Extrapolation of cytotoxic masked effects in planar in vitro assays.

The masking of specific effects in in vitro assays by cytotoxicity is a commonly known phenomenon. This may result in a partial or complete loss of effect signals. For common in vitro assays, approaches for identifying and quantifying cytotoxic masking are partly available. However, a quantification of cytotoxicity-affected signals is not possible. As an alternative, planar bioassays that combine high-performance thin layer chromatography with in vitro assays, such as the planar yeast estrogen screen (p-YES), might allow for a quantification of cytotoxically affected signals. Affected signals form a typical ring structure with a supressed or completely lacking centre that results in a double peak chromatogram. This study investigates whether these double peaks can be used for fitting a peak function to extrapolate the theoretical, unaffected signals. The precision of the modelling was evaluated for four individual peak functions, using 42 ideal, undistorted peaks from estrogenic model compounds in the p-YES. Modelled ED50-values from bisphenol A (BPA) experiments with cytotoxically disturbed signals were 13 times higher than for the apparent data without compensation for cytotoxicity (320 ± 63 ng versus 24 ± 17 ng). This finding has a high relevance for the modelling of mixture effects according to concentration addition that requires unaffected, complete dose-response relationships. Finally, we applied the approach to results of a p-YES assay on leachate samples of an elastomer material used in water engineering. In summary, the fitting approach enables the quantitative evaluation of cytotoxically affected signals in planar in vitro assays and also has applications for other fields of chemical analysis like distorted chromatography signals.

Planar chromatography-bioassays for the parallel and sensitive detection of androgenicity, anti-androgenicity and cytotoxicity.

Anti-androgens entering the aquatic environment, e.g., by effluents from wastewater treatment plants or agricultural settings are contributing to endocrine disruption in wildlife and humans. Due to the simultaneous presence of agonistic compounds, common in vitro bioassays can underestimate the risk posed by androgen antagonists. On the other hand, cytotoxic effects might lead to false positive assessments of anti-androgenic effects in conventional bioassays. In the present study, a combination of normal phase high-performance thin-layer chromatography (NP-HPTLC) with a yeast-based reporter gene assay is established for the detection of anti-androgenicity as a promising tool to reduce interferences of androgenic and anti-androgenic compounds present in the same sample. To avoid a misinterpretation of anti-androgenicity with cytotoxic effects, cell viability was assessed in parallel on the same plate using a resazurin viability assay adapted to HPTLC plates. The method was characterized by establishing dose-response curves for the model compounds flutamide and bisphenol A. Calculated effective doses at 10% (ED10) were 27.9 ± 1.3 ng zone-1 for flutamide and 20.1 ± 5.1 ng zone-1 for bisphenol A. Successful distinction between anti-androgenicity and cytotoxicity was exemplarily demonstrated with 4-nitroquinoline 1-oxide. As a proof of concept, the detection and quantification of anti-androgenicity in an extract of a landfill leachate is demonstrated. This study shows that the hyphenation of HPTLC with the yeast anti-androgen screen is a matrix-robust, cost-efficient and fast screening tool for the sensitive and simultaneous detection of anti-androgenic and cytotoxic effects in environmental samples. The method offers a wide range of possible applications in environmental monitoring and contributes to the identification of anti-androgenicity drivers in the course of an effect-directed analysis.

Development and validation of a parent-proxy health-related quality of life survey for Australian First Nations children.

OBJECTIVE: Within Australia, Aboriginal and Torres Strait Islander (First Nations) populations perceive health and well-being differently to non-Indigenous Australians. Existing health-related quality of life (HR-QoL) measurement tools do not account for these differences. The objective of this study was to develop and validate a culturally specific parent-proxy HR-QoL measurement tool for First Nations children. DESIGN: Scale development was informed by parents/carers of children with a chronic illness and an expert panel. The preliminary 39-item survey was reviewed (n=12) and tested (n=163) with parents/carers of First Nations children aged 0-12 years at baseline with comparative scales: the Kessler Psychological Distress Scale, generic HR-QoL (Paediatric QoL Inventory 4.0, PedsQL4.0) and Spence Children's Anxiety Scale, and repeated (n=46) 4 weeks later. Exploratory Factor Analysis was used for scale reduction. Reliability and validity were assessed by internal consistency, test-retest, and correlations with comparison scales. RESULTS: Items within our First Nations-Child Quality of Life (FirstNations-CQoL) were internally consistent with Cronbach's alpha coefficients of ≥0.7 (quality of life, 0.808; patient experience, 0.880; patient support, 0.768) and overall test-retest reliability was good (r=0.75; 95% CI 0.593 to 0.856). Convergent validity was observed with the PedsQL4.0 with Pearson's coefficients of r=0.681 (ages 2-4 years); r=0.651 (ages 5-12 years) and with the Kessler Psychological Distress scale (r=-0.513). Divergent validity against the Spence Anxiety Scale was not demonstrated. CONCLUSIONS: The FirstNations-CQoL scale was accepted by the participants, reliable and demonstrated convergent validity with comparison measures. This tool requires further evaluation to determine responsiveness, its minimal important difference and clinical utility.

