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D C Watts - One of the best experts on this subject based on the ideXlab platform.
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reduced polymerization stress of mapo containing resin composites with increased curing speed Degree of Conversion and mechanical properties
Dental Materials, 2014Co-Authors: William M Palin, Mohammed A Hadis, Julian Leprince, Gaetane Leloup, L Boland, Garry J P Fleming, G Krastl, D C WattsAbstract:Abstract Objectives The Degree and rate of photopolymerization in resin-based dental composites will significantly affect polymer network formation and resultant material properties that may determine their clinical success. This study investigates the mechanical properties, the generation of stress from polymerization, tooth cusp deflection and marginal integrity of experimental resin composites that contain different photoinitiators. Methods Experimental light-activated resin composites (60 vol% particulate filled in 50/50 mass% bis-GMA/TEGDMA) were formulated using a monoacylphosphine oxide (MAPO) photoinitiator and compared with a conventional camphoroquinone (CQ)-based system. Similar radiant exposure was used (18 J cm −2 ) for polymerization of each material although the curing protocol was varied (400 mW cm −2 for 45 s, 1500 mW cm −2 for 12 s and 3000 mW cm −2 for 6 s). Degree and rate of polymerization was calculated in real-time by near infrared spectroscopy and the generation of stress throughout polymerization measured using a cantilever beam method. Flexural strength and modulus were acquired by three-point bend tests. Standardized cavities in extract pre-molar teeth were restored with each material, the total cuspal deflection measured and post-placement marginal integrity between the tooth and restoration recorded. Results Generally, MAPO- exhibited a significantly higher Degree of Conversion (72 ± 0.8 to 82 ± 0.5%) compared with CQ-based materials (39 ± 0.7 to 65 ± 1.6%) regardless of curing protocol ( p 50% Conversion. Higher irradiance polymerization had a significant deleterious effect on the mechanical properties of CQ-based materials ( p −1 for 6 s (10.1 ± 3.5 and 9.0 ± 1.5 μm). A significant decrease in marginal integrity was observed for CQ-based RBCs cured at high irradiance for short exposure time compared with that of the MAPO-based RBC cured using a similar protocol ( p = 0.037). Significance Polymer network formation dictates the final properties of the set composite and the use MAPO photoinitiators may provide an effective restorative material that exhibits higher curing speeds, increased Degree of Conversion, strength and modulus without compromise in terms of polymerization stress and marginal integrity between tooth and restoration.
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effects of monomer ratios and highly radiopaque fillers on Degree of Conversion and shrinkage strain of dental resin composites
Dental Materials, 2009Co-Authors: Amel Amirouchekorichi, Mohamed Mouzali, D C WattsAbstract:Abstract Objectives The Degree of Conversion (DC) and polymerization shrinkage of resin composites are closely related manifestations of the same process. Ideal dental composite would show an optimal Degree of Conversion and minimal polymerization shrinkage. These seem to be antagonistic goals, as an increase in monomer Conversion leads to a high polymerization shrinkage. This paper aims to determine the effect of opaque mineral fillers and monomer ratios on the DC and the shrinkage-strain of experimental composites based on (BisGMA/TEGDMA) monomers (traditionally used monomers). A relationship between the shrinkage-strain and the Degree of Conversion values was also investigated. The radiopacity of these experimental composites has been investigated in a previous paper. Methods Experimental resin composites were prepared by mixing different monomer ratios of (BisGMA/TEGDMA) with Camphoroquinone and dimethyl aminoethyl methacrylate (DMAEMA) as photo-initiator system. Five different radiopacifying filler agents: La2O3, BaO, BaSO4, SrO and ZrO2 at various volume fractions ranging from 0 to 80 wt.% were added to the mixture. The Degree of Conversion of experimental composites containing different opaque fillers contents was measured using FTIR/ATR spectroscopy. The shrinkage-strain of specimens, photopolymerized at circa 500 mW/cm2, was measured using the bonded-disk technique at room temperature with respect to time. Results The result revealed that the DC and the shrinkage-strain decrease slightly with the increasing of opaque fillers loadings, but this decrease is not significant. However, these two properties are closely related to the monomer concentration of the organic matrix. The results have also showed a linear correlation between the shrinkage-strain and DC of experimental composites investigated. Significance The nature and the volume effects of the opaque fillers on the DC and shrinkage of the experimental composites investigated were not significant. However, this study has confirmed the importance of viscosity in the system and shrinkage behavior of dimethacrylate monomers studied. Then we confirmed that direct relationships linked the shrinkage and the DC of filled dental resin composites.
