RESUMEN
This study evaluated the biological behavior of the coffee compounds Trigonelline (T), chlorogenic acid (C), and nicotinic acid (N), correlating with their release from a resin matrix. Minimum inhibitory concentration (MIC) was evaluated against Streptococcus mutans UA159, and cytotoxicity was assessed by methyl tetrazolium salt on OD-21 cells. Resin matrices (bisphenol A-glycidyl-dimethacrylate/triethylene glycol-dimethacrylate 70/30 wt%, camphorquinone/ethyl 4-dimethyl aminobenzoate 0.5/1 wt%) were doped with coffee compounds in different concentrations (10/20/30/40/50 wt%), performing 15 groups (T10-T50, C10-C50, N10-N50), and a control group with no coffee compound. Degree of conversion (DC%) was analyzed by Fourier transform infrared spectroscopy. Antimicrobial properties were evaluated by bioluminescence (Luciferase assay). The release from loaded matrices was analyzed over time (24 hr, 6, 14, 21 and 28 days), using high-performance liquid chromatography (HPLC). Data were submitted to ANOVA/Tukey's test (α = 0.05). MIC for T and C was 6 mg/ml, and 4 mg/ml for N. None of them were cytotoxic. Only T50 and C50 showed lower DC% than control (α < 0.05). Some groups (T30/T40/T50/C40/C50/N50) were strongly antimicrobial, reducing bacterial activity approximately five times compared to control (α < 0.05). For T30, T40, T50, C40, and C50, the HPLC showed a release above or closer to MIC values mainly in 24 hr, but for N50, up to 28 days. In conclusion, the coffee compounds presented antimicrobial activity, depending on their concentration when added in resin matrices, being found a correlation with their release.
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Alcaloides , Antiinfecciosos , Ácido Clorogénico , Café/química , Niacina , Streptococcus mutans/crecimiento & desarrollo , Alcaloides/química , Alcaloides/farmacología , Antiinfecciosos/química , Antiinfecciosos/farmacología , Ácido Clorogénico/química , Ácido Clorogénico/farmacología , Resinas Compuestas/química , Resinas Compuestas/farmacología , Niacina/química , Niacina/farmacologíaRESUMEN
Thio-urethane oligomers improve conversion and mechanical properties of resin cements. The objective of this study was to evaluate the effect of resin cements formulated with thio-urethane (TU) oligomers on microtensile bond strength (µTBS) of ceramics to composites subjected to thermal/mechanical cycling. Methods: BisGMA/UDMA/TEGDMA (50/30/20 wt%) containg 0 (control, EC) or 20 wt% aliphatic or aromatic thiourethane (HDDI and BDI, respectively) were mixed with CQ/amine (0.2/0.8 wt%) and 25 wt% 0.7um Ba glass. Rely X Ultimate (RU-3M ESPE) was used as the commercial control. The cements were sandwiched between ceramic (IPS e.max Press) and resin composite blocks (Filtek Supreme, 3 M-ESPE). Eight bonded blocks were produced per experimental group. Prior to bonding, ceramic surfaces were etched (20 s - 10% HF) and silanized. Composite surfaces were treated with Single Bond Universal (3 M ESPE). Specimens were stored for 24 h in distilled water at 37 °C, and then either tested immediately, or subjected to thermal (10,000, 5 °C and 55 °C) or mechanical cycling (300,000 cycles). Sticks (1 mm2, average of 25 sticks per block) were cut and tested for µTBS (1.0 mm/min). Data were analyzed with two-way ANOVA/Tukey's test (α = 5%). Fracture surfaces were analyzed to determine failure modes. Results: The µTBS for HDDI and RU was significantly higher than BDI and EC cements. BDI led to significantly higher µTBS than EC after 24 h, Tc and Mf. µTBS decreased significantly after thermal/mechanical cycling for all groups. Failure modes were predominantly adhesive or mixed. Significance: The use of selected thio-urethane oligomers was able to increase the µTBS of composite-cement-ceramic specimens. Tc and Mf reduced µTBS for all resins cements.
