardness compared to the low-viscosity specimens. An increased microhardness was found for all groups, except for the low-viscosity, water-stored specimens after 60 days of water storage, which was attributed to an effect of the chemical postcuring process. Although difficult to evaluate from a clinical point of view, the laser profilometry analysis revealed that a significantly increased surface roughness was found after water storage and increased storage time that was possibly caused by a deterioration of the resin-matrix surface., Conclusion: For the permanency of the interfacial luting material, a high microhardness value seems to be important.