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Degree of Conversion of bis acrylic based provisional crown and fixed partial denture materials
The Journal of Korean Academy of Prosthodontics, 2008Co-Authors: D C WattsAbstract:. BisGMA has a functional group which does not participate in polymerization. The aromatic double bond of this group (phenyl group) has an absorbance at 1608 cm-1 . This absorbance remains constant before and after polymerization. This method is based on comparing the intensities of the absorbance of carbon-carbon double bonds in methacrylate group before and after polymerization. In aromatic moieties, the absorbance of aromatic double bonds can be used as an internal standard. The purpose of this study was to measure the Degree of Conversion of three bis-acrylic based provisional crown and fixed partial denture materials by using an infrared spectroscopic method. The null hypothesis to be tested is that there is no significant difference in the Degree of Conversion among bis-acrylic based provisional crown and fixed partial denture materials.
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light intensity effects on resin composite Degree of Conversion and shrinkage strain
Dental Materials, 2000Co-Authors: Nick Silikas, George Eliades, D C WattsAbstract:Abstract Objective: The aim of this study was to investigate the relationship between the Degree of Conversion (DC) and shrinkage strain values of two representative resin-composites when irradiated by two light intensity levels, for different time periods. Methods: The DC of Z100 and Tetric Ceram was measured by FTIR spectroscopy immediately post-cure and shrinkage strain values were obtained continuously for 30 min from photoinitiation with the bonded-disk technique. All samples were photopolymerized at an initial temperature of 23°C with the Elipar Highlight unit under the following modes of variable light intensity (I) 40 s at 750 mW/cm 2 ; (II) a two-step ‘soft-start’ irradiation mode of 10 s at 200 mW/cm 2 plus 30 s at 750 mW/cm 2 ; (III) 40 s at 200 mW/cm 2 ; and (IV) 10 s at 200 mW/cm 2 . Temperature effects of the light and curing exotherm were not eliminated. Results: Mode II of irradiation did not reduce the DC for each material, relative to the values obtained with mode I ( p >0.05). The corresponding shrinkage strain values after 30 min were also not significantly different ( p >0.05). However, the effects of reduced light intensity levels for 10 s and 40 s (modes III and IV), were in agreement with previous findings implying reduced shrinkage strain levels. For both resin composites, data from all curing times and light-intensities gave a linear regression relationship (with r 2 >0.99) between the bonded-disk shrinkage strain versus DC values. Significance: For the materials and light-intensities studied, the correlation between DC and shrinkage strain values means that some reductions in the problems of shrinkage may be achieved by an acceptable reduction in DC. However, this must also be consistent with generating adequate curing performance in the resin-network. Nevertheless, DC is not the exclusive parameter describing network character and a fuller understanding of the latter is an important research goal.
Roberto Ruggiero Braga - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of bulk fill composites Degree of Conversion post gel shrinkage and cytotoxicity
Brazilian Oral Research, 2018Co-Authors: Flavia Goncalves, Roberto Ruggiero Braga, Carlos Eduardo Francci, L M P Campos, Pamela Adeline Marques, Ezequias Costa Rodriguesjunior, Fabricia Viana Costa, Leticia Cristina Cidreira BoaroAbstract:Bulk-fill composites are claimed to be restorative materials used in deep preparations and effectively photoactivated in layers up to 4 mm. The aim of the present study was to evaluate the Degree of Conversion, post-gel volumetric shrinkage, and cytotoxicity of six bulk-fill and two conventional composites. Degree of Conversion was determined by FTIR spectroscopy; post-gel volumetric shrinkage was determined using the strain gauge method; and cytotoxicity in human fibroblasts was evaluated indirectly by the MTT assay. Data were subjected to one-way ANOVA/Tukey's test (α = 0.05). All materials, including bulk-fill and conventional composites, were classified as non-toxic, with cell viability higher than 70%. Bulk-fill composites exhibited volumetric shrinkage similar to or lower (1.4 to 0.4%) than that of conventional composites (1.7-2.1%). However, only four of the bulk-fill composites were able to sustain a homogeneous Conversion at the 4-mm depth. Despite their non-toxicity and shrinkage similar to that of conventional materials, not all commercial bulk-fill materials were able to maintain a Conversion as high as 80% of the superficial layer, at the 4-mm depth, indicating some failure in the bulk-fill design of some commercial brands. Therefore, the use of bulk-fill materials in dental practice is advantageous, but special attention should be given to the selection and correct use of the materials.