RESUMEN
The aim of this in vitro study was to synthesize three new methacrylate monomers based on the modification of saccharides structures (glucose-Gluc, sucrose-Sucr and chitosan-Chit) with glycidyl methacrylate, and to use them in the composition of dental adhesives. Three methacrylate saccharide monomers were synthesized and characterized by mid-IR, 1H and 13C NMR, antioxidant activity and cytotoxic effect. Monomers included: one monosaccharide - Gluc-MA; one disaccharide - Sucr-MA; and one polysaccharide - Chit-MA. Primers containing HEMA, methacrylate saccharide monomers at concentrations of 0 (control), 1, 2 or 4 wt%, 60 wt% ethanol aqueous solution (pH3.0) and initiator system were formulated. Primers were used in conjunction with a bond step and composite paste to restore caries-free third molars, and dentin bond strength (24 hours and 6 month of storage in water), and antimicrobial activity (Alamar Blue test) were tested. Degree of conversion (DC) and maximum rate of polymerization (Rpmax) of the primers themselves were also analyzed. The mid-IR, 1H and 13C spectrum confirmed the presence of vinyl group on the structure of saccharides. Chit-MA showed low antioxidant activity and did not present a cytotoxic effect. Gluc-MA and Sucr-MA possess antioxidant and cytotoxic activity, concentration dependent. In the presence of methacrylate saccharide monomers, the primers showed DC comparable to the control group, except Gluc-MA4%, Sucr-MA4% and Chit-MA1%, which showed a range of 64.6 from 58.5 %DC. Rpmax was not statistically different for all the groups (p = 0.01). The bond strength of Sucr-MA1% increased from 25.7 (±2.8) to 40.6 (±5.3) MPa after 6 months of storage. All the synthesized monomers showed some antimicrobial activity after polymerization. Gluc-MA and Chit-MA 4% and Sucr-MA 1, 2 and 4% led to decrease bacterial metabolism. Sucr-MA 1% showed better results regarding the decrease in bacterial metabolism and increasing the bond strength after 6 months of storage.
RESUMEN
OBJECTIVE: This study determined the volumetric shrinkage, degree of conversion, sorption, solubility, and flexure properties (before and after aging) of commercial dental composites identified as "low shrinkage". METHODS: Six Bis-GMA-based composites (Point 4, ELS, Filtek Supreme, Aelite LS Posterior, Filtek Z250 and Heliomolar), a silorane-based (Filtek LS) and a dimer dicarbamate dimethacrylate-based composite (N'Durance) were studied. Total shrinkage was measured in a mercury dilatometer (n=3). Elastic modulus and flexural strength was determined by the three point bending test before and after 4 months aging in 75% ethanol solution (n=10). Sorption and solubility in water was assessed according to ISO 4049. Additionally, composite degree of conversion was determined using near-IR spectroscopy (n=3). Data were analysed using one-way/two-way ANOVA or Kruskal-Wallis, and Tukey's test. Student's t-test was used to compare storage periods (α=0.05). RESULTS: The volumetric shrinkage values ranged between 1.5% (Filtek LS) and 3.4% (Point 4). The materials presented different behaviors regarding aging in ethanol, as evidenced by the large range in values of percentage reduction for elastic modulus (26-75%) and flexural strength (25-86%). Sorption values ranged from 8.2µg/mm(3) (Aelite LS Posterior) to 38.2µg/mm(3) (Point 4). Solubility values ranged from -1.5µg/mm(3) (Filtek LS) to 5.7µg/mm(3) (Aelite LS Posterior). The degree of conversion values at 10min ranged between 28% (Filtek LS) and 73% (Point 4). At 72h after curing the values ranged between 39% (Filtek LS) and 83% (Point 4). SIGNIFICANCE: Among the materials identified by their manufacturers as "low shrinkage", only Filtek LS presented statistically lower values of shrinkage compared to composites based on conventional dimethacrylates, but lower degree of conversion as well. Overall materials with higher filler content presented higher initial values of flexural properties. However, their resistance to ethanol degradation seems to be influenced by different compositional factors and, therefore, cannot be directly related to water sorption results.
Asunto(s)
Resinas Compuestas/química , Etanol/química , Metacrilatos/química , Resinas de Silorano/química , Análisis de Varianza , Módulo de Elasticidad , Ensayo de Materiales , Solubilidad , Espectroscopía Infrarroja CortaRESUMEN
OBJECTIVES: To verify the hypothesis that crack analysis and a mechanical test would rank a series of composites in a similar order with respect to polymerization stress. Also, both tests would show similar relationships between stress and composite elastic modulus and/or shrinkage. METHODS: Soda-lime glass discs (2-mm thick) with a central perforation (3.5-mm diameter) received four Vickers indentations 500 µm from the cavity margin. The indent cracks were measured (500×) prior and 10 min after the cavity was restored with one of six materials (Kalore/KL, Gradia/GR, Ice/IC, Wave/WV, Majesty Flow/MF, and Majesty Posterior/MP). Stresses at the indent site were calculated based on glass fracture toughness and increase in crack length. Stress at the bonded interface was calculated using the equation for an internally pressurized cylinder. The mechanical test used a universal testing machine and glass rods (5-mm diameter) as substrate. An extensometer monitored specimen height (2mm). Nominal stress was calculated dividing the maximum shrinkage force by the specimen cross-sectional area. Composite elastic modulus was determined by nanoindentation and post-gel shrinkage was measured using strain gages. Data were subjected to one-way ANOVA/Tukey or Kruskal-Wallis/Mann-Whitney tests (alpha: 5%). RESULTS: Both tests grouped the composites in three statistical subsets, with small differences in overlapping between the intermediate subset (MF, WV) and the highest (MP, IC) or the lowest stress materials (KL, GR). Higher stresses were developed by composites with high modulus and/or high shrinkage. SIGNIFICANCE: Crack analysis demonstrated to be as effective as the mechanical test to rank composites regarding polymerization stress.