UV aged epoxy coatings - Ecotoxicological effects and released compounds.

Organic coatings can guarantee long-term protection of steel structures due to causing a physical barrier against water and oxygen. Because of their mechanical properties and resistances to heat and chemicals, epoxy resin-based coatings are widely used for corrosion protection. Despite of the aromatic backbone and the resulting susceptibility to UV degradation, epoxy resins are frequently used as binding agent in top layers of anti-corrosion coating systems. Consequently, these organic polymers are directly exposed to sunlight and thus UV radiation. The present study was designed to investigate if toxic effects of epoxy resin-based-coatings are changed by UV-A irradiation. For this purpose, two epoxide-based top coatings were examined with and without UV aging for their bacterial toxicity and estrogenicity. In addition, chemical analyses were performed to identify released compounds as well as photolytic degradation products and to assign toxic effects to individual substances. UV-A irradiation of epoxy resin based top coatings resulted in an overall decrease of acute and specific ecotoxicological effects but as well to the formation of toxic transformation products. Both, in leachates of untreated and UV-A irradiated coatings, 4tBP was identified as the main driver of estrogenicity and toxicity to luminescent bacteria. BPA and structural analogs contributing to estrogenic effects in leachates were formed by UV-A irradiation. The combination of HPTLC coupled bioassays and LC-MS analyses supported the identification of bioactive compounds in terms of an effect-directed analysis. The present findings indicate that epoxide-based coatings are less suitable for the application as top coatings and more UV stable coatings like aliphatic polyurethanes should be preferred.

Determination of metal uptake in single organisms, Corophium volutator, via complementary electrothermal vaporization/inductively coupled plasma mass spectrometry and laser ablation/inductively coupled plasma mass spectrometry.

RATIONALE: (Eco-)toxicological effects are mostly derived empirically and are not correlated with metal uptake. Furthermore, if the metal content is determined, mostly bulk analysis of the whole organism population is conducted; thus, biological variability is completely disregarded, and this may lead to misleading results. To overcome this issue, we compared two different solid sampling techniques for the analysis of single organisms. METHODS: In this study, complementary electrothermal vaporization/inductively coupled plasma mass spectrometry (ETV/ICP-MS) ⇔ laser ablation/inductively coupled plasma mass spectrometry (LA/ICP-MS)-based methods for the analysis of individual organisms were developed and the results obtained were compared with the concentrations obtained after digestion and measured using ICP-MS. For this purpose, a common (eco-)toxicological test organism, the mud shrimp Corophium volutator, was selected. As proof-of-concept application, these organisms were incubated with environmentally relevant metals from galvanic anodes, which are often used for protection against metal corrosion in, for example, offshore wind farms. RESULTS: The bulk analysis revealed that large quantities of the incubated elements were detectable. Using the ETV/ICP-MS method, we could identify a high biovariability within the population of organisms tested. Using the LA/ICP-MS method, it could be determined that the large quantities of the elements detected were due to adsorption of the metals and not due to uptake, which correlates well with the absence of (eco-)toxicological effects. CONCLUSIONS: The results obtained imply the efficiency of complementary methods to explain the absence or presence of (eco-)toxicological effects. In particular, methods that allow for single-organism analysis or provide even a spatial resolution support the interpretation of ecotoxicological findings.

What not to expect when you're expecting - Postpartum proximal ureteric rupture: A case report.

INTRODUCTION: Spontaneous ureteric rupture is an extremely rare cause of acute abdominal pain in the intrapartum and postpartum period. We present the case of a right ureteric rupture diagnosed immediately postpartum. CASE: A 23-year-old woman in her second pregnancy (who had had a previous caesarean section) developed acute-onset right-flank pain 12 h after vaginal delivery. A contrast computerized tomography scan suggested a ureteric injury; ureteroscopy diagnosed a proximal ureteric rupture and a stent was placed. DISCUSSION: This case outlines an extremely rare cause of abdominal pain in the peripartum. There can be serious complications, including urinoma, abscess and sepsis, and therefore the diagnosis should not be delayed.