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evaluation of flexural modulus flexural strength and Degree of Conversion in bisgma tegdma resin filled with montmorillonite nanoparticles
Journal of Composite Materials, 2017Co-Authors: L M P Campos, Roberto Ruggiero Braga, Leticia Cristina Cidreira Boaro, Tamiris M R Santos, Pamela Adeline Marques, Sonia Regina Yokomizo De Almeida, D F ParraAbstract:This study had as its main objective to evaluate the flexural properties (strength and modulus) and Degree of Conversion of a dimethacrylate resin containing different amounts of nanoparticulated clay Montomorillonite (MMT) as filler. A series of composites containing similar amounts (in volume) of barium glass particles was also tested as control data. Eight formulations with polymeric matrix-based BisGMA/TEGDMA (Bisphenol A Bis(2-hydroxy-3 methacryloxypropyl)Ether/Triethyleneglycol Dimethacrylate), four added with MMT and four added with barium glass in the volume concentration of 20, 30, 40 and 50 vol% were studied. The Degree of Conversion was determined using near-IR spectroscopy. Elastic modulus and flexural strength were determined by the three-point bending test. The dispersion of MMT nanoparticles was determined by means of X-ray diffraction and transmission electron microscopy analysis. The fillers montomorillonite and barium glass interacted with polymer matrix-based BisGMA/TEGDMA in a distinct...
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Correlation between clinical performance and Degree of Conversion of resin cements: a literature review
Journal of applied oral science : revista FOB, 2015Co-Authors: Grace M. De Souza, Roberto Ruggiero Braga, Paulo Francisco Cesar, Guilherme Carpena LopesAbstract:Resin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high Degree of Conversion (DC) under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the Degree of Conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used.
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effect of temperature on composite polymerization stress and Degree of Conversion
Dental Materials, 2014Co-Authors: Fernanda Calabro Calheiros, Frederick A Rueggeberg, Marcia Daronch, Roberto Ruggiero BragaAbstract:Abstract Objective To test the following hypotheses: (1) Degree of Conversion (DC) and polymerization stress (PS) increase with composite temperature (2) reduced light-exposure applied to pre-heated composites produces similar Conversion as room temperature with decreased PS. Methods Composite specimens (diameter: 5 mm, height: 2 mm) were tested isothermally at 22 °C (control), 40 °C, and 60 °C using light-exposures of 5 or 20 s (control). DC was accessed 5 min after light initiation by FTIR at the specimen bottom surface. Maximum and final PS were determined, also isothermally, for 5 min on a universal testing machine. Non-isothermal stress was also measured with composite maintained at 22 °C or 60 °C, and irradiated for 20 s at 30 °C. Data were analyzed using two-way ANOVA/Tukey and Student's t -test ( α = 5%). Results Both DC and isothermal maximum stress increased with temperature ( p p p Clinical significance : Increasing composite temperature allows for reduced exposure duration and lower polymerization stress (both maximum and final) while maintaining or increasing Degree of Conversion.
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monomers used in resin composites Degree of Conversion mechanical properties and water sorption solubility
Brazilian Dental Journal, 2012Co-Authors: V E S Gajewski, Carmem S Pfeifer, N R G Froessalgado, Leticia Cristina Cidreira Boaro, Roberto Ruggiero BragaAbstract:The organic phase of resin composites is constituted by dimethacrylate resins, the most common monomers being the bisphenol A diglycidildimethacrylate (BisGMA), its ethoxylated version (BisEMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA). This study compared the homopolymers formed from the monomers used in restorative dental composites in terms of their Degree of Conversion (DC) and reaction kinetics (by near infra-red spectroscopy, n=3), mechanical properties (flexural modulus and strength in three point-bending, FM and FS, respectively, n=15), water sorption and solubility (WS and SL, respectively - ISO 4049, n=5). Materials were made photopolymerizable by the addition of camphoroquinone/dimethylamine ethyl methacrylate. TEGDMA showed the highest DC, followed by BisEMA, UDMA and BisGMA, both at 10 min and at 24h (p 0.001). For FS, UDMA presented the highest value (p 0.001). BisGMA showed the highest WS, and TEGDMA and BisEMA the lowest. UDMA was statistically similar to all (H0=16.074, p<0.001). TEGDMA presented the highest SL, followed by UDMA, BisGMA and BisEMA (p<0.001). The tested homopolymers presented different behaviors in terms of polymerization kinetics, flexural properties, water sorption and solubility. Therefore, the use of copolymers is justified in order to obtain high DC and mechanical properties, as well as good resistance to water degradation.
