Release of Monomers from Dental Composite Materials into Saliva and the Possibility of Reducing the Toxic Risk for the Patient.

Background and Objectives: The objective of this study was (1) to measure the amount of monomers released into the saliva depending on the time elapsed after the hardening of the composite and on the type of monomer used; and (2) with the prolongation of the light-curing procedure, to publish information on whether it would be possible to influence the level of leached monomers. Materials and Methods: HPLC technique was used to monitor the levels of the unpolymerized monomers Bis-GMA, Bis/EMA, TEGDMA, and UDMA from the four commonly used composite materials, released into the saliva of a volunteer with intact dentition. The levels were monitored in 3 time periods during 24 h after composite hardening. From every composite material, 4 samples were formed and cured with an LED lamp for 10 s, 20 s, 40 s, and 60 s. After the light curing, the same polishing procedure was used and the samples were leached in blank saliva samples. Results: We observed that every monitored composite material eluted monomers into the saliva after its application. The amount of monomers depended on the time elapsed after the curing of the composite and on the type of composite used. A 40 s LED curing procedure can reduce the amount of leached monomers in comparison with the standard 20 s procedure, especially for monomers of higher molecular weight. Conclusions: Our study confirmed the hypothesis that the release of monomers gradually decreases with increasing time after the hardening of the composite filling.

Evaluation of the dentinal tubule penetration of an endodontic bioceramic sealer after three final irrigation protocols

Introduction: This study aimed to evaluate the dentinal tubule penetration of an endodontic bioceramic sealer, Sealer Plus BC, after three final irrigation protocols. Methods: Thirty distobuccal roots of maxillary molars were selected. Root canal preparation was performed up to an #40.06 instrument (X1 Blue) under 2.5% sodium hypochlorite irrigation. Specimens were randomly divided into three groups (n=10), according to the final irrigation protocol: G-NaOCl (2.5% sodium hypochlorite + PUI), G-SS (0.9% saline solution + PUI) and G-H20 (Deionized water + PUI). After final irrigation protocols, all specimens were irrigated with phosphate buffer solution. Root canal obturation was performed using the single cone technique and Sealer Plus BC, stained with a specific fluorophore. Specimens were transversely sectioned and each root third was evaluated in a confocal scanning laser microscopy. Images obtained were analyzed for sealer penetration in the dentinal tubules. Results: Dentinal tubule penetration of Sealer Plus BC was not observed in any root third, regardless of the final irrigation protocol investigated. Conclusions: Sealer Plus BC dentinal tubule penetration was not observed after none of the protocols tested. Dentinal tubule penetrability of Sealer Plus BC may be related to other factors rather than the final irrigation protocol.

Evaluation of Residual Monomers Eluted from Pediatric Dental Restorative Materials.

Unreacted monomers eluted from resin-based restorative materials have been considered a reason of local and systemic adverse reactions. This study was designed to determine the effect of finishing and polishing procedures on the elution of Bis-GMA, TEGDMA, UDMA, and HEMA monomers from compomer and bulk-fill composite resins. Bulk-fill composite (3M ESPE GmbH, Seefeld, Germany) and compomer (Dentsply DeTrey GmbH, Konstanz, Germany) specimens with 3 × 4 mm diameters were prepared. The specimens were randomly divided into two groups, and finishing-polishing procedures were applied only to the experimental groups. Release of residual monomers was analyzed by using High-Performance Liquid Chromatography (HPLC) after 24, 48, and 72 hours. Repeated measures ANOVA and Tukey post hoc tests were used for comparisons. Finishing and polishing procedures had a significant effect on reducing the quantity of UDMA release in the Filtek™ Bulk Fill composite and Bis-GMA, HEMA, and TEGDMA in the Dyract XP compomer (p < 0.05). The restorative materials investigated here are not chemically stable after polymerization, and concentrations of eluted monomers may reach critical toxicity levels even after one restoration placement. Finishing and polishing procedures are mandatory to reduce residual monomers.

Detección mediante técnica de GCMS de alto contenido de Bisfenol A en cementos de uso endodóntico / Bisfenol a; endodoncia; obturación bisphenol a determination by gcms in resin-based root canal sealers

El bisfenol A (BPA, por sus siglas en inglés) es un producto químico utilizado en la producción de policarbonatos y resinas epoxi, cuyo uso está muy extendido en la industria. El BPA puede pasar al organismo por medio de la dieta, ya que sus moléculas tienen migración probable de los recipientes fabricados con este producto a los alimentos contenidos en dichos recipientes. La presencia de BPA en los materiales de uso odontológico está muy extendida. Una gran cantidad de productos están elaborados con resinas epoxi (procedentes de la reacción entre la epiclorohidrina y el bisfenol A). El presente estudio se analizaron cuatro cementos de uso endodóntico basados en resina (Ah 26(R), Ah Plus(R), TopSeal(R) y Simpliseal(R)) a través de un procedimiento de extracción líquido-sólido y análisis en cromatógrafo de gases acoplado a espectrometría de masas. Los resultados obtenidos muestran valores alarmantemente superiores a los 5x10-6% en peso que permite la Unión Europea para la migración de BPA desde el envase al alimento, obteniéndose unos valores de 7% (Simpliseal(R)); 22% (AH 26(R)); 46% (TopSeal(R)) y 74% (AH Plus(R)). El presente estudio es pionero en el estudio de la concentración de BPA en materiales endodónticos

Bisphenol A (BPA) is a compound used in the production of polycarbonates and epoxy resins and is widely used in the industry. BPA can be passed into the body through the diet, since its molecules can easily migrate from the containers made with BPA to the food in those containers. The presence of BPA in dental materials is very common. A large number of products are made with epoxy resins (from the reaction between epichlorohydrin and bisphenol A). This study analyzed four resin-based endodontic cements (Ah 26(R), Ah Plus(R), TopSeal(R) and Simpliseal(R)) using a liquid-solid extraction procedure and gas chromatograph analysis coupled to mass spectrometry. The results obtained show alarmingly higher values than the 5x10-6% by weight that the European Union allows for the migration of BPA from packaging to food, obtaining values of 7% (Simpliseal(R)), 22% (AH 26(R)), 46% (TopSeal(R)) and 74% (AH Plus(R)). This study is a pioneer in the investigation of the concentration of BPA in endodontic materials

Assessment of monomer release from 3 different fissure sealants.

BACKGROUND: Light-activated resin-based dental fissure sealants are the most widely accepted among clinicians. The objective of this study was to determine monomer release of 3 different light-curing fissure sealants in vitro: Control Seal (Voco, Germany), Fissurit FX (Voco, Germany) and R&D Series Fissured Nova (Imicrly, Turkey). METHODS: Each material was polymerized with a curing light: Valo Cordless (Ultradent) LED in standard mode for 20 seconds (n = 27) and 40 seconds (n = 27) and in Xtra power mode (plasma arc) for 3 seconds (n = 27). High-performance liquid chromatography (HPLC) was used to measure the amount of monomers released over 1, 3 and 7 days. RESULTS: Plasma arc groups showed the highest release of monomers at 1, 3 and 7 days in the 3 fissure sealant groups (p<0.001). The greatest release of bisphenol A glycidyl methacrylate (bis-GMA) determined for R&D Series Fissured Nova both with LED 20 seconds and LED 40 seconds and for Control Seal was with the plasma arc. With time, release of the monomer was reduced for all polymerization systems. CONCLUSIONS: Efficiency of the polymerization system and applying the recommended curing time for light-activated resin-based dental materials are very important to protect the patient from potential hazards of residual monomers.

Morphological and immunohistochemical analysis of the biocompatibility of resin-modified cements.

The aim of this double-blind randomized study was to evaluate the biocompatibility of resin-modified glass ionomer cements (RMGIC) by means of morphological and immunohistochemical analyses. RMGICs were selected and divided into four groups: Group CK (Crosslink Orthodontic Band Cement); Group RS (Resilience Light Cure Band Cement) Group RMO (RMO Band Cement), Group TP (Transbond Plus Light Cure Band), and Group C (Control-polyethylene). The materials were implanted in rat subcutaneous tissues, randomly selected for this study. After time intervals of 7, 15, and 30 days the tissues were submitted to morphological analysis. In immunohistochemical analysis, the immuno-marking of antibody CD68 was evaluated. The results obtained were statistically analyzed by the Kruskal-Wallis and Dunn tests (p < .05). In the morphological analysis after 7 days, Groups RS, RMO and TP showed more intense inflammatory infiltrate (p = .004) and only Group RMO presented greater intensity of multinucleated giant cells (p = .027). In the immunohistochemical analysis, Groups RMO and RS were observed to present a larger quantity of CD68+ (p = .004) in the time interval of 7 days and only Group RMO presented statistically significant difference for this parameter after 15 days (p = .026). In the time interval of 30 days, Group RMO presented the largest quantity of multinucleated giant cells (p < .004). The RMGICS Crosslink and Transbond Plus provided significantly better tissue biocompatibility than the Resilience and RMO Cements.

Release of monomers from orthodontic adhesives.

INTRODUCTION: Most composite resins release both bisphenol A (BPA), which disrupts the endocrine balance, and triethylene glycol dimethacrylate (TEGDMA), which has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to characterize monomers released from orthodontic adhesives. METHODS: We studied samples of orthodontic adhesives by associating 2 techniques: gas phase chromatography and mass spectrometry. RESULTS: The in-vitro analysis detected significant quantities of BPA, TEGDMA, and other monomers in orthodontic adhesives used in daily practice: Transbond XT, Transbond Supreme LV (both, 3M Unitek, Monrovia, Calif), Blugloo (Ormco, Orange, Calif), and MonoLok 2 (Rocky Mountain Orthodontics, Denver, Colo). CONCLUSIONS: Clinicians should consider that orthodontic adhesives contain BPA, an endocrine disruptor; TEGDMA, an allergic and a cytotoxic compound; and carcinogenic genotoxic compounds. These molecules are not mentioned in the material safety data sheets. Manufacturers should declare all components of dental composites to identify these substances that may result in allergic or undesirable side effects for patients and dental staff.

DEMOCOPHES España y su contribución a la armonización de la biovigilancia humana en Europa / DEMOCOPHES Spain and its contribution to the harmonization of european human biomonitoring

Objetivo: contribuir a la armonización europea de la biovigilancia en humanos (proyecto DEMOCOPHES) demostrando la utilidad de los estudios de biovigilancia para valorar la influencia de la dieta y los estilos de vida como vía de exposición a contaminantes ambientales. Métodos: se adaptó el protocolo europeo a las necesidades nacionales, siguiendo los controles de calidad definidos en él y sin comprometer la obtención de datos comparables entre los países participantes. Resultados: la adaptación nacional del protocolo europeo no presentó grandes dificultades y, salvo mínimas modificaciones, se respetó el diseño original del estudio. Participaron 134 parejas madre-hijo, seleccionados en un colegio de Añover de Tajo (Toledo) y tres colegios de Madrid. Los voluntarios donaron una muestra de pelo y de orina y contestaron a las preguntas del cuestionario epidemiológico. Se observaron diferencias significativas en la participación de los voluntarios en las dos localizaciones de muestreo. Discusión: la estandarización de todas las etapas de un estudio de biovigilancia en humanos es esencial para su desarrollo armonizado a escala internacional. Los resultados obtenidos han contribuido a la obtención de datos sobre exposición ambiental, por primera vez comparables en 17 países europeos, y han permitido observar diferencias relacionadas con la dieta y los hábitos de vida. Las experiencias y el material de trabajo desarrollado para el estudio piloto serán aplicables al diseño e implementación de futuros estudios de HBM (AU)

Objetive: contributing to demonstrate of the feasibility of a coordinated action on human biomonitoring in Europe (DEMOCOPHES project) and demonstrate the utility of HBM studies to assess the influence of diet and lifestyle in environmental exposures. Methods: the EU protocol was adapted to the national requirements. The quality controls defined herein were followed and special care was taken to ensure the comparability of the results among participating countries. Results: the protocol adaptation did not shown significant difficulties. Only minor changes were applied, so the original design of the study was respected. 134 mother-child pairs were selected in one school in Añover de Tajo (Toledo) and three schools in Madrid. All volunteers donated a urine and hair sample and complete the epidemiological questionnaire. Significant differences were found in the participation rates between the sampling locations. Discussion: standardization of all steps in a human biomonitoring study is essential for its harmonized development in Europe. The results has contributed to obtain for the first time comparable data about environmental exposure in the general population within 17 EU countries showing the differences associated with diet and lifestyles. The experiences and materials developed in the fieldwork could be applied to the design and implementation of HBM studies in the future (AU)

Toxicidad del Bisfenol A: Revisión / Toxicity of Bisphenol A: review

El Bisfenol A (BPA) es un compuesto químico muy utilizado en la industria. Se emplea como elemento y/o componente destinado a la fabricación de plásticos y resinas epoxi. Los plásticos y resinas producidas con BPA. se usa para la producción de recipientes con distintas aplicaciones, como puede ser; el envase de alimentos y bebidas, vajillas, papel térmico y dispositivos utilizados en el campo de la medicina, etc. Los seres humanos están expuestos a BPA de manera habitual, siendo la exposición a través de la dieta, (envases de comida y bebida) la fuente más importante de riesgo. Los materiales que permanecen en contacto con los alimentos son un punto clave de fuente contaminación, por ello deben estar evaluados y regulados para su utilización. El BPA se considera un disruptor endócrino con capacidad de alterar funciones y sistemas del organismo. En los últimos años, diversos estudios han relacionado la exposición a BPA con la aparición de efectos adversos para la salud. La EFSA, en su última opinión científica a cerca del BPA, concluye que, este compuesto no presenta riesgos para la salud de los expuestos y por tanto, actualmente en la Unión Europea, el BPA se considera un producto autorizado para la utilización como material destinado a entrar en contacto con los alimentos. Sin embargo, se continúa investigando sobre el BPA y sus posibles efectos adversos. La presente revisión recoge los estudios más recientes, 'in vitro' e 'in vivo' sobre la toxicidad del BPA, agrupados en las categorías, donde se ha visto implicación del BPA, en el estado de salud, siendo estas: proliferación celular y cáncer, alteraciones en el desarrollo y maduración celular, estrés oxidativo y daño en el material genético y afectación a nivel metabólico, reproductivo, cardiovascular y neuronal (AU)

Bisfenol A (BPA) is a chemical compound commonly used in industry. It is generally used as an element and/or component in the manufacturing of plastics and epoxy resins. These plastics and resins are used in the manufacture of containers with differentpurposes, for example; in the packaging of food and drinks, crockery, thermic paper, devices used in the medical field etc. Human beings are commonly exposed to BPA, being the diet (food and drink packaging) the highest exposure factor and therefore a key contamination spot. For this reason it is necessary that the usage of materials which are in contact with food is properly evaluated and regulated. BPA is considered a endocrine disruptor, with the capacity to alter functions and systems in the organism. Several studies have recently proposed a relation between the exposure to BPA and the appearance of adverse effects for the health. However, the EFSA recently concluded in their latest scientific opinion on the topic, that this compound does not imply any risk for the health of the exposed population. Therefore the EU considers BPA an authorised product to be used as material to enter in contact with food. However research on BPA and its potential negative effects is still ongoing. This review contains the latest 'in vitro' and 'in vivo' studies about BPA toxicity, these studies are grouped in the following categories (regarding different implications); cellular proliferation and cancer, alterations in development and cellular maturation, oxidative stress, damage to genetic material and finally alterations at a metabolic, reproductive, cardiovascular or neuronal level (AU)

Development of a composite resin disclosing agent based on the understanding of tooth staining mechanisms.

OBJECTIVES: To characterize the surface composition of dental enamel and composite resin, assess the ability of dyes with different affinities to stain these surfaces, and use this information to develop a disclosing agent that stains composite resin more than dental enamel. METHODS: One hundred and ten sound extracted teeth were collected and 60 discs of composite resin, 9 mm diameter and 3 mm thick, were prepared. X-ray photoelectron spectroscopy (XPS) was employed to determine the elemental composition on the different surfaces. A tooth shade spectrophotometer was used to assess the change in shade after staining the surfaces with different dyes. RESULTS: XPS analysis revealed that surfaces of both outer dental enamel and composite resin contained relatively high amounts of carbon, specifically hydrocarbons. Both dental enamel and composite surfaces were stainable with the hydrophobic dye (p<0.05); however, the composite resin was stained more than the dental enamel (p<0.05). CONCLUSIONS: The hydrophobic surface of dental enamel and composite resin might explain their high affinity to be stained by food and beverages containing hydrophobic molecules. The composite resin is more stainable by hydrophobic dyes than dental enamel. We used this information to develop an agent for disclosing composite resins that could be used to visualize composite resins that need to be removed. CLINICAL SIGNIFICANCE: Removal of composite resin can be problematic, time consuming and stressful to the dental practitioner. A composite disclosing agent would help the dental practitioner identify the composite resin and facilitate its removal without damaging the adjacent healthy tooth tissues.

Application of solid phase microextraction on dental composite resin analysis.

A direct immersion solid phase microextraction (DI-SPME) method was developed for the analysis of dentin monomers in saliva. Dentine monomers, such as triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA) and 2,2-bis-[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]-propane (Bis-GMA), have a high molecular weight and a low vapor pressure. The polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber with a medium polarity was employed for DI-SPME, and 215 nm of detection wavelength was found to be optimum in the chromatogram of HPLC measurement. The calibration range for DI-SPME was 0.30-300 µg/mL with correlation coefficients (r) greater than 0.998 for each analyte. The DI-SPME method achieved good accuracy (recovery 96.1-101.2%) and precision (2.30-8.15% CV) for both intra- and inter-day assays of quality control samples for three target compounds. Method validation was performed on standards dissolved in blank saliva, and there was no significant difference (p>0.2) between the DI-SPME method and the liquid injection method. However, the detection limit of DI-SPME was as low as 0.03, 0.27 and 0.06 µg/mL for TEGDMA, UDMA and Bis-GMA, respectively. Real sample analyses were performed on commercial dentin products after curing for the leaching measurement. In summary, DI-SPME is a more sensitive method that requires less sample pretreatment procedures to measure the resin materials leached in saliva.

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.

Release of monomers from four different composite materials after halogen and LED curing.

PURPOSE: To evaluate the release of monomers from four different composite materials (Ceram X, Filtek Supreme XT, Tetric Flow, Tetric EvoCeram), polymerized using either halogen or LED unit. METHODS: Ten specimens were made for each material/unit combination. Each specimen was stored in 1 ml 75% ethanol. The storage medium was renewed after 1, 7 and 28 days. Aliquots of this medium were analyzed by LC-MS/MS. RESULTS: The effect of the curing unit on monomers' release differed significantly among the materials (P < 0.0001). The amount of BisGMA and TEGDMA released from Ceram X was not influenced by the unit used (P > 0.05). Curing with LED reduced the amount of Bisphenol A released from Ceram X compared to halogen. For Filtek Supreme XT, the type of unit exerted a significant effect on the elution of BisGMA (P < or = 0.05). LED curing resulted in a higher release of TEGDMA and UDMA compared to halogen (P < or = 0.05). For Tetric Flow, LED curing resulted in lower monomer release (P < 0.0001). For Tetric EvoCeram, the amounts of BisGMA, UDMA and Bisphenol A were higher when polymerizing with LED compared to halogen. The release of substances was more material dependent and less influenced by the curing unit used.

Ternary phase diagram of model dentin adhesive exposed to over-wet environments.

When adhesives and/or composites are bonded to the tooth, water in the environment can interfere with proper interface formation. Formation of water blisters and phase separation at the adhesive/dentin interface have appeared as new types of bond defects. To better understand this problem, we determined the near-equilibrium partition of the hydrophobic/hydrophilic components when exposed to over-wet environments. Model methacrylate-based adhesives were mixed with different amounts of water to yield well-separated aqueous and resin phases. It was found that less than 0.1% BisGMA but nearly one-third of the HEMA diffused into the aqueous phase, leaving the remaining resin phase relatively hydrophobic. A partial phase diagram was created for the ternary BisGMA/HEMA/water system. All the experimental phase partitioning data were plotted, and the points lay on a binodal curve that separated the single-phase region from the two-phase region. We obtained the 3 tie lines by connecting the 2 points of each conjugate pair of the phase partitioning data from the 3 sets of tripartite mixtures. Information about solubility, water miscibility, distribution ratio, and phase partitioning behavior could be obtained quantitatively. This type of phase diagram will provide a more thorough understanding of current adhesive performance and elucidate directions for further improvement.

Monomer elution from nanohybrid and ormocer-based composites cured with different light sources.

OBJECTIVES: To study monomer elution from four resin-based composites (RBCs) cured with different light sources. METHODS: Twenty-eight premolars were randomly allocated to four groups. Standardized cavities were prepared and restored with a nanohybrid (Filtek Supreme XT or Tetric EvoCeram), an ormocer (Admira) or a microhybrid RBC (Filtek Z250) which served as control. Buccal restorations were cured with a halogen and oral restorations with an LED light-curing unit. Elution of diurethane dimethacrylate (UDMA), Bisphenol A diglycidylether methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) was analyzed using high-performance liquid chromatography (HPLC) 1h to 28 days post-immersion in 75% ethanol. Data were analyzed using multivariate and repeated measures analysis of variance (α = 0.05). RESULTS: The greatest elution of UDMA and BisGMA occurred from Tetric EvoCeram and the least from Filtek Z250 (p < 0.05). LED and halogen light-curing units gave similar results for all RBCs (p > 0.05) except Tetric EvoCeram which showed greater elution for the LED unit (p < 0.05). TEGDMA was below the limit of quantification. HEMA eluted in similar concentrations from Filtek Supreme and Tetric EvoCeram (p > 0.05). SIGNIFICANCE: The two nanohybrid RBCs eluted more cross-linking monomers than the ormocer and the control microhybrid RBC. Continuous elution over 28 days indicates that RBCs act as a chronic source of monomers in clinical conditions. Light source may affect monomer elution since differences were found for one out of four RBCs. Mathematical models for elution kinetics of UDMA and BisGMA indicated two elution mechanisms.

Degradation of polymeric restorative materials subjected to a high caries challenge.

OBJECTIVES: The aim of this study was to evaluate the degradation of different resin filling materials after a caries challenge, by high performance liquid chromatography (HPLC) and contact angle (θ) measurement. METHODS: Four different polymeric restorative materials (a resin composite, a polyacid-modified resin composite, an ormocer and a resin-modified glass ionomer cement) were tested. Five samples (30 mm × 6 mm × 2 mm) of each material were formed in a Teflon mold, following the manufacturer's instructions. After pH cycles, the solutions were injected in an HPLC. The θ was obtained, before and after pH cycle, by a goniometer at 60% air humidity and 25°C. A distilled water drop (0.006 ml) was put on the material surface, and after 6 min, 10 measures were obtained at 20s intervals. Each sample received 4 drops, one at a time, on different areas. RESULTS: HPLC results showed elution of byproducts in all materials. This was greater in the acid medium. Bis-GMA and TEGDMA were detected in TPH Spectrum and Definite residues. Analyses of the contact angle by ANOVA and Student-Neuman-Keuls's test showed that the surfaces of TPH Spectrum, Dyract AP and Definite were altered, except Vitremer (p<0.05). SIGNIFICANCE: All materials tested degraded on a caries simulated medium, suggesting that a great effort should be made to disseminate oral health information, since a high caries challenge environment (low pH) can lead to dental composite degradation, with potential toxic risks to patients.

Elution of residual monomers from dental composite materials.

AIM: This study was designed to determine the type and amount of the monomers leached from the different particle sizes of the composite materials. MATERIALS AND METHODS: Three different disk sizes (2, 4, 6 mm) prepared for each material group (Filtek Flow, Filtek A110, Filtek P60 and Filtek Supreme) were polymerised by LED and halogen light; the specimens were then placed in artificial saliva. The monomer release in 30 min and 24 hrs from the specimens was analyzed in HPLC calibrated for the monomer extracts before. RESULTS: TEGDMA release was detected in all material groups after 30 min and after 24 hrs. BisGMA and BisEMA were not determined in any groups and UDMA was detected only in Filtek Supreme. Significant differences in release of TEGDMA and UDMA were obtained between the different sizes of discs. Significantly high amount of TEGDMA and UDMA monomer release was obtained in LED than Halogen groups. Lower amount of monomer release was obtained in species of 30 min than 24 hrs. CONCLUSION: Data has revealed that the monomer release could be detected significantly high from the composite materials polymerized by a lower output curing light device; and higher elution of monomers was determined as the composite thickness has increased. Therefore, the clinical applications of composite materials and the type of curing units have very important effects on the success of restorations and in the decrease of potential side effects.

Use of micro-Raman spectroscopy to investigate hybrid layer quality in demineralized root dentine.

Treatment of early root caries using resin adhesives to stabilize demineralized dentine and deprive bacteria of nutrients is a recognized and conservative treatment option. Essential to its success is a stable resin-dentine interface, with effective infiltration of demineralized dentine and adequate resin curing. The objective of this study was therefore to examine degree of cure (DoC) and depth of penetration of dentine adhesives in demineralized dentine using micro-Raman spectroscopy. Three commercially available adhesives were applied essentially according to manufacturers' instructions to visibly wet demineralized dentine, with two coats of primer to reduce dilution. Specimens were sectioned perpendicular to the bonded interface and micro-Raman spectroscopy performed on the cross section. Molecules associated with the adhesive were detected to depths greater than 100 µm indicating a thicker hybrid layer than seen in sound dentine. The hybrid layer showed an increase in proportion of aliphatic C=C double bonds at the base of the hybrid layer, which may be a consequence of reduced DoC or phase separation. Micro-Raman spectra suggest deep zones contain an increased concentration of HEMA and a lower concentration of BisGMA, which is likely to be less stable and may contribute to early breakdown of the dentine adhesive interface.

Quantitative analysis of adhesive resin in the hybrid layer using Raman spectroscopy.

The objective was to determine absolute molar concentration of adhesive resin components in the hybrid layer by establishing methods based on Raman spectroscopy fundamentals. The hybrid layer was treated as a three-component system consisting of collagen and an adhesive resin containing two monomers. Adhesive standard specimens and Raman peak area ratios obtained with a 785 nm excitation wavelength were used to construct separate calibration curves for comonomer relative molar concentration and Bis-GMA absolute molar concentration. As collagen and water had no measurable peaks in the fingerprint region, a dilution coefficient K(j) was defined to describe their impact on Raman peak area and to calculate HEMA absolute molar concentration. Methodology was validated using an analogous system containing acetone/ethanol/water. The absolute molar concentration of Bis-GMA and HEMA decreased 87% and 83%, respectively, from the top quarter to the middle of the hybrid layer. Additionally, less Bis-GMA penetrated the hybrid layer than HEMA, as indicated by the approximately 20% decrease in comonomer molar concentration ratio between the adhesive resin layer and the top half of the hybrid layer. Lack of complete monomer infiltration will further challenge dentin-adhesive bond longevity. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Release of monomers from different core build-up materials.

OBJECTIVE: The aim of the present study was to evaluate and compare the elution of monomers from three different core build-up composite materials and correlate it with the degree of conversion. METHODS: Three different core build-up composite materials (a chemically cured, a photo-cured, and a dual-cured) were tested. Ten samples (diameter: 4.5 mm and thickness: 2 mm) of each material were fabricated to evaluate the release of monomers. The photo-cured samples were polymerized for 40s and the dual-cured samples for 20 s. The samples remained undisturbed for 10 min and then were stored in 1 ml of 75% ethanol at room temperature, and the storage medium was renewed after 24 h, 7 and 28 days. From the storage medium that was removed, samples were prepared and analyzed by LC-MS/MS. Additionally, four samples of each material were tested for the degree of conversion by using a FT-IR spectrometer. RESULTS: The three composite materials differed significantly concerning the elution of monomers (BisGMA: p<0.0001; TEGDMA: p<0.0001; and Bisphenol A: p<0.0001). A significantly higher amount of BisGMA and TEGDMA was released from the chemically cured composite compared to the other two materials. Between the photo-cured and the dual-cured material the latter eluted significantly higher amounts of BisGMA and TEGDMA. During the storage of the samples, the amounts of the eluted substances decreased. The degree of conversion of the chemically cured composite was significantly lower compared to the other two materials. SIGNIFICANCE: Using the present parameters, the photo-cured material released less monomer and therefore they might be less dangerous with respect to toxicological effects.