Ecotoxicological characterization of emissions from steel coatings in contact with water.

In order to prevent corrosion damage, steel structures need to be protected. Coating systems achieve this by the isolation of the steel from its environment. Common binding agents are epoxide and polyurethane resins which harden by polyaddition reactions. In contact with water, various organic substances might be leached out and released into the aquatic environment potentially causing adverse effects. So far, no legal requirements are mandatory for the environmental sustainability of coating systems. To characterize emissions from steel coatings, recommendations for the ecotoxicological assessment of construction products were utilized. Seven different coating systems based on epoxide or polyurethane resins were leached in 8 steps (6 h-64 d), followed by the testing of acute toxic effects on bacteria and algae as well as estrogen-like and mutagenic effects. In addition, chemical analysis by GC-MS was performed to identify potentially toxic compounds released from the coating systems. Two systems tested did not show any significant effects in the bioassays. One coating system caused significant algal toxicity, none was found to cause mutagenic effects. The other coating systems mainly showed estrogenic effects and bacterial toxicity. The effects increased with increasing leaching time. 4-tert-butylphenol, which is used in epoxy resins as a hardener, was identified as the main contributor to acute and estrogenic effects in two coatings. The release mechanism of 4-tert-butylphenol was characterized by two different modelling approaches. It was found that the release from the most toxic coating is not explainable by an elevated content of 4-tert-butylphenol but more likely by the release mechanism that - in contrast to the less toxic coating - is controlled not only by diffusion. This finding might indicate a sub-optimal formulation of this coating system resulting in a less stable layer and thus an increased release of toxic compounds.

Communication between mast cells and rat submucosal neurons.

Histamine is a mast cell mediator released e.g. during food allergy. The aim of the project was to identify the effect of histamine on rat submucosal neurons and the mechanisms involved. Cultured submucosal neurons from rat colon express H1, H2 and H3 receptors as shown by immunocytochemical staining confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) with messenger RNA (mRNA) isolated from submucosal homogenates as starting material. Histamine evoked a biphasic rise of the cytosolic Ca(2+) concentration in cultured submucosal neurons, consisting in a release of intracellularly stored Ca(2+) followed by an influx from the extracellular space. Although agonists of all three receptor subtypes evoked an increase in the cytosolic Ca(2+) concentration, experiments with antagonists revealed that mainly H1 (and to a lesser degree H2) receptors mediate the response to histamine. In coculture experiments with RBL-2H3 cells, a mast cell equivalent, compound 48/80, evoked an increase in the cytosolic Ca(2+) concentration of neighbouring neurons. Like the response to native histamine, the neuronal response to the mast cell degranulator was strongly inhibited by the H1 receptor antagonist pyrilamine and reduced by the H2 receptor antagonist cimetidine. In rats sensitized against ovalbumin, exposure to the antigen induced a rise in short-circuit current (I sc) across colonic mucosa-submucosa preparations without a significant increase in paracellular fluorescein fluxes. Pyrilamine strongly inhibited the increase in I sc, a weaker inhibition was observed after blockade of protease receptors or 5-lipoxygenase. Consequently, H1 receptors on submucosal neurons seem to play a pivotal role in the communication between mast cells and the enteric nervous system.

Different occupations associated with amyotrophic lateral sclerosis: is diesel exhaust the link?

The cause of sporadic amyotrophic lateral sclerosis (SALS) remains unknown. We attempted to find out if occupational exposure to toxicants plays a part in the pathogenesis of this disease. In an Australia-wide case-control study we compared the lifetime occupations of 611 SALS and 775 control individuals. Occupations were coded using country-specific as well as international classifications. The risk of SALS for each occupation was calculated with odds ratios using logistic regression. In addition, the literature was searched for possible toxicant links between our findings and previously-reported occupational associations with SALS. Male occupations in our study that required lower skills and tasks tended to have increased risks of SALS, and conversely, those occupations that required higher skills and tasks had decreased risks of SALS. Of all the occupations, only truck drivers, where exposure to diesel exhaust is common, maintained an increased risk of SALS throughout all occupational groups. Another large case-control study has also found truck drivers to be at risk of SALS, and almost two-thirds of occupations, as well as military duties, that have previously been associated with SALS have potential exposure to diesel exhaust. In conclusion, two of the largest case-control studies of SALS have now found that truck drivers have an increased risk of SALS. Since exposure to diesel exhaust is common in truck drivers, as well as in other occupations that have been linked to SALS, exposure to this toxicant may underlie some of the occupations that are associated with SALS.

