In vitro cytotoxicity of a remineralizing resin-based calcium phosphate cement.

Recently, a resin-based calcium phosphate cement (RCPC) has been reported as a remineralizing pulp-capping or lining cement. RCPC consists mainly of tetracalcium and dicalcium phosphates, ethoxylated bisphenol A dimethacrylate and pyromellitic glycerol dimethacrylate monomers and photo- and chemical initiators. OBJECTIVES: Here, the cytotoxic effects of RCPC were evaluated. The hypothesis was that RCPC induced only minor cytotoxic response in immortalized murine odontoblast and pulp cells, comparable to that produced by similar dimethacrylates due to unpolymerized dimethacrylate monomer present after curing. METHODS: Cytotoxicity was determined following the changes in cell succinate dehydrogenase activity after 24 h exposure to the cement components and after a 24 h recovery period. A fourfold range of concentrations was tested of the monomers, the eluate of cured RCPC leached in Dulbecco's modified Eagle's medium, and crushed cured cement in dimethyl sulfoxide. RESULTS: The monomers themselves had cytotoxicities similar to those reported for other dimethacrylates, although they are significantly less toxic than Bis-GMA. Differential cell sensitivity was demonstrated, with the pulp cells having greater sensitivity to the unpolymerized monomer than the odontoblast-like cells. The leached components have cytotoxicity similar to that of the free monomers. The crushed material demonstrated no apparent cytotoxicity at the dilutions tested. SIGNIFICANCE: These data demonstrate that RCPC has an in vitro cytotoxicity that is comparable to other materials containing dimethacrylate monomers and suggest that the material may be suitable for use in dental restorations. The data also indicate that the pulp cells appear more sensitive to dimethacrylates than the odontoblasts.     

An alternate methodology for studying diffusion and elution kinetics of dimethacrylate monomers through dentinal tubules

ObjectiveEthoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only.MethodsIn 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates.ResultsbisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h.SignificanceDepending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.     

First multi-target QSAR model for predicting the cytotoxicity of acrylic acid-based dental monomers

ObjectiveAcrylic acid derivatives are frequently used as dental monomers and their cytotoxicity towards various cell lines is well documented. This study aims to probe the structural and physicochemical attributes responsible for higher toxicity of dental monomers, using quantitative structure-activity relationships (QSAR) modeling approaches.MethodsA regression-based linear single-target QSAR (st-QSAR) model was developed with a comparatively small dataset containing 39 compounds, the cytotoxicity of which has been assessed over the Hela S3 cell line. By contrast, a classification-based multi-target QSAR model was developed with 138 compounds, the cytotoxicity of which has been reported against 18 different cell lines. Both models were set up following rigorous validation protocols confirming their statistical significance and robustness.ResultsThe performance of the linear mt-QSAR model, developed with various feature selection and post-selection similarity searching-based schemes, superseded that of all non-linear models produced with six machine learning methods by hyperparameter optimization. The final derived st-QSAR and mt-QSAR linear models are shown to be highly predictive, as well as revealing the crucial structural and physicochemical factors responsible for higher cytotoxicity of the dental monomers.SignificanceThis study is the first attempt on unveiling the cytotoxicity of dental monomers over several cell lines by means of a single multi-target QSAR model. Further, such a model is ready to get widespread applicability in the screening of new monomers, judging from its almost accurate predictions over diverse experimental assay conditions.     

Analysis of polymerization behavior of dental dimethacrylate monomers by differential scanning calorimetry

