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1.
Niger J Clin Pract ; 23(8): 1148-1154, 2020 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-32788494

RESUMEN

Aims: The effect of mechanical loading on the microtensile bond strength (µTBS) of universal adhesives to dentin was evaluated in this study. Methods and Materials: Human molar teeth had the occlusal dentin surfaces exposed and were allocated into ten groups (five experimental groups and five control groups) that used the following universal adhesive systems in self-etch mode: All-Bond Universal (ABU), Single Bond Universal (SBU), Gluma Bond Universal (GBU), Tetric N-Bond Universal (TBU), and Clearfil Universal Bond (CUB). Following the bonding procedures and build-ups, the specimens were either stored in water at 37°C for 24 h or were mechanically loaded (50 N for 60,000 cycles) prior to the µTBS test. Data were analyzed using the one-way analysis of variance (ANOVA) and Tukey's posthoc test (P = 0.05). Results: Both the adhesive type and mechanical loading had significant effects on the µTBS (P < 0.05). The µTBS values of SBU and ABU were significantly higher than the values of the other adhesives (P < 0.05). However, the µTBS values of ABU decreased significantly after mechanical loading (P < 0.05). Conclusions: With the exception of ABU, mechanical loading had no deleterious effects on the µTBS of the universal adhesive systems examined in this study.


Asunto(s)
Adhesivos/química , Recubrimiento Dental Adhesivo/métodos , Recubrimientos Dentinarios/química , Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Glutaral , Humanos , Ensayo de Materiales/métodos , Diente Molar , Ácidos Polimetacrílicos , Cementos de Resina/química , Resistencia a la Tracción
2.
Braz Oral Res ; 34: e099, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32785474

RESUMEN

The composition of infiltrants can influence their physical properties, viscosity and depth of penetration (DP). Strategies are used to increase the DP, such as the addition of diluents or the use of heat. This study aimed to evaluate the effect of preheating and composition on physical properties and DP of infiltrants in demineralized enamel. The groups were assigned, and the following experimental formulations were made: 25%BisEMA +75%TEGDMA; 25%BisEMA +65%TEGDMA +10%ethanol; 25%BisEMA +65%TEGDMA +10%HEMA; 100%TEGDMA; 90%TEGDMA +10%ethanol; 90%TEGDMA +10%HEMA. The samples were photoactivated at two temperatures (25°C and 55°C). Degree of conversion (DC) was performed using an infrared spectrophotometer. Elastic modulus (E), flexural strength (FS) and contact angle (CA) tests were also performed. The DP of an infiltrant in demineralized enamel was determined by confocal laser scanning microscopy (CLSM) using an indirect labeling technique. The data were analyzed by two-way ANOVA and Tukey's test. DC increased after preheating in all the groups; however, 90%TEGDMA+10%ethanol showed the lowest DC for both temperatures, and the lowest E. Preheating did not influence E or FS. The CA increased at 55°C for most groups, but decreased for groups containing HEMA. Temperature did not seem to influence DP, and Icon showed the lowest DP values. The 100%TEGDMA composition showed more homogeneous penetration, whereas Icon showed heterogeneous and superficial penetration. The preheating technique does not improve all properties in all the material compositions. The composition of a material can influence and improve its properties.


Asunto(s)
Esmalte Dental , Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Módulo de Elasticidad , Ensayo de Materiales , Metacrilatos , Polietilenglicoles , Ácidos Polimetacrílicos , Viscosidad
3.
Dent Mater ; 36(7): 884-892, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32402514

RESUMEN

OBJECTIVE: Water sorption, high volumetric shrinkage, polymerization stress, and potential estrogenic effects triggered by leached compounds are some of the major concerns related to BisGMA-TEGDMA co-monomer systems used in dental composites. These deficiencies call for the development of alternative organic matrices in order to maximize the clinical lifespan of resin composite dental restorations. This study proposes BisGMA-free systems based on the combination of UDMA and a newly synthesized diurethane dimethacrylate, and evaluates key mechanical and physical properties of the resulting materials. METHODS: 2EMATE-BDI (2-hydroxy-1-ethyl methacrylate) was synthesized by the reaction between 2-hydroxy-1-ethyl methacrylate with a difunctional isocyanate (1.3-bis (1- isocyanato-1-methylethylbenzene) - BDI). The compound was copolymerized with UDMA (urethane dimethacrylate) at 40 and 60wt%. UDMA copolymerizations with 40 and 60wt% TEGDMA (triethylene glycol dimethacrylate) were tested as controls, as well as a formulation based in BisGMA (bisphenol A-glycidyl methacrylate)-TEGDMA 60:40% (BT). The organic matrices were made polymerizable by the addition of DMPA (2.2-dimethoxyphenoxy acetophenone) and DPI-PF6 (diphenyliodonium hexafluorophosphate) at 0.2 and 0.4wt%, respectively. Formulations were tested as composite with the addition of 70wt% inorganic content consisting of barium borosilicate glass (0.7µm) and fumed silica mixed in 95 and 5wt%, respectively. All photocuring procedures were carried out by a mercury arc lamp filtered to 320-500nm at 800mW/cm2. The experimental resin composites were tested for kinetics of polymerization and polymerization stress in real time. Flexural strength, elastic modulus, water sorption, and solubility were assessed according to ISO 4049. Biofilm formation was analyzed after 24h by luciferase assay. Data were statistically analyzed by one-way ANOVA and Tukey's test (α≤0.05). RESULTS: In general, the addition of 2EMATE-BDI into the formulations decreased the maximum rate of polymerization (RPMAX), the degree of conversion at RPMAX (DC at RPMAX), and the final degree of conversion (final DC). However, these reductions did not compromise mechanical properties, which were comparable to the BT controls, especially after 7-day water incubation. The incorporation of 60wt% 2EMATE-BDI reduced water sorption of the composite. 2EMATE-BDI containing formulations showed reduction in polymerization stress of 30% and 50% in comparison to BT control and TEGDMA copolymerizations, respectively. Biofilm formation was similar among the tested groups. SIGNIFICANCE: The use of the newly synthesized diurethane dimethacrylate as co-monomer in dental resin composite formulations seems to be a promising option to develop polymers with low-shrinkage and potentially decreased water degradation.