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Resinas Compuestas/química , Recubrimiento Dental Adhesivo/métodos , Análisis del Estrés Dental/métodos , Módulo de Elasticidad , Vidrio/química , Ensayo de Materiales/métodos , PolimerizacionRESUMEN
OBJECTIVES: The null hypothesis was that mechanical testing systems used to determine polymerization stress (σ(pol)) would rank a series of composites similarly. METHODS: Two series of composites were tested in the following systems: universal testing machine (UTM) using glass rods as bonding substrate, UTM/acrylic rods, "low compliance device", and single cantilever device ("Bioman"). One series had five experimental composites containing BisGMA:TEGDMA in equimolar concentrations and 60, 65, 70, 75 or 80 wt% of filler. The other series had five commercial composites: Filtek Z250 (3M ESPE), Filtek A110 (3M ESPE), Tetric Ceram (Ivoclar), Heliomolar (Ivoclar) and Point 4 (Kerr). Specimen geometry, dimensions and curing conditions were similar in all systems. σ(pol) was monitored for 10 min. Volumetric shrinkage (VS) was measured in a mercury dilatometer and elastic modulus (E) was determined by three-point bending. Shrinkage rate was used as a measure of reaction kinetics. ANOVA/Tukey test was performed for each variable, separately for each series. RESULTS: For the experimental composites, σ(pol) decreased with filler content in all systems, following the variation in VS. For commercial materials, σ(pol) did not vary in the UTM/acrylic system and showed very few similarities in rankings in the others tests system. Also, no clear relationships were observed between σ(pol) and VS or E. SIGNIFICANCE: The testing systems showed a good agreement for the experimental composites, but very few similarities for the commercial composites. Therefore, comparison of polymerization stress results from different devices must be done carefully.
Asunto(s)
Resinas Compuestas/química , Análisis del Estrés Dental/métodos , Módulo de Elasticidad , Ensayo de Materiales/instrumentación , Análisis de Varianza , Análisis del Estrés Dental/instrumentación , PolimerizacionRESUMEN
OBJECTIVES: Since photoinitiator systems for dental resins based on camphorquinone (CQ) present color disadvantages, trimethylbenzoyl-diphenyl-phosphine oxide (TPO) has been proposed as an alternative. However, there are remaining considerations about its curing efficiency. The aims of the present investigation were: to characterize the relationship between the photoinitiator absorption spectra and the light spectrum emitted from a QTH light (absorbed power density, PD(abs)); to evaluate the kinetics of polymerization, and the depth of cure for filled dimethacrylate resins formulated with different photoinitiator systems. METHODS: CQ+EDMAB (control); TPO and TPO+EDMAB were used in 50:50 Bis-GMA/TEGDMA resins. Photoinitiator absorption and QTH-light emission were evaluated using a spectrophotometer and kinetics of polymerization with differential scanning calorimetry (DSC) (n=3). Depth of cure was analyzed by the scraping method (n=5), as recommended by ISO4049. One-way ANOVA/Tukey's (p<0.05) was used to analyze the results. RESULTS: CQ presented higher PD(abs) than TPO (364 and 223 mW/cm(3), respectively). The DSC revealed that TPO and TPO+EDMAB produced a faster reaction than CQ+EDMAB. Composite formulated with CQ+EDMAB produced higher depth of cure (6.3±0.4 mm) than those with TPO (4.3±0.1) or TPO+EDMAB (4.2±0.3). SIGNIFICANCE: Although CQ presented higher PD(abs) than TPO, formulations containing TPO exhibited higher reactivity than that with CQ. On the other hand, materials formulated with TPO demonstrated lower depth of cure than that with CQ. Therefore, its use as an alternative photoinitiator requires further investigation, with higher concentrations.
Asunto(s)
Resinas Compuestas/química , Luces de Curación Dental , Curación por Luz de Adhesivos Dentales , Fotoiniciadores Dentales , Rastreo Diferencial de Calorimetría , Dureza , Cinética , Ensayo de Materiales , Fosfinas , Polimerizacion , Espectrofotometría , TerpenosRESUMEN
OBJECTIVE: To investigate the contributions of BisGMA:TEGDMA and filler content on polymerization stress, along with the influence of variables associated with stress development, namely, degree of conversion, reaction rate, shrinkage, elastic modulus and loss tangent for a series of experimental dental composites. METHODS: Twenty formulations with BisGMA:TEGDMA ratios of 3:7, 4:6, 5:5, 6:4 and 7:3 and barium glass filler levels of 40, 50, 60 or 70wt% were studied. Polymerization stress was determined in a tensilometer, inserting the composite between acrylic rods fixed to clamps of a universal test machine and dividing the maximum load recorded by the rods cross-sectional area. Conversion and reaction rate were determined by infra-red spectroscopy. Shrinkage was measured by mercury dilatometer. Modulus was obtained by three-point bending. Loss tangent was determined by dynamic nanoindentation. Regression analyses were performed to estimate the effect of organic and inorganic contents on each studied variable, while a stepwise forward regression identified significant variables for polymerization stress. RESULTS: All variables showed dependence on inorganic concentration and monomeric content. The resin matrix showed a stronger influence on polymerization stress, conversion and reaction rate, whereas filler fraction showed a stronger influence on shrinkage, modulus and loss tangent. Shrinkage and conversion were significantly related to polymerization stress. SIGNIFICANCE: Both the inorganic filler concentration and monomeric content affect polymerization stress, but the stronger influence of the resin matrix suggests that it may be possible to reduce stress by modifying resin composition without sacrificing filler content. The main challenge is to develop formulations with low shrinkage without sacrificing degree of conversion.