The polymerization and copolymerization activity of dental monomers was investigated using the dynamic differential scanning calorimetry (DSC) method. As aliphatic dimethacrylate monomers, ethyleneglycol dimethacrylates with different lengths of ethyleneglycol and urethane dimethacrylates were used. As aromatic dimethacrylates, Bis-GMA (2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane), BMPEPP (2,2-bis(4-methacryloxy poly-ethoxyphenyl)propane), and DMB (1,2-dimethacryloyloxy benzene) were used. Ethyleneglycol dimethacrylates showed sharp exothermic peaks, and the maximum temperatures (Tp) at the exothermic peaks of the DSC curves decreased according to the lengths of ethyleneglycols. Among urethane dimethacrylates, UDMA (dimethacryloxyethyl 2,2,4-trimethylhexamethylene diurethane) and DMPHU (di-(2-methacryloxypropyl) hexamethylene diurethane) showed sharp exothermic peaks, but DMEHU (di-(2-methacryloxyethyl) hexamethylene diurethane) showed an endothermic peak as well as exothermic peaks. This suggests that reactions other than polymerization occurred in the case of DMEHU. The polymerization activity of aromatic dimethacrylates was lower than that of ethyleneglycol dimethacrylates and urethane dimethacrylates. The copolymerization activity of TEGDMA (triethyleneglycol dimethacrylate) and DMB was also investigated using the dynamic DSC method. The DSC curves of the copolymerization between DMB and UDMA or BMPEPP showed broad peaks, but the DSC curves of the copolymerization between TEGDMA and UDMA or BMPEPP showed sharp peaks. The copolymerization activity of TEGDMA was better than that of DMB.     

Detection and quantification of monomers in unstimulated whole saliva after treatment with resin-based composite fillings in vivo

Resin-based dental restorative materials contain allergenic methacrylate monomers, which may be released into saliva after restorative treatment. Monomers from resin-based composite materials have been demonstrated in saliva in vitro; however, studies analyzing saliva after restorative therapy are scarce. The aim of this study was to quantify methacrylate monomers in saliva after treatment with a resin-based composite filling material. Saliva was collected from 10 patients at four start points--before treatment, and 10 min, 24 h, and 7 d after treatment--and analysed by combined chromatography/mass spectrometry. The monomers bisphenol-A diglycidyl methacrylate (Bis-GMA), 2-hydroxyethyl methacrylate (HEMA), and urethane dimethacrylate (UDMA) were detected and quantified in the samples collected shortly (10 min) after treatment. The amounts detected ranged from 0.028 to 9.65 μg ml(-1) for Bis-GMA, from 0.015 to 0.19 μg ml(-1) for HEMA, and from 0.004 to 1.2 μg ml(-1) for UDMA. Triethyleneglycol dimethacrylate (TEGDMA) was detected in four of the samples. Ethoxylated bisphenol-A dimethacrylate (Bis-EMA) was not detected. Monomers were not detected in saliva samples collected before treatment, or 24 h or 7 d after treatment, with the exception of one sample, 24 h after treatment, in which HEMA was detected. In conclusion, monomers from the investigated resin-based composite and adhesive system were present in saliva shortly after treatment. One week after treatment, no monomers could be detected in patients' saliva samples.     

The in vitro cytotoxicity of eluates from dentin bonding resins and their effect on tyrosine phosphorylation of L929 cells.

OBJECTIVES: The aim of this study was to examine the relationship between the monomers eluted from dentin-bonding systems and their cytotoxicities, and to investigate the biochemical effect of the monomers on tyrosine phosphorylation, especially relating to the cell growth activity, of L929 cells in vitro. METHODS: The primers, uncured or cured adhesives (3M and Kuraray) were tested to determine the cytotoxicity of confluent L929 cells cultured by Eagle's MEM medium supplemented with 10% FCS. The area of cells affected by the eluted monomers were evaluated with an image analyzer and the concentrations of monomers eluted into the medium were measured with high performance liquid chromatography (HPLC) after 24h incubation. The protein composition of the stimulated cells was compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tyrosine phosphorylation was detected by Western blot. RESULTS: The primer and uncured adhesives revealed variable cytotoxicities. 2-hydroxyethyl-methacrylate (HEMA) was the major component eluted from uncured primers and adhesives. Small amounts of triethylene glycol dimethacrylate (TEGDMA) were also detected from the uncured adhesives. The cytotoxicities of the adhesives decreased as photo activation time increased. The amount of monomers eluted from the cured adhesives was almost undetectable and did not reach a sufficient concentration to suppress cell viability or cell growth. The cytotoxicities of the primers and adhesives correlated well with the amounts of either HEMA or TEGDMA eluted. Moreover, a high concentration of HEMA (4 mg/ml medium) affected intracellular tyrosine phosphorylation, which is related to cellular activities. SIGNIFICANCE: Although the monomers present in dentin bonding resins are cytotoxic to L929 cells, the amount from cured bonding resin is very small and does not provide a cytotoxic dose. This data does however suggest that clinical exposure to the uncured primers and adhesives of dentin bonding resins should be minimized.     