Actions of Angeli's salt, a nitroxyl (HNO) donor, on ion transport across mucosa-submucosa preparations from rat distal colon.

The aim of this study was to investigate whether nitroxyl (HNO), a redox variant of the radical gasotransmitter nitric oxide (NO) with therapeutically promising properties, affects colonic ion transport. Changes in short-circuit current (Isc) induced by the HNO donor Angeli's salt were recorded in Ussing chambers. Cytosolic Ca(2+) concentration was measured with fura-2. The nitroxyl donor induced a concentration-dependent increase in Isc across rat distal colon which was due to a stimulation of chloride secretion. The secretion induced by Angeli's salt (5×10(-4)mol/l) was not altered by the NO scavenger 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide (carboxy-PTIO), but was abolished by the HNO scavenger l-cysteine. The response was not dependent on the activity of soluble guanylate cyclase or enteric neurons, but was inhibited by indomethacin. Experiments with apically permeabilized epithelia revealed the activation of basolateral K(+) channels and a stimulation of the current carried by the basolateral Na(+)-K(+)-pump by Angeli's salt. The secretion induced by Angeli's salt was reduced in the absence of extracellular Ca(2+). A prominent increase in the cytosolic Ca(2+) concentration was evoked by Angeli's salt predominantly in subepithelial cells within the submucosa, which had the same dependence on extracellular Ca(2+) as the Angeli's salt-induced Cl(-) secretion. Consequently, Angeli's salt induces a soluble guanylate cyclase-independent, Ca(2+)-dependent Cl(-) secretion via activation of the Na(+)-K(+)-ATPase and of basolateral K(+) channels. Cyclooxygenase metabolites produced within the submucosa seem to be involved in this response.

Distribution of voltage-dependent and intracellular Ca2+ channels in submucosal neurons from rat distal colon.

We recently observed a bradykinin-induced increase in the cytosolic Ca2+ concentration in submucosal neurons of rat colon, an increase inhibited by blockers of voltage-dependent Ca2+ (Ca(v)) channels. As the types of Ca(v) channels used by this part of the enteric nervous system are unknown, the expression of various Ca(v) subunits has been investigated in whole-mount submucosal preparations by immunohistochemistry. Submucosal neurons, identified by a neuronal marker (microtubule-associated protein 2), are immunoreactive for Ca(v)1.2, Ca(v)1.3 and Ca(v)2.2, expression being confirmed by reverse transcription plus the polymerase chain reaction. These data agree with previous observations that the inhibition of L- and N-type Ca2+ currents strongly inhibits the response to bradykinin. However, whole-cell patch-clamp experiments have revealed that bradykinin does not enhance Ca2+ inward currents under voltage-clamp conditions. Consequently, bradykinin does not directly interact with Ca(v) channels. Instead, the kinin-induced Ca2+ influx is caused indirectly by the membrane depolarization evoked by this peptide. As intracellular Ca2+ channels on Ca(2+)-storing organelles can also contribute to Ca2+ signaling, their expression has been investigated by imaging experiments and immunohistochemistry. Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) have been functionally demonstrated in submucosal neurons loaded with the Ca(2+)-sensitive fluorescent dye, fura-2. Histamine, a typical agonist coupled to the phospholipase C pathway, induces an increase in the fura-2 signal ratio, which is suppressed by 2-aminophenylborate, a blocker of IP3 receptors. The expression of IP3R1 has been confirmed by immunohistochemistry. In contrast, ryanodine, tested over a wide concentration range, evokes no increase in the cytosolic Ca2+ concentration nor is there immunohistochemical evidence for the expression of ryanodine receptors in these neurons. Thus, rat submucosal neurons are equipped with various types of high-voltage activated Ca(v) channels and with IP3 receptors for intracellular Ca2+ signaling.

Characterization of VAMP-2 in the lung: implication in lung surfactant secretion.