Airton Abrahao Martin - One of the best experts on this subject based on the ideXlab platform.
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does an additional uv led improve the Degree of Conversion and knoop hardness of light shade composite resins
European Journal of Dentistry, 2012Co-Authors: Maria Cecilia Caldas Giorgi, Priscila Christiane Suzy Liporoni, Luis Eduardo Silva Soares, Airton Abrahao Martin, Flavio Henrique Baggio Aguiar, Luis Alexandre Maffei Sartini PaulilloAbstract:Objective: The purpose of this study was to evaluate the Degree of Conversion (DC) using FT-Raman spectroscopy and the Knoop hardness (KHN) of composites cured by second and third-generation LED light curing-units (LCU), Radii Cal and Ultralume 5.
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influence of the photoinitiator system and light photoactivation units on the Degree of Conversion of dental composites
Brazilian Oral Research, 2010Co-Authors: Isabel Cristina Celerino De Moraes Porto, Airton Abrahao Martin, Luis Eduardo Silva Soares, Vanessa Cavalli, Priscila Christiane Suzy LiporoniAbstract:The aim of this study was to observe the influence of two light polymerization units (LED or halogen light) on the Degree of Conversion (DC) of three dental composites with lighter shades and a different photoinitiator system. The top (T) and bottom (B) surfaces of 60 discs of composite resin (Filtek™ Supreme, Filtek™ Z250, Tetric™ Ceram Bleach) cured either by LED or by halogen lamp (HL) were studied using an FT-Raman spectrometer. The Degree of Conversion (DC) was evaluated by following the changes in the intensity of the methacrylate C=C stretching mode at 1640 cm-1. The calculated DC ranged from 54.2% (B) to 73.4% (T) and from 60.2% (B) to 76.6% (T) for the LED and HL, respectively. LED and halogen devices were able to produce an adequate DC for all the resins tested.
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influence of fiber post translucency on the Degree of Conversion of a dual cured resin cement
Journal of Endodontics, 2007Co-Authors: Andre Luis Faria E Silva, Luis Eduardo Silva Soares, Airton Abrahao Martin, Vanessa Gallego Arias, Luis Roberto Marcondes MartinsAbstract:This study evaluated the Degree of Conversion of one dual-cured resin cement when used to lute fiber posts with different translucencies. To measure the Degree of Conversion, polyvinylsiloxane molds were prepared to simulate root canals. The posts, Aestheti-Post or Light-Post, were cemented in these molds and, after photoactivation, were removed to obtain the resin cement spectrum by FT-Raman spectroscopy. Spectra were acquired at three depths: superficial, medium, and deep. For Light-Post, the resin cement at deep depth showed the lowest Degree of Conversion and no significant difference in Degree of Conversion was found between the other depths. For Aestheti-Post, the superficial depth presented a higher Degree of Conversion values than those in the medium and deep depths, which were not significantly different from each other. Light-Post exhibited a higher Degree of Conversion than that of Aestheti-Post only at medium depth. Light-Post effectiveness regarding the Degree of Conversion is dependent on the depth.
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the effect of soft start polymerization by second generation leds on the Degree of Conversion of resin composite
Operative Dentistry, 2007Co-Authors: Luis Eduardo Silva Soares, Priscila Christiane Suzy Liporoni, Airton Abrahao MartinAbstract:Clinical Relevance Photo-polymerization using second generation LED and halogen light in the soft-start mode of curing was able to produce an adequate Degree of Conversion in resin composites. The ...
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The effect of soft-start polymerization by second generation LEDs on the Degree of Conversion of resin composite.