Synthesis and characterization of acetyloxypropylene dimethacrylate as a new dental monomer

Objective

In this study acetyloxypropylene dimethacrylate was synthesized and proposed as an alternative monomer for triethyleneglycol dimethacrylate (TEGDMA) in dental mixtures.

Methods

The monomer was prepared by the reaction of glycerol dimethacrylate with acetic anhydride. The exchange reaction was carried out in the presence of catalytic amounts of sulfuric acid. After purification the monomer was mixed with 2,2-dimethoxy-2-phenyloacetophenone and photo-irradiated. Unfilled homopolymer was evaluated for photopolymerization conversion and volumetric curing shrinkage. Water sorption, water solubility, flexural strength and hardness were measured. Also, dynamic mechanical studies were performed. For comparison TEGDMA was homopolymerized and its properties were evaluated.

Results

The proposed dimethacrylate has viscosity comparable to TEGDMA, lower curing shrinkage and lower degree of double bond conversion. After homopolymerization, its water sorption is much lower than that of homopolymerized TEGDMA. Concerning the mechanical properties, the homopolymerized acetyloxypropylene dimethacrylate has higher modulus and hardness than analogically cured TEGDMA.

Significance

New dimethacrylate is a promising photocurable dental diluent owing to its low viscosity, good mechanical and water uptake properties.     

Alterations of energy metabolism and glutathione levels of HL-60 cells induced by methacrylates present in composite resins

OBJECTIVES: Methacrylic compounds such as 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA) and bisphenol A glycerolate (1 glycerol/phenol) dimethacrylate (Bis-GMA) are largely present in auto- or photopolymerizable composite resins. Since the polymerization reaction is never complete, these molecules are released into the oral cavity tissues and biological fluids where they could cause local adverse effects. The aim of this work was to verify the hypothesis that the biological effects of HEMA, TEGDMA and Bis-GMA - at a non-cytotoxic concentration - depend on the interaction with mitochondria and exert consequent alterations of energy metabolism, GSH levels and the related pathways in human promyelocytic cell line (HL-60). METHODS: The biological effects of methacrylic monomers were determined by analyzing the following parameters: GSH concentration, glucose-6-phosphate dehydrogenase (G6PDH) and glutathione reductase (GR) activity, oxygen and glucose consumption and lactate production along with cell differentiation and proliferation. RESULTS: All monomers induced both cellular differentiation and decrease in oxygen consumption. Cells treated with TEGDMA and Bis-GMA showed a significant enhancement of glucose consumption and lactate production. TEGDMA and HEMA induced GSH depletion stimulating G6PDH and GR activity. CONCLUSIONS: All the monomers under study affect the metabolism of HL-60 cells and show differentiating activity. Since alterations in cellular metabolism occurred at compound concentrations well below cytotoxic levels, the changes in energy metabolism and glutathione redox balance could be considered as potential mechanisms for inducing clinical and sub-clinical adverse effects and thus providing useful parameters when testing biocompatibility of dental materials.     