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Compuestos de Bario/química , Bisfenol A Glicidil Metacrilato/química , Materiales Dentales/química , Polietilenglicoles/química , Ácidos Polimetacrílicos/química , Dióxido de Silicio/química , Algoritmos , Química Farmacéutica , Análisis del Estrés Dental/instrumentación , Módulo de Elasticidad , Dureza , Humanos , Ensayo de Materiales , Docilidad , Polimerizacion , Espectroscopía Infrarroja Corta , Estrés Mecánico , Propiedades de Superficie , Factores de TiempoRESUMEN
PURPOSE: To determine the influence of rate of polymerization, degree of conversion and volumetric shrinkage on stress development by varying the amount of photoinitiators in a model composite. METHODS: Volumetric shrinkage (with a mercury dilatometer), degree of conversion, maximum rate of reaction (RPmax) (with differential scanning calorimetry) and polymerization stress (with a controlled compliance device) were evaluated. Bis-GMA/TEGDMA (equal mass ratios) were mixed with a tertiary amine (EDMAB) and camphorquinone, respectively, in three concentrations (wt%): high = 0.8/1.6; intermediate = 0.4/0.8 and low = 0.2/0.4. 80 wt% filler was added. Composites were photoactivated (400 mW/cm2 x 40 seconds; radiant exposure = l6 J/cm2). A fourth experimental group was included in which the low concentration formulation was exposed for 80 seconds (32 J/cm2). RESULTS: For the same radiant exposure, conversion, RPmax and stress increased with photoinitiator concentration (P < 0.001). When the low concentration group exposed to 32 J/cm2 was compared with the high and intermediate groups (exposed to 16 J/cm2), RPmax still increased with the photoinitiator concentration between all levels (P < 0.001) but conversion and stress did not vary (P > 0.05). Shrinkage did not vary regardless of the photoinitiator concentration or radiant exposure. For the photoinitiator concentrations used in this study. Polymerization stress was influenced by conversion but not by rate of reaction.
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Resinas Compuestas/química , Materiales Dentales/química , Ácido 4-Aminobenzoico/química , Bisfenol A Glicidil Metacrilato/química , Rastreo Diferencial de Calorimetría , Fenómenos Químicos , Química Farmacéutica , Adaptabilidad , Luces de Curación Dental , Humanos , Cinética , Ensayo de Materiales , Procesos Fotoquímicos , Polietilenglicoles/química , Polímeros/química , Ácidos Polimetacrílicos/química , Dosis de Radiación , Estrés Mecánico , Propiedades de Superficie , Terpenos/química , Factores de Tiempo , para-AminobenzoatosRESUMEN
OBJECTIVES: To evaluate (1) the influence of fluoride-containing adhesive on microtensile bond strength (microTBS) and (2) in vitro secondary caries inhibition at the resin-dentin interface after 24 h and 3 months water-storage and (3) the degree of conversion of different adhesives after 24h 1 month. METHODS: Flat surfaces of human teeth were ground and randomly assigned to six groups: (SBMP-24) Scotchbond Multi-Purpose control [SBMP], 24 h; (SE-24) SBMP etch and primer+Clearfil SE Bond adhesive [SE], 24h; (PB-24) SBMP etch and primer+Clearfil Protect Bond adhesive [PB], 24h; (SBMP-3) SBMP, 3 months; (SE-3) SBMP+SE, 3 months; and (PB-3) SBMP+PB, 3 months. To evaluate the effect of the adhesive resin alone, all teeth were etched with 35% phosphoric acid and primed with SBMP primer prior to applying the adhesive resin. Bonded assemblies were prepared for microTBS and stored in distilled water at 37 degrees C for 24h and 3 months. Sections of restored teeth of each group were exposed to an acid challenge. The specimens were sectioned, polished, and then observed with polarized light microscopy (PLM). Also, the degree of conversion (DC) of the adhesives was measured using Fourier Transform-Infrared spectroscopy (FTIR) at 24 h and 1 month, after polymerization. RESULTS: microTBS values obtained in MPa (24h/3m) were: (MP) 61.5+/-10.5/52.9+/-8.9, (SE) 55.5+/-11.8/55.6+/-13, and (PB) 50.3+/-9.9/61.0+/-13.6. For interface analysis by PLM, an inhibition zone (IZ) adjacent to the hybrid layer was created only when the fluoride-containing adhesive (PB) was used. The DC in percentage (24 h, 1 month) were: (MP) 60.5+/-2.8/61.3+/-0.6, (SE) 69.6+/-1.3/70.7+/-0.05, and (PB) 53.1+/-0.4/58.3+/-1.6. SIGNIFICANCE: The fluoride-containing adhesive demonstrated significant increase of bond strength values after water-storage. This material was also able to create an acid inhibition zone in dentin. There was a significant increase of degree of conversion after 1 month only for PB.