Asunto(s)
Resinas Compuestas , Metacrilatos , Bisfenol A Glicidil Metacrilato , Módulo de Elasticidad , Ensayo de Materiales , Polietilenglicoles , Polimerizacion , Ácidos Polimetacrílicos
4.
Oper Dent ; 45(5): 547-555, 2020 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-32352351

RESUMEN

CLINICAL RELEVANCE: The photo-initiator system based on an advanced polymerization system may be an alternative that can be used to overcome the disadvantages of radicular dentin, especially for the apical third. SUMMARY: Objectives: The purpose of this study was to evaluate the effects of universal adhesives with different photo-initiator systems applied in etch-and-rinse (ER) and self-etch (SE) modes on dentin interaction (push-out bond strength [PBS], nanoleakage [NL], and degree of conversion [DC] within the hybrid layer) in the different root thirds after fiber post cementation.Methods and Materials: Roots of endodontically prepared human premolars were randomly divided into six groups according to one of three adhesive systems (Scotchbond Universal [SBU], Ambar Universal [AMB], and Ambar Universal APS [AMB-APS]) and two adhesive strategies (ER and SE) for each system. Posts were cemented, and PBS was tested at 0.5 mm/min. The NL was evaluated by scanning electron microscopy. DC was measured using micro-Raman spectroscopy. The data were analyzed by three-way analysis of variance and Tukey tests (α=0.05).Results: AMB-APS showed similar performance in all root thirds (p>0.05) and higher values of DC, especially in the apical third (p<0.0001). AMB and SBU showed the lowest values in the apical third (p<0.0001).Conclusions: The APS photo-initiator system contained in universal adhesives is a feasible alternative for improving radicular bonding procedure.


Asunto(s)
Recubrimiento Dental Adhesivo , Recubrimientos Dentinarios , Adhesivos , Bisfenol A Glicidil Metacrilato , Cementos Dentales , Dentina , Humanos , Ensayo de Materiales , Cementos de Resina , Resistencia a la Tracción
5.
Am J Dent ; 33(2): 69-73, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32259410

RESUMEN

PURPOSE: To evaluate marginal seal, adaptation, surface texture, and bubble presence of pit and fissure sealants when using a novel instrument (C-Shape It) or the manufacturers' supplied applicators for sealant placement into occlusal fissures. METHODS: Extracted molars with occlusal fissures were cleaned with pumice slurry and divided into six groups (n= 10/gp); three treatment and three control. Sealant materials placed included Ultraseal, Delton, and Helioseal. Excess water was removed per manufacturers' instructions. Sealants were applied with each applicator and with the C-Shape It to each group from cusp to cusp without covering marginal ridges, and the polymerization guidelines for photocuring were followed for all the groups. Samples were thermocycled at 500x between 5° and 55°C. Teeth were sectioned in a buccolingual direction with a minimum of four sections per tooth and examined under a light microscope at 50x and scored. RESULTS: Marginal seal, adaptation, penetration ability, surface texture, bubble formation and location of the sealants were analyzed using two-way ANOVA on ranks with a 95% confidence interval. The C-Shape It instrument showed consistently smoother surface texture (P< 0.001), which was statistically significant versus all manufacturers' applicators for all materials. Bubble presence was statistically significantly less with the instrument C-Shape It versus the manufacturers' applicators for all materials (P< 0.001). Results also revealed significant differences in marginal sealant adaptation. CLINICAL SIGNIFICANCE: C-Shape It demonstrated consistent ability to reduce bubbles and improve surface texture and adaptation in occlusal fissures for all pit and fissure products tested.


Asunto(s)
Filtración Dental , Selladores de Fosas y Fisuras , Bisfenol A Glicidil Metacrilato , Diente Molar
6.
J Dent ; 94: 103306, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-32112910

RESUMEN

OBJECTIVES: This study investigated the effects of the surface conditioning of nano-zirconia fillers with 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and dipentaerythritol penta-acrylate phosphate (PENTA) on the degree of conversion and mechanical properties of Bis-GMA- and UDMA-based resin composites containing the fillers. METHODS: MDP or PENTA conditioned nano-zirconia fillers were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The conditioned nano-zirconia fillers were then used to prepare Bis-GMA- and UDMA-based resin composites. The bending strength and elastic modulus of the prepared composites were evaluated, and Weibull analysis was adopted to evaluate the reliability of the bending tests. Degree of conversion (DC) was measured by FTIR. RESULTS: FTIR and XPS analysis confirmed formation of ZrOP bonds in the MDP-conditioned and PENTA-conditioned zirconia fillers. MDP-conditioning and PENTA-conditioning increased bending strength of Bis-GMA-based composites (100.70 ±â€¯7.15 MPa, 98.