Structure–property relationships in dimethacrylate networks based on Bis-GMA,UDMA and TEGDMA

ObjectivesIn this work the influence of structural heterogeneity of poly(dimethacrylate)s on mechanical properties was investigated. Rigid aromatic dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and flexible aliphatic urethane dimethacrylate (UDMA) have been chosen for room-temperature homopolymerizations and copolymerizations induced by a camphorquinone/N,N-dimethylaminoethyl methacrylate photoinitiating system.MethodsThe following mechanical properties of poly(dimethacrylate)s were investigated: flexural modulus, flexural strength, impact strength and hardness. Atomic force microscopy (AFM) and X-ray powder diffraction (XRPD) were used to describe the morphology of polymer networks.ResultsAFM observations showed that the heterogeneity of networks is spatially organized due to the formation of microgels and their agglomeration. Observed agglomerates are unidirectionally oriented, parallel to the direction of polymerization shrinkage. Of all the investigated mechanical properties of poly(dimethacrylate)s, the impact resistance appeared to be the least. The origin of this brittleness could be the presence of heterogeneities which were quantitatively characterized by means of XRPD. The impact resistance was shown to be related to the size of network heterogeneities which is probably influenced by intermolecular interactions, such as hydrogen bonding.SignificanceDifferences in monomer structure resulted in significantly different morphology and physical properties of the polymer networks which had been studied. The size and shape of heterogeneities affected the final mechanical properties of the polymers, especially impact resistance. In addition, the combined application of XRPD and AFM techniques can be a successful tool in the analysis of the dimethacrylate network morphology, and finally, in investigations on methacrylate-based dental materials.     

Detection of bisphenol-A in dental materials by gas chromatography-mass spectrometry

The xenoestrogenic substance bisphenol-A is widely used as a synthetic precursor of resin monomers, such as bisphenol-A diglycidyl methacrylate. Reports describing the release of bisphenol-A from polymerized resin into saliva have aroused considerable concern regarding exposure to xenoestrogen by dental treatment. The purpose of the present study was to demonstrate a reliable methodology of detecting the trace amounts of bisphenol-A in dental materials. Bisphenol-A was separable from bisphenol-A diglycidyl methacrylate, which is often employed as the principal dimethacrylate monomer, by selective extraction with a Sep-Pak C18 cartridge. Using this extraction method in combination with a gas-chromatography mass-spectrometry, we have obtained evidence that all unpolymerized materials used in this study were contaminated with bisphenol-A. Quantitative analysis using a deuterium-labeled compound as an internal standard revealed bisphenol-A contents in commercial dental materials ranging from < 1 microgram/g material to about 20 micrograms/g material. The polymerized dental materials released up to 91.4 ng bisphenol-A/g material into phosphate buffered saline during 24-h incubation. These results indicate that bisphenol-A can be released from dental materials, however the leachable amount would be less than 1/1000 of the reported dose (2 micrograms/kg body weight/day) required for xenoestrogenisity in vivo.     

Human peripheral blood monocytes versus THP-1 monocytes for in vitro biocompatibility testing of dental material components

Monocytes play a central role in the response of tissues to biomaterials. Monocytic cell lines such as the THP-1 cell line have been used extensively as models for primary monocytes (directly from blood) in biocompatibility research. However, little information exists about the appropriateness of these cell lines as models. Thus, the current study compared the biological response of both primary peripheral blood monocytes (PBMs) and the THP-1 cell line to four common components of dental materials known to be released into the oral environment: nickel ions, 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4(2-hydroxy-3-methacryloloxy)-phenyl]propane (Bis-GMA). Comparisons were made by constructing dose-response curves for each type of monocyte and the four components. The 50% cytotoxicity values (TC50 values) were then statistically compared. In addition, the response of the monocytes to the materials with and without lipopolysaccharide (LPS) stimulation were assessed by measuring TNF-alpha secretion from the monocytes. The results showed that the PBMs were 5-10 times less sensitive than the THP-1 monocytes to these dental components, but that both cell lines ranked the components identically. TNF-alpha secretion from both types of monocytes often showed similar trends, although some inconsistent results were noted. The current study supports the use of THP-1s as a model for ranking the cytotoxicity of components of dental biomaterials. Furthermore, the secretory activity of PBMs appears to be generally well represented by the THP-1s. However, sufficient differences between these cell types exist to recommend confirmation of any critical results obtained with THP-1s using PBMs.     