Asunto(s)
Cariostáticos/química , Recubrimientos Dentinarios/química , Dentina/ultraestructura , Fluoruros/química , Grabado Ácido Dental , Ácidos/química , Cariogénicos/química , Resinas Compuestas/química , Caries Dental/patología , Humanos , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Microscopía de Polarización , Organofosfonatos/química , Polímeros/química , Cementos de Resina/química , Silanos/química , Espectroscopía Infrarroja por Transformada de Fourier , Estrés Mecánico , Propiedades de Superficie , Temperatura , Resistencia a la Tracción , Factores de Tiempo , Agua/químicaRESUMEN
This study evaluated the influence of adhesive layer thickness (ADL) on the resin-dentin bond strength of two adhesive systems (AS) after thermal and mechanical loading (TML). A flat superficial dentin surface was exposed with 600-grit SiC paper on 40 molars. After primer application, the adhesive layer of Scotchbond Multipurpose (SBMP) or Clearfil SE Bond (CSEB) was applied in one or two layers to a delimited area (52 mm2) and resin blocks (Filtek Z250) were built incrementally. Half of the sample was stored in distilled water (37 degrees C, 24 hours) and submitted to thermal (1,000; 5 degrees -55 degrees C) and mechanical cycles (500,000; 10kgf) [TML]. The other half was stored in distilled water (72 hours). The teeth were then sectioned to obtain sticks (0.8 mm2) to be tested under tensile mode (1.0 mm/minute). The fracture mode was analyzed at 400x. The BS from all sticks from the same tooth was averaged for statistical purposes. The data was analyzed by three-way ANOVA. The chi2 test was used (p < 0.05) to compare the frequency of pre-testing failure specimens. Higher BS values were observed for SBMP regardless of the ADL. The TML reduced the BS values irrespective of the adhesive employed and the ADL. A higher frequency of pre-testing failure specimens was observed for the cycled groups. A thicker adhesive layer, acting as an intermediate flexible layer, did not minimize the damage caused by thermal/mechanical load cycling for a three-step etch-and-rinse and two-step self-etch system.
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Recubrimiento Dental Adhesivo , Recubrimientos Dentinarios/química , Dentina/ultraestructura , Grabado Ácido Dental/métodos , Compuestos Inorgánicos de Carbono/química , Resinas Compuestas/química , Materiales Dentales/química , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Docilidad , Cementos de Resina/química , Compuestos de Silicona/química , Capa de Barro Dentinario , Estrés Mecánico , Propiedades de Superficie , Temperatura , Resistencia a la Tracción , Agua/químicaRESUMEN
OBJECTIVES: Stress development during the polymerization process continues to be a major factor that limits predictability and longevity of resin composite restorations. This study evaluated the effect of the photoinitiator type on the maximum rate of polymerization (R(p)(max)), stress development (final stress and maximum rate, R(stress)(max)), degree of conversion (DC) and cross-link density (CLD) of materials containing camphorquinone (CQ), phenylpropanedione (PPD) or CQ/PPD. MATERIALS AND METHODS: R(p)(max) was evaluated via differential scanning calorimetry (DSC). Contraction force measurement was assessed with a single cantilever device for 5min. The samples were subsequently tested by infrared spectroscopy (FTIR) to evaluate the DC. After, samples were soaked in ethanol to evaluate the swelling coefficient (alpha) as a way to estimate the CLD. The results were analyzed by one-way ANOVA and Tukey's test (p=0.05). RESULTS: CQ showed the highest R(p)(max) and R(stress)(max). PPD produced the lowest DC and the highest alpha. The mixture CQ/PPD produced statistically lower R(p)(max) and R(stress)(max) than CQ alone, but similar DC and CLD. CONCLUSION: CQ/PPD reduced the R(p)(max) and R(stress)(max) without a reduction in DC and CLD. Therefore, the use of alternative photoinitiator systems could be a promising way to reduce the stress developed during the composite's polymerization without affecting the final properties.