Operative Dentistry, 2007Co-Authors: Luis Eduardo Silva Soares, Priscila Christiane Suzy Liporoni, Airton Abrahao MartinAbstract:Clinical Relevance Photo-polymerization using second generation LED and halogen light in the soft-start mode of curing was able to produce an adequate Degree of Conversion in resin composites. The lower Degree of Conversion produced by low power LED in the soft-start mode could lead to restoration failure, degradation of the organic matrix and recurrent caries.
David H Pashley - One of the best experts on this subject based on the ideXlab platform.
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effect of air drying on the solvent evaporation Degree of Conversion and water sorption solubility of dental adhesive models
Journal of Materials Science: Materials in Medicine, 2012Co-Authors: David H Pashley, M Bail, J Malacarnezanon, S M A Silva, A Anauatenetto, Fabio D Nascimento, Ricardo Amore, Hugo Roberto Lewgoy, M R O CarrilhoAbstract:This study evaluated protocols to eliminate acetone from dental adhesives and their effect on the kinetic of water sorption and percent of Conversion of these adhesives. Experimental methacrylate-based adhesives with increasing hydrophilicity (R2, R3, R5) were used as reference materials. Primer-like solutions were prepared by addition of 50 wt% acetone. Acetone elimination was measured gravimetrically before and after: a spontaneous evaporation, an application of air-drying at room temperature or application of 40°C air-drying. Protocols were performed from 15 to 60 s. Specimens of adhesive/acetone mixtures were photo-activated and tested for Degree of Conversion, water sorption and solubility. Data were analyzed by ANOVA and Bonferroni’s tests (α = 0.05). Complete acetone elimination was never achieved, but it was significantly greater after the 40°C air-drying application. Higher acetone elimination was observed for the least hydrophilic adhesive. Longer periods for acetone evaporation and heated air-stream can optimize polymerization and reduce the water sorption/solubility of adhesive system models.
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influence of different initiators on the Degree of Conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content
Dental Materials, 2010Co-Authors: M Cadenaro, Francesca Antoniolli, Franklin R Tay, David H Pashley, Barbara Codan, Kelli A Agee, E Dorigo, Lorenzo BreschiAbstract:Objectives The aim of this study was to compare the curing reaction of five experimental adhesive blends containing different photo-initiating systems. The hypothesis tested was that Degree of Conversion (DC) of resin blends is affected by resin type, solvent content and photo-initiating system.
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effects of residual ethanol on the rate and Degree of Conversion of five experimental resins
Dental Materials, 2009Co-Authors: Milena Cadenaro, Frederick A Rueggeberg, Lorenzo Breschi, Franklin R Tay, Roberto Di Lenarda, Kelli A Agee, Michael Suchko, Evan Grodin, David H PashleyAbstract:Abstract Objectives This study examined the extent of ethanol retention in five comonomer blends of experimental methacrylate-based dental adhesives, containing (10, 20, or 30 wt.%) ethanol, after solvent evaporation, as well as observing the effect of residual ethanol and exposure duration on Degree of Conversion (DC). The null hypothesis that was tested was that residual, unevaporated ethanol has no effect on the rate or extent of DC of polymerized adhesive resins. Methods A known mass of each mixture was placed in glass wells and evaporated for 60 s. The mass of the mixtures before and after evaporation was measured, allowing calculation of the gravimetric ethanol loss/retention. Results The concentration of retained ethanol increased significantly with ethanol concentration ( p p Significance Since 10 and 20 wt.% ethanol–resin blends increased the DC of solvated resins by 30–45% over neat resins, the test null hypothesis is rejected. Even with prolonged evaporation, 4–9% residual ethanol concentration can remain in 90/10 (wt./wt.) comonomer–ethanol mixtures. This is thought to be because comonomers lower the vapor pressure of ethanol. This amount of residual ethanol facilitates DC but lowers the rate of polymerization.