Properties of eight methacrylated beta-cyclodextrin composite formulations.

OBJECTIVES: Methacrylated beta-cyclodextrins (MCDs) are novel candidate dental monomers if all or some of the hydroxyl groups of beta-cyclodextrin are substituted with methacrylate groups. The main objective of this study was to evaluate mechanical properties of a number of composite formulations having MCDs as novel dental comonomers. The properties determined were flexural strength (FS), volumetric shrinkage (VS), and degree of conversion (DC). METHODS: A mass fraction of 50% of MCD monomers was mixed with a mass fraction of 50% each of a series of dimethacrylate or monomethacrylate diluent comonomers to produce consistent formulations of a workable viscosity. For comparison a resin mixture of a mass fraction of 50% Bis-GMA and a mass fraction of 50% triethyleneglycol dimethacrylate (a typical dental resin mixture) was also studied. The mixtures were activated with camphorquinone and ethyl 4-dimethylamino benzoate. One part by mass of each activated resin formulation was mixed with three parts by mass of glass filler. Samples for the FS tests were prepared in (2 x 2 x 25) mm3 molds by light-curing the composites for 2 min on each side. The cured samples were immersed in 37 degrees C water for 24 h, and FS was measured with an Instron machine at a crosshead speed of 0.5 mm/min. VS was measured by a computer-controlled mercury dilatometer. DC was measured by near-infrared spectroscopy. RESULTS: The properties of the MCD-based composites depended on the kind of diluent used. With these MCD monomers, diluents of triethyleneglycol dimethacrylate, 1,10-decamethylenediol dimethacrylate, or benzyl methacrylate yielded the best composite properties. SIGNIFICANCE: Although not yet fully optimized, MCD-based composite formulations containing triethyleneglycol dimethacrylate, 1,10-decamethylenediol dimethacrylate, or benzyl methacrylate yielded flexural strength and volumetric shrinkage values were comparable to those of the Bis-GMA/triethyleneglycol dimethacrylate controls. These findings lend support for further development and evaluations of polymerizable cyclodextrin derivatives for use in dental materials.     

Physicomechanical evaluation of low-shrinkage dental nanocomposites based on silsesquioxane cores

This study aimed to determine the modulus, hardness, and polymerization shrinkage of novel silsesquioxane (SSQ)-based nanocomposites synthesized for dental applications. Four novel SSQ materials were developed and mixed with control monomers in 5, 10, 20, and 50 wt% SSQ nanocomposite ratios and were evaluated for use as potential low-shrinkage composite restoratives. The postgel polymerization shrinkage of the hybrid materials was then investigated and compared with unfilled 1:1 (control) bisphenol A glycerolate (1 glycerol/phenol) dimethacrylate/tri(ethylene glycol) dimethacrylate (Bis-GMA/TEGDMA) materials using a strain-monitoring device and test configuration. Mechanical properties, such as hardness and modulus, were determined using the depth-sensing microindentation approach. All samples investigated were polymerized using a dental light-curing unit (BISCO VIP) at 500 mW cm(-2) for 40 s. The results obtained were analyzed using analysis of variance/Scheffe's posthoc test at a significance level of 0.05. At 60 min postlight polymerization, postgel shrinkage associated with the control was found to be significantly higher than for all control/SSQ mixtures. Hardness and modulus were found to decrease with increased amount of SSQ monomers added, indicating that the incorporation of SSQ monomers into the control generally helps to reduce both the rigidity and the polymerization shrinkage. Therefore, in the correct formulation, SSQ materials have great potential to be used as low-shrinkage composite restoratives.     

Dimethacrylate monomers with varied fluorine contents and distributions.