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Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Curación por Luz de Adhesivos Dentales/métodos , Bisfenol A Glicidil Metacrilato , Chalconas , Luces de Curación Dental , Análisis del Estrés Dental , Módulo de Elasticidad , Transición de Fase , Procesos Fotoquímicos , Polietilenglicoles , Ácidos Polimetacrílicos , TerpenosRESUMEN
OBJECTIVES: To evaluate the effect of amine ratio (ethyl 4-dimethylaminobenzoate, EDMAB) on the maximum rate of polymerization (R(p)(max)), degree of conversion (DC), Knoop hardness (KH), water sorption (Wsp), water solubility (Wsl) and color changes (DeltaE) over time of resin composites formulated with the photoinitiators camphorquinone (CQ), phenylpropanedione (PPD) and CQ-PPD in combination. MATERIALS AND METHODS: Experimental resin composites were made with photoinitiator:amine ratios of 2:1, 1:1, 1:1.5 and 1:2 by weight. R(p)(max) was evaluated with differential scanning calorimetry (DSC), DC with DSC and Fourier transformed infrared (FTIR) spectroscopy, KH with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and color with a chromameter. The results were analyzed with two-way ANOVA/Tukey's multiple comparison test (p<0.05). RESULTS: The higher the amine ratio in the composite, the higher was DC, R(p)(max), and KH, and the lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ-PPD. Many factors seem to affect the color changes and the b-axis data revealed that the higher the amine ratio, the higher was the +b value (yellowing) for CQ and CQ-PPD formulations. CONCLUSIONS: Higher amine ratios led to improved polymer properties, but also produced more yellowing in resin composites with CQ and CQ-PPD. The use of PPD alone was not advantageous for producing good final properties when compared to CQ and CQ-PPD.
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Chalconas/química , Resinas Compuestas/química , Materiales Dentales/química , Terpenos/química , Ácido 4-Aminobenzoico/química , Absorción , Adsorción , Bisfenol A Glicidil Metacrilato/química , Rastreo Diferencial de Calorimetría , Fenómenos Químicos , Color , Dureza , Humanos , Ensayo de Materiales , Polietilenglicoles/química , Polímeros/química , Ácidos Polimetacrílicos/química , Solubilidad , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Agua/química , para-AminobenzoatosRESUMEN
OBJECTIVES: The purpose of this study was to investigate the effect of different surface treatments on the bond strength (sigma) of repaired, aged resin composites (ARC). METHODS: Forty blocks of Filtek Z250 (Z2) and Filtek Supreme (SU) were made, stored in deionized water for 9 days, and randomly assigned to different surface treatment groups: hydrofluoric acid etching (HA), abrasion using a coarse diamond bur (AB), sandblasting with alumina particles (AO), and silica coating (SC). The average roughness (Ra) of the treated surfaces was measured with a profilometer. An adhesive system (SB-Adper Single Bond Plus), a silane (SI) or a combination of both (SI+SB) were applied after each surface treatment. The blocks were restored with the same composite (RC) and cut to produce bars that were turned into dumbbell-shaped specimens (0.5mm(2)) using a precision grinding machine. The specimens (n=30) were tested in tension to fracture and the microtensile bond strength (sigma) values were calculated (MPa). Data were analyzed using three-way ANOVA/Tukey test (alpha=0.05) and Weibull statistics. RESULTS: AO and SC produced similar Ra values, which were greater than the value produced by HA. The sigma values were statistically influenced by the type of RC (p<0.0001), by the surface treatment (p<0.0001) and by the surface coating (p<0.0001). Treating the surface of Z2 with SC+SB produced the greatest m value. SIGNIFICANCE: AO and SC produced the greatest sigma values, irrespective of the primer (SI, SB or SI+SB) used. Yet, the RC microstructure influenced the mean sigma values, which were greater for Z2 than for SU. The HA should not be used for repairing ARC.
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Resinas Compuestas , Recubrimiento Dental Adhesivo , Reparación de Prótesis Dental , Cementos de Resina , Grabado Ácido Dental , Óxido de Aluminio , Bisfenol A Glicidil Metacrilato , Materiales Biocompatibles Revestidos , Restauración Dental Permanente , Análisis del Estrés Dental , Ensayo de Materiales , Nanocompuestos , Distribución Aleatoria , Silanos , Dióxido de Silicio , Propiedades de Superficie , Análisis de Supervivencia , Resistencia a la TracciónRESUMEN
OBJECTIVES: To characterize the microstructure and composition of two different composites, and to determine their influence on the physical properties and fracture behavior. METHODS: The microstructure and composition of a microhybrid (Filtek Z250-Z2) and a nanofill (Filtek Supreme-SU) composite were analyzed using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). Filler wt% was determined by thermogravimetric analysis. Hardness (H) and degree of conversion (DC) were evaluated at top and bottom surfaces of 2-mm thick specimens, and the dynamic elastic modulus (E) was determined with ultrasonic waves. Bar specimens (n=30) were subjected to flexure loading and flexural strength (sigmaf) was calculated (MPa). Fractographic analysis (FA) was performed to determine the fracture origin (c) for calculation of fracture toughness (KIc), and these results were compared to those from the single edge notch beam (SENB) method. Results were statistically analyzed using two-way ANOVA, Student's t-test and Weibull analysis (alpha=0.05). RESULTS: Z2 had higher filler wt%, H, E and DC at 2-mm depth as compared with SU. The fracture behavior (sigmaf and KIc) and the structural reliability (m) of the composites were similar. Results of KIc tested by SENB or calculated from fracture surfaces from flexure testing were similar. SIGNIFICANCE: The microstructural organization of the composites determines their physical properties, in spite of the similar filler content. In contrast, the microstructure did not influence the fracture behavior and the structural reliability of these highly filled composites. FA was shown to be a reliable method for determining the KIc of composites.