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Degree of Conversion of resin blends in relation to ethanol content and hydrophilicity
Dental Materials, 2008Co-Authors: M Cadenaro, Lorenzo Breschi, Francesca Antoniolli, Chiara Ottavia Navarra, Annalisa Mazzoni, Franklin R Tay, Roberto Di Lenarda, David H PashleyAbstract:Abstract Objectives To evaluate the Degree of Conversion of five experimental adhesive systems in relation to their hydrophilicity. The resin blends ranged from hydrophobic to hydrophilic and were tested as neat bonding agents, or solvated with increasing percentages of ethanol. The hypothesis tested was that extent of polymerization of resin blends is affected by resin hydrophilicity, solvent concentrations or time of polymerization. Methods Five light-curing versions of neat experimental resin blends were submitted to investigation: (1) 70% E-BisADM, 28.75% TEGDMA; (2) 70% BisGMA, 28.7% TEGDMA; (3) 70% BisGMA, 28.7% HEMA; (4) 40% BisGMA, 30% TCDM, and 28.75% TEGDMA; (5) 40% BisGMA, 30% BisMP, and 28.75% HEMA. All blends included 1% EDMAB and 0.25% CQ. Ethanol in different weight percentages (A: 0%, B: 30%, C: 50%, D: 70% and E: 90%) was added to these resin blends simulating different formulation of adhesives. A differential scanning calorimeter was used to measure the Degree of Conversion of resin blends as a function of resin hydrophilicity, solvent concentration and time of curing. Data were analyzed with three-way ANOVA and Tukey's post hoc test. Results Exotherms showed that Degree of Conversion was influenced by the hydrophilicity of the blends resin ( p p p Significance This study supports the hypothesis that high ethanol percentages (>50 mass%) may compromise extent of polymerization kinetics of dental adhesives.
Lorenzo Breschi - One of the best experts on this subject based on the ideXlab platform.
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influence of different initiators on the Degree of Conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content
Dental Materials, 2010Co-Authors: M Cadenaro, Francesca Antoniolli, Franklin R Tay, David H Pashley, Barbara Codan, Kelli A Agee, E Dorigo, Lorenzo BreschiAbstract:Objectives The aim of this study was to compare the curing reaction of five experimental adhesive blends containing different photo-initiating systems. The hypothesis tested was that Degree of Conversion (DC) of resin blends is affected by resin type, solvent content and photo-initiating system.
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Degree of Conversion of filtek silorane adhesive system and clearfil se bond within the hybrid and adhesive layer an in situ raman analysis
Dental Materials, 2009Co-Authors: Chiara Ottavia Navarra, Francesca Antoniolli, Roberto Di Lenarda, Milena Cadenaro, Steven R Armstrong, Julie L P Jessop, Valter Sergo, Lorenzo BreschiAbstract:Abstract Objectives To examine the Degree of Conversion (DC) of the adhesive interfaces created by Filtek Silorane Adhesive and Clearfil SE Bond using micro-Raman spectroscopy. Methods The adhesives were applied on human dentin in accordance with manufacturer's instructions. Specimens were cut to expose the bonded interfaces to the micro-Raman beam (Ranishaw InVia; laser wl 785 nm). Raman spectra were collected along the dentin/self-etching primer/adhesive interface at 1 μm intervals. The relative intensities of bands associated with mineral (P–O functional group at 960 cm −1 ) and adhesive (C–C–O group at 605 cm −1 ) components within the bonded interface were used to detect monomer penetration into the dentin matrix and to calculate the Degree of Conversion (C C at 1640 cm −1 as reaction peak, C–C–O at 605 cm −1 as reference peak). Data were statistically analyzed with two-way ANOVA. Results DC of Filtek Silorane Adhesive was 69 ± 7% in the adhesive layer, increasing ( p p p Significance As high DC is a fundamental pre-requisite for the stability of the bond over time, this study supports the hypothesis that optimal stability of Filtek Silorane Adhesive can be obtained. However, further research is needed to investigate the mechanical properties of the hybrid layer created by Filtek Silorane Adhesive and its long-term stability.