OBJECTIVES: There are many unique properties associated with fluorinated polymers that make these materials attractive for use in the challenging oral environment. This study was devised to better define the influence of fluorine content and its structural distribution on properties of fluorinated resins and composites, especially with regard to their water-related and mechanical properties. METHODS: A series of fluorinated dimethacrylate monomers was prepared by reaction of aromatic diepoxides with fluoroalcohols and subsequent conversion of the resulting diols to the methacrylates. Composites based on monomer systems comprised of the fluorinated monomers with 1,10-decamethylene dimethacrylate and reinforced with silanized quartz filler were evaluated for conversion, water contact angle, water sorption and diametral tensile strength. RESULTS: By selection of reactants, fluorine was introduced as trifluoromethyl groups, extended fluoroalkyl pendant chains, or combinations of the two. Photopolymerization conversion among the experimental composites was generally equal to or greater than that of a conventional Bis-GMA/TEGDMA composite. While the water contact angles generally increased with fluorine content, no correlation was obtained between fluorine content and water sorption of the composites. The mechanical strength of the fluorinated composites showed a general decline with increasing fluorine content and consistent variations due to specific structural features. SIGNIFICANCE: A versatile route to fluorinated dimethacrylates with diverse structural and fluorine distribution patterns is presented. Composites from these monomers are very hydrophobic but have relatively low mechanical strength. The monomers described can be considered as useful additives to moderate the water sorption of conventional resins. However, the results of this study point to specific fluorinated resin structures that are expected to provide a more optimal balance between hydrophobicity and mechanical strength that will improve the long-term performance of dental composites.     

Susceptibility to discoloration of dental restorative materials containing dimethacrylate resin after bleaching

Odontology - The aim of this study is to compare the susceptibility to discoloration of dental restorative materials containing dimethacrylate resin after bleaching. In this study, resin-modified...     

Stability of bisphenol A, triethylene-glycol dimethacrylate, and bisphenol A dimethacrylate in whole saliva.

OBJECTIVES: This study investigated the stability of compounds of dental sealant materials in a salivary matrix. METHODS: Various amounts of bisphenol A (BPA), bisphenol A dimethacrylate (BIS-DMA) or triethylene-glycol dimethacrylate (TEGDMA) were added to whole salivary samples, and stored at -70 degrees C or -20 degrees C for up to 4 months. In other experiments, four separate whole salivary or water samples with BIS-DMA (200 ng/ml) were incubated for 0, 1, 2, 4 or 24h at 37 degrees C. Levels of analytes were determined by capillary gas chromatography/mass spectrophotometry (GC/MS) and high-performance liquid chromatography (HPLC). RESULTS: BPA was stable under all tested conditions. Samples originally containing BIS-DMA had high levels of BPA and almost no BIS-DMA after 4 months at -20 degrees C. Salivary samples incubated at 37 degrees C originally containing only BIS-DMA (200 ng/ml) demonstrated rapid decreases of BIS-DMA and increases of BPA. By 24h, the mean BIS-DMA concentration fell to 21.8 (25) ng/ml, while BPA increased to 100 (48) ng/ml. Only slight decreases in BIS-DMA and no BPA were present in the water samples incubated at 37 degrees C. BPA, BIS-DMA, and TEGDMA were stable if salivary samples were stored at -70 degrees C. Acidification of salivary samples prevented the breakdown of BIS-DMA. SIGNIFICANCE: BIS-DMA is converted rapidly to BPA in the presence of whole saliva. This could account for the findings of BPA in clinical samples collected after the placement of certain sealant products. Decreasing salivary pH and temperature can slow this process and this method should be used for clinical studies of salivary BPA leached from restorative materials.     

Monomer permeability of disposable dental gloves

STATEMENT OF PROBLEM: Studies have suggested that monomers may be able to permeate dental gloves. PURPOSE: This study examined the permeability of disposable dental gloves to 6 kinds of dental monomers. MATERIAL AND METHODS: The permeability of 6 kinds of dental monomers (methyl methacrylate [MMA], 2-hydroxyethyl methacrylate [HEMA], triethyleneglycol methacrylate [TEGDMA], ethyleneglycol dimethacrylate [EGDMA], urethane dimethacrylate [UDMA], and Bis-glycidyl methacrylate [Bis-GMA]) through 5 kinds of dental gloves (latex, powder-free latex, coated latex, polychloroprene, and polyvinyl chloride) was examined for up to 180 minutes at 37 degrees C. The fingers of unused gloves without pin holes were cut and used in the experiments. Five specimens per test group were examined. One type of monomer was poured into each finger and dipped in ethanol. The ethanol for extraction was measured by a spectrophotometer at a wavelength of 210 nm, and the results were analyzed by analysis of variance and the Kruskal-Wallis test (P<.05). RESULTS: Four of the monomers tested (MMA, HEMA, TEGDMA, and EGDMA) permeated the gloves tested, whereas 2 (UDMA and Bis-GMA) did not (P>.01). The amount of monomers permeating the latex in 10 minutes was 0.8 +/- 0.6, 0.6 +/- 0.6, 0.07 +/- 0.1, 0.07 +/- 0.1, 0.1 +/- 0.1 and 0.06 +/- 0.1 microL/mL for MMA, HEMA, EGDMA, TEGDMA, UDMA, and Bis-GMA, respectively. The amount of permeated monomer was then increased in relation to the examination time, and in MMA and HEMA, permeation occurred rapidly during the initial 60 minutes at 3 times the 10-minute values, then continued gradually and linearly. The polyvinyl chloride glove showed the greatest monomer permeability. Two-way analysis of variance showed significant correlations between MMA, HEMA, EGDMA or TEGDMA and UDMA or Bis-GMA (P<.01). Statistical significance was shown between polyvinyl chloride and latex, powder-free latex, coated latex or polychloroprene (P<.01). However, there was no significant relation between any kind of dental monomer and any kind of dental glove. CONCLUSION: Within the limitations of this study, 4 of the monomers tested permeated all of the gloves tested.     

Physical and mechanical properties of an experimental dental composite based on a new monomer.

OBJECTIVE: The purpose of this study was to investigate the physical and mechanical properties of a dental composite based on BTDMA, a new dimethacrylate monomer based on BTDA (3,3',4,4'-benzophenone tetracarboxylic dianhydride), and to compare these with the properties of a composite based on commonly used Bis-GMA monomer. METHODS: Experimental composites were prepared by mixing the silane-treated filler with the monomers. The prepared pastes were inserted into the test molds and heat-cured. Light-cured composites were also prepared using camphorquinone and amine as photoinitiator system. Degree of conversion of the light-cured and heat-cured composites was measured using FTIR spectroscopy. The flexural strength, flexural modulus, diametral tensile strength (DTS), water sorption, water contact angle, microhardness and thermal expansion coefficient of the prepared composites were measured and compared. Water uptake of the monomers was also measured. RESULTS: The results showed that the mechanical properties of the new composite are comparable with the properties of the Bis-GMA-based composite but its water sorption is higher. BTDMA as a monomer containing aromatic rings and carboxylic acid groups in its structure gives a composite with good mechanical properties. There is a close relation between the contact angle, water sorption of the cured composite and water uptake of their monomers. SIGNIFICANCE: Finding new monomers as alternatives for Bis-GMA have been a challenge in the field of dental materials and any investigation into the properties of new composites would be beneficial in the development of dental materials.     

Evaluation of residual monomer elimination methods in three different fissure sealants in vitro

The aim of this study was to determine the concentration of residual monomers and to evaluate the effectiveness of elimination methods of residual monomers in three different fissure sealant materials (Helioseal F, Filtek Flow and EXM-510). The sealant materials were divided into four subgroups because of the treatment methods used; one control group and three experimental groups (cotton roll, rubber cup and prophylaxis paste in cup). High performance liquid chromatography was used to determine the concentrations of residual monomers. Results of the study showed that residual Bis-glycidyl dimethacrylate elution was the highest in Helioseal F and the lowest in Filtek Flow with the three methods tested. For triethleneglycol dimethacrylate, EXM-510 eluted the highest residual monomer. It was also found that although the three tested methods were insufficient for removing all of the residual monomers and rubbing with cotton rolls was more effective than other two methods.