Asunto(s)
Resinas Compuestas/química , Materiales Dentales/química , Nanocompuestos/química , Algoritmos , Elasticidad , Microanálisis por Sonda Electrónica , Dureza , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Docilidad , Polímeros/química , Dióxido de Silicio/química , Espectroscopía Infrarroja por Transformada de Fourier , Estrés Mecánico , Propiedades de Superficie , Termogravimetría , Ultrasonido , Circonio/químicaRESUMEN
OBJECTIVES: To evaluate the degree of conversion (DC), maximum rate of polymerization (Rpmax), Knoop hardness (KHN) and yellowing (b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less Rpmax and yellowing than CQ alone without affecting DC and KHN, and (ii) Rpmax, DC, and KHN would be directly related to the absorbed power density (PDabs). METHODS: CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, Rp with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student-Newman-Keul's test (p<0.05). Correlation tests were carried out between PDabs and each of DC, Rpmax and KHN. RESULTS: The PDabs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while Rpmax and KHN required higher concentrations. DC was similar for all photoinitiators, but Rpmax was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PDabs showed significant correlations with DC, Rpmax and KHN. CONCLUSION: PPD or CQ/PPD reduced Rpmax in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, Rpmax and KHN were dependent on PDabs.
Asunto(s)
Resinas Compuestas/química , Materiales Dentales/química , Ácido 4-Aminobenzoico/química , Ácido 4-Aminobenzoico/efectos de la radiación , Absorción , Bisfenol A Glicidil Metacrilato/química , Bisfenol A Glicidil Metacrilato/efectos de la radiación , Rastreo Diferencial de Calorimetría , Chalconas/química , Chalconas/efectos de la radiación , Color , Resinas Compuestas/efectos de la radiación , Materiales Dentales/efectos de la radiación , Dureza , Humanos , Ensayo de Materiales , Polietilenglicoles/química , Polietilenglicoles/efectos de la radiación , Polímeros/química , Polímeros/efectos de la radiación , Ácidos Polimetacrílicos/química , Ácidos Polimetacrílicos/efectos de la radiación , Dosis de Radiación , Espectrofotometría Ultravioleta , Espectroscopía Infrarroja por Transformada de Fourier , Terpenos/química , Terpenos/efectos de la radiación , para-AminobenzoatosRESUMEN
OBJECTIVES: The aim of the present study was to evaluate the flexural strength and the Weibull modulus of a microhybrid and a nanofill composite by means of 3- and 4-point bending tests. METHODS: Thirty specimens of Filtek Z250 (3M/ESPE) and Filtek Supreme (3M/ESPE) were prepared for each test according to the ISO 4049/2000 specification. After 24h in distilled water at 37 degrees C the specimens were submitted to 3- and 4-point bending tests using a universal testing machine DL2000 (EMIC) with a crosshead speed of 1 mm/min. Flexural strength data were calculated and submitted to Student's t-test (alpha=0.05) and Weibull statistics. The fractured surfaces were analyzed based on fractographic principles. RESULTS: The two composites had equivalent strength in both test methods. However, the test designs significantly affected the flexural strength of the microhybrid and the nanofill composites. Weibull modulus (m) of Supreme was similar with both tests, while for Z250, a higher m was observed with the 3-point bending test. Critical flaws were most often associated with the specimen's surface (up to 90%) and were characterized as surface scratches/grooves, non-uniform distribution of phases, inclusions and voids. SIGNIFICANCE: Flexural strength as measured by the 3-point bending test is higher than by the 4-point bending test, due to the smaller flaw containing area involved in the former. Despite the large difference in average filler size between the composites, the volume fraction of the filler in both materials is similar, which was probably the reason for similar mean flexural strength values and fracture behavior.