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Degree of Conversion and interfacial nanoleakage expression of three one step self etch adhesives
European Journal of Oral Sciences, 2009Co-Authors: Chiara Ottavia Navarra, M Cadenaro, Annalisa Mazzoni, Barbara Codan, E Dorigo, Valter Sergo, Lorenzo BreschiAbstract:Suboptimally polymerized monomers may be responsible for the reduced material properties of simplified adhesives and their inherent bonded interface instability. This study was performed to determine the Degree of cure within the hybrid layers produced by three one-step self-etch adhesives in situ using Raman microspectroscopy and to investigate nanoleakage expression. Dentin disks were bonded with AdheSE One, Adper Prompt L-Pop, or iBond. Composite layers of 2-mm thickness were built up in bulk on the polymerized adhesive surfaces and then the adhesive-dentin interfaces were exposed to a micro-Raman beam. Adhesive penetration was calculated using the relative intensities of bands associated with mineral and adhesive, and the Degree of Conversion (DC) was evaluated. Interfacial nanoleakage expression was evaluated on the same specimens. The DC values for the tested adhesives were found to increase in the following order: AdheSE One (48 +/- 16%) < Adper Prompt L-Pop (83 +/- 2%) = iBond (90 +/- 6%; P < 0.05). AdheSE One showed greater nanoleakage expression than iBond or Adper Prompt L-Pop. Increased nanoleakage expression was associated with AdheSE One that showed the lowest DC. This suggests that a low DC may affect the quality and the long-term stability of the adhesive interface owing to the elution of unreacted monomers forming a porous and highly permeable hybrid layer.
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effects of residual ethanol on the rate and Degree of Conversion of five experimental resins
Dental Materials, 2009Co-Authors: Milena Cadenaro, Frederick A Rueggeberg, Lorenzo Breschi, Franklin R Tay, Roberto Di Lenarda, Kelli A Agee, Michael Suchko, Evan Grodin, David H PashleyAbstract:Abstract Objectives This study examined the extent of ethanol retention in five comonomer blends of experimental methacrylate-based dental adhesives, containing (10, 20, or 30 wt.%) ethanol, after solvent evaporation, as well as observing the effect of residual ethanol and exposure duration on Degree of Conversion (DC). The null hypothesis that was tested was that residual, unevaporated ethanol has no effect on the rate or extent of DC of polymerized adhesive resins. Methods A known mass of each mixture was placed in glass wells and evaporated for 60 s. The mass of the mixtures before and after evaporation was measured, allowing calculation of the gravimetric ethanol loss/retention. Results The concentration of retained ethanol increased significantly with ethanol concentration ( p p Significance Since 10 and 20 wt.% ethanol–resin blends increased the DC of solvated resins by 30–45% over neat resins, the test null hypothesis is rejected. Even with prolonged evaporation, 4–9% residual ethanol concentration can remain in 90/10 (wt./wt.) comonomer–ethanol mixtures. This is thought to be because comonomers lower the vapor pressure of ethanol. This amount of residual ethanol facilitates DC but lowers the rate of polymerization.
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Degree of Conversion of resin blends in relation to ethanol content and hydrophilicity
Dental Materials, 2008Co-Authors: M Cadenaro, Lorenzo Breschi, Francesca Antoniolli, Chiara Ottavia Navarra, Annalisa Mazzoni, Franklin R Tay, Roberto Di Lenarda, David H PashleyAbstract:Abstract Objectives To evaluate the Degree of Conversion of five experimental adhesive systems in relation to their hydrophilicity. The resin blends ranged from hydrophobic to hydrophilic and were tested as neat bonding agents, or solvated with increasing percentages of ethanol. The hypothesis tested was that extent of polymerization of resin blends is affected by resin hydrophilicity, solvent concentrations or time of polymerization. Methods Five light-curing versions of neat experimental resin blends were submitted to investigation: (1) 70% E-BisADM, 28.75% TEGDMA; (2) 70% BisGMA, 28.7% TEGDMA; (3) 70% BisGMA, 28.7% HEMA; (4) 40% BisGMA, 30% TCDM, and 28.75% TEGDMA; (5) 40% BisGMA, 30% BisMP, and 28.75% HEMA. All blends included 1% EDMAB and 0.25% CQ. Ethanol in different weight percentages (A: 0%, B: 30%, C: 50%, D: 70% and E: 90%) was added to these resin blends simulating different formulation of adhesives. A differential scanning calorimeter was used to measure the Degree of Conversion of resin blends as a function of resin hydrophilicity, solvent concentration and time of curing. Data were analyzed with three-way ANOVA and Tukey's post hoc test. Results Exotherms showed that Degree of Conversion was influenced by the hydrophilicity of the blends resin ( p p p Significance This study supports the hypothesis that high ethanol percentages (>50 mass%) may compromise extent of polymerization kinetics of dental adhesives.