Lung surfactant is crucial for reducing the surface tension of alveolar space, thus preventing the alveoli from collapse. Lung surfactant is synthesized in alveolar epithelial type II cells and stored in lamellar bodies before being released via the fusion of lamellar bodies with the apical plasma membrane. SNAREs (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptors) play an essential role in membrane fusion. We have previously demonstrated the requirement of t-SNARE (target SNARE) proteins, syntaxin 2 and SNAP-23 (N-ethylmaleimide-sensitive factor-attachment protein 23), in regulated surfactant secretion. Here, we characterized the distribution of VAMPs (vesicle-associated membrane proteins) in rat lung and alveolar type II cells. VAMP-2, -3 and -8 are shown in type II cells at both mRNA and protein levels. VAMP-2 and -8 were enriched in LB (lamellar body) fraction. Immunochemistry studies indicated that VAMP-2 was co-localized with the LB marker protein, LB-180. Functionally, the cytoplasmic domain of VAMP-2, but not VAMP-8 inhibited surfactant secretion in type II cells. We suggest that VAMP-2 is the v-SNARE (vesicle SNARE) involved in regulated surfactant secretion.

Hospitalizations Due to Respiratory Syncytial Virus Outside of the Typical Season.

Objective: Respiratory Syncytial Virus (RSV) is the most common cause of bronchiolitis and viral lower respiratory tract infections in children. It is associated with annual winter epidemics across the United States, typically October through April. Our objective is to describe the clinical characteristics of children hospitalized outside the typical RSV season and to compare them with those admitted during the season. Methods: A retrospective chart review was conducted of all patients who were hospitalized at Children's Hospital of Austin from May 2000 to September 2006 and had a positive RSV antigen test. Descriptive statistics, tests of differences, and associations between patients diagnosed in the off-season versus typical season were conducted. Results: A total of 850 charts of RSV-positive cases were reviewed. Of these, 45 patients (5.3%) were admitted during the off-season. The following variables were statistically significantly associated with diagnosis in the off-season versus typical season: mean birth weight (2704 g vs. 3204 g respectively, p=0.0001); gestational age at birth less than 36 weeks (OR=4.35; 95% CI: 2.2, 8.6); history of neonatal intensive care unit (NICU) admission at birth (OR=6.04; 95% CI: 2.9, 12.5); and multiple birth (OR=3.38; 95% CI: 1.2, 9.2). Conclusions: Infants with RSV infection outside of the typical season were more likely to have been premature, of lower birth weight, the products of multiple births, and admitted to the NICU at birth.

Ionotropic GABA receptor expression in the lung during development.

Cl(-) transport is essential for lung development. Because gamma-aminobutyric acid (GABA) receptors allow the flow of negatively-charged Cl(-) ions across the cell membrane, we hypothesized that the expression of ionotropic GABA receptors are regulated in the lungs during development. We identified 17 GABA receptor subunits in the lungs by real-time PCR. These subunits were categorized into four groups: Group 1 had high mRNA expression during fetal stages and low in adults; Group 2 had steady expression to adult stages with a slight up-regulation at birth; Group 3 showed an increasing expression from fetal to adult lungs; and Group 4 displayed irregular mRNA fluctuations. The protein levels of selected subunits were also determined by Western blots and some subunits had protein levels that corresponded to mRNA levels. Further studied subunits were primarily localized in epithelial cells in the developing lung with differential mRNA expression between isolated cells and whole lung tissues. Our results add to the knowledge of GABA receptor expression in the lung during development.

Bonding of fibre-reinforced composite post to root canal dentin.

OBJECTIVE: The aim of this study was to determine bonding properties of two types of fibre-reinforced composite (FRC) posts cemented into root canals of molars. Serrated titanium posts served as reference. METHODS: Prefabricated carbon/graphite FRC posts with cross-linked polymer matrix and individually formed glass FRC posts with interpenetrating polymer network (IPN) polymer matrix were compared. The crowns of extracted third molars were removed and post space (diameter: 1.5mm) was drilled, etched and bonded. The posts were treated with dimethacrylate adhesive resin, light-polymerized and cemented with a dual-polymerizing composite resin luting cement. After thermocycling (6000x) the samples were cut into discs of thicknesses: 1, 2 and 4mm (n=12/group). Push-out force was measured by pushing the post from one end. Assessment of failure mode was made under a stereomicroscope (1, adhesive failure between post and cement; 2, cohesive failure of post-system; 3, adhesive failure between cement and dentin). RESULTS: The push-out force increased with increased height of dentin disc in all groups (ANOVA, p<0.001). In the 4mm thick dentin discs the individually formed glass FRC posts showed highest push-out force and the difference to that of the titanium posts was significant (ANOVA, p<0.001). The other differences were not statistically significant. None of the individually formed glass FRC posts showed adhesive failures between the post and the cement. CONCLUSIONS: Contrary to the other posts, there were no adhesive (post-cement) failures with the individually formed glass FRC posts, suggesting better interfacial adhesion of cement to these posts.