Asunto(s)
Resinas Compuestas , Resinas Compuestas/química , Análisis del Estrés Dental/métodos , Ensayo de Materiales , Nanocompuestos , Tamaño de la Partícula , Docilidad , Análisis de SupervivenciaRESUMEN
OBJECTIVES: The objective of this study was to verify the influence of curing methods on contraction stress, stress rate and degree of conversion (DC) of a restorative composite at two C-factor levels. METHODS: For the stress test, composite was applied between two for 15 min from diameter glass rods mounted in a servohydraulic machine, and stress was monitored for 10 min from the beginning of light curing. Stress rates were calculated as the change in stress versus time at each second. DC was measured by micro-FTIR. Four curing methods were tested at two C-factor levels (1.5 and 3.0): continuous light (CL), soft-start (SS) and two pulse delay methods using different initial irradiances--150 mW/cm(2) (PD150) and 80 mW/cm(2) (PD80). Results were analyzed by ANOVA and Tukey's test (alpha=0.05). RESULTS: For the stress test, at CF 1.5, PD80 presented the lowest mean value, statistically different from the others. PD150 also showed a mean value statistically inferior to CL. At CF 3.0, no statistical difference was observed among CL, SS and PD150. PD80 presented statistically lower stress values compared to CL and SS. Stress values at CF 3.0 were statistically higher than those at CF 1.5 for all curing methods. CL presented the highest maximum stress rate, followed by SS, PD150 and PD80, for both C-factors. In the DC test, no difference was observed among the methods and between the C-factor levels. SIGNIFICANCE: Modulated curing methods were shown to be effective in reducing contraction stress rate, without compromising the DC of the restorative composite. C-factor was shown to influence negatively the stress rate and the amount of stress generated.
Asunto(s)
Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Análisis del Estrés Dental , Análisis de Varianza , Adaptación Marginal Dental , Luz , Ensayo de Materiales , Transición de Fase , Espectroscopía Infrarroja por Transformada de Fourier , Estadísticas no ParamétricasRESUMEN
PURPOSE: To evaluate the wear differences between primary and permanent enamel caused by the association of abrasion and erosion. METHODS: Fragments of 40 human teeth (20 primary and 20 permanent) were cast in acrylic rings, polished to expose a flat enamel area, and evaluated with a 3D profiler. Antagonists were made from primary and permanent molars. The specimens were distributed into four groups (n = 10) according to type of substrate and slurry (neutral and acidic), and cycled 100,000 times in the OHSU oral wear simulator. Specimens were cleaned and re-profiled. Volume loss and maximum depth were determined on the polished specimens. Data were submitted to ANOVA and Tukey's test. The area of the wear facet on the antagonist was measured. RESULTS: Primary enamel showed more wear than permanent enamel, regardless of the slurry type. The acidic environment increased the wear rate compared to the neutral slurry. The association of abrasion and erosion increased the wear rate for the primary teeth only. There was no significant difference among groups for cusp wear and no correlation between cusp wear and the enamel wear.
Asunto(s)
Esmalte Dental/patología , Abrasión de los Dientes/patología , Erosión de los Dientes/patología , Diente Primario/patología , Adolescente , Adulto , Niño , Ácido Cítrico/farmacología , Susceptibilidad a Enfermedades , Femenino , Humanos , Concentración de Iones de Hidrógeno , Imagenología Tridimensional , Masculino , Microscopía Electrónica de Rastreo , Polimetil Metacrilato/química , Abrasión de los Dientes/etiología , Erosión de los Dientes/etiología , Agua/farmacologíaRESUMEN
PURPOSE: To evaluate the effect of dental materials on primary enamel wear. METHODS: Four composites (Filtek Z250, Heliomolar, Point 4, SureFil), two compomers (Dyract AP, F2000) and a resin-modified glass-ionomer (Vitremer) were placed into box-shaped preparations in buccal surfaces of primary molars and stored for 24 hours in water at 37 degrees C. The specimens (n = 6) were subjected to abrasive three-body wear against a primary enamel cusp. Material wear, enamel wear (adjacent to the material), and wear on enamel cusps were estimated by profilometry and video-analysis software. Results were compared with ANOVA and Tukey's tests (P < 0.05). RESULTS: Vitremer showed the highest wear (P < 0.05), followed by Dyract AP and F2000, which were not statistically different (P > 0.05). There was no significant difference between Filtek Z250 and Dyract AP (P > 0.05). Filtek Z250, Heliomolar, Point 4 and SureFil, showed the lowest wear values and there was no difference among them (P > 0.05). The highest wear values on the enamel adjacent to the material were found with Dyract AP (P < 0.05) and the lowest next to Point 4 and SureFil (P < 0.05). There was no difference in the wear of the enamel next to Vitremer, F2000, Heliomolar and Filtek Z250 (P > 0.05). Vitremer and F2000 caused the highest wear on enamel cusps (P < 0.05), and there was no statistically significant difference (P > 0.05) between them; SureFil caused the lowest wear (P < 0.05) on the opposing enamel. There was a correlation (r = 0.85) between wear of materials and wear on the enamel cusps, but not (r = 0.53) for the wear on enamel besides the restoration and wear on enamel cusps. SEM micrographs showed different surface characteristics of the materials after the wear test.