Flexural properties of fiber reinforced root canal posts.

OBJECTIVES: Fiber-reinforced composite (FRC) root canal posts have been introduced to be used instead of metal alloys and ceramics. The aim of this study was to investigate the flexural properties of different types of FRC posts and compare those values with a novel FRC material for dental applications. METHODS: Seventeen different FRC posts of various brands (Snowpost, Carbopost, Parapost, C-post, Glassix, Carbonite) and diameters, (1.0-2.1 mm) and a continuous unidirectional E-glass FRC polymerized by light activation to a cylindrical form (everStick, diameter 1.5 mm) as a control material were tested. The posts (n=5) were stored at room's humidity or thermocycled (12.000 x, 5 degrees C/55 degrees C) and stored in water for 2 weeks before testing. A three-point bending test (span=10 mm) was used to measure the flexural strength and modulus of FRC post specimens. RESULTS: Analysis of ANOVA revealed that thermocycling, brand of material and diameter of specimen had a significant effect (p<0.001) on the fracture load and flexural strength. The highest flexural strength was obtained with the control material (everStick, 1144.9+/-99.9 MPa). There was a linear relationship between fracture load and diameter of posts for both glass fiber and carbon fiber posts. Thermocycling decreased the flexural modulus of the tested specimens by approximately 10%. Strength and fracture load decreased approximately 18% as a result of thermocycling. SIGNIFICANCE: Considerable variation can be found in the calculated strength values of the studied post brands. Commercial prefabricated FRC posts showed lower flexural properties than an individually polymerised FRC material.

Bonding of composite resin luting cement to fiber-reinforced composite root canal posts.

PURPOSE: The aim of this study was to compare bonding of composite resin luting cement to a fiber-reinforced composite (FRC) root canal post with either a cross-linked or a semi-interpenetrating polymer network (IPN) polymer matrix. MATERIALS AND METHODS: Four different types of prefabricated FRC posts with a cross-linked polymer matrix and two types of FRC posts with a semi-IPN polymer matrix which were individually formed were tested. Serrated titanium posts served as the reference. An auto-polymerizing resin luting cement was used for cementing the posts into the holes of composite resin disks. The pull-out force was measured using a universal testing machine after the post/cement/disk system had been stored dry or thermocycled (5 degrees C/55 degrees C, 6000x) in water. The bonding sites of the posts were examined with SEM. RESULTS: The FRC posts with a semi-IPN polymer matrix gave significantly higher pull-out force values than the prefabricated FRC posts with a smooth surface and a cross-linked polymer matrix (p < 0.004). The highest pull-out force was obtained with serrated titanium posts. Both the type of FRC post and thermocycling had a significant effect on the pull-out force (n = 8, ANOVA p < 0.001 and p < 0.007, respectively). SEM photomicrographs confirmed the results. CONCLUSION: This study showed that FRC posts with a semi-IPN polymer matrix bonded better to composite resin luting cement than did prefabricated FRC posts with a cross-linked polymer matrix, although their pull-out force was not as high as that of the mechanically interlocked serrated titanium posts.

Depth of light-initiated polymerization of glass fiber-reinforced composite in a simulated root canal.

PURPOSE: The possibility of polymerizing glass fiber-reinforced composite (FRC) material into the root canal was preliminarily evaluated by determining the depth of light-initiated polymerization of FRC. MATERIALS AND METHODS: The material used was polymer-preimpregnated E-glass fiber reinforcement, which was further impregnated with light-polymerizable dimethacrylate monomer resin. The same resin without fiber reinforcement was used as a control. Six different lengths (range 4 to 24 mm) of light-protected cylinders filled with the test materials were light polymerized from one end. The degree of monomer conversion was determined from the other end by FT-IR spectrometry. Infrared spectra were recorded at six time points from the beginning of polymerization. The microhardness of the test materials was measured from the light-exposure surface toward the other end of the cylinder. RESULTS: Both groups showed a reduction in the degree of conversion with increased lengths of the cylinder. The FRC group showed a higher degree of conversion in the longest sample group compared to the resin group. Microhardness measurement confirmed the constant reduction of the degree of conversion by the reduced Vickers hardness values with increased cylinder length of the FRC. CONCLUSION: Generally, the glass FRC showed an almost equal degree of conversion after light curing as monomer resin without fibers. However, in the longest cylinders, FRC showed a slightly higher degree of conversion compared to resin only; this might be due to the fibers' ability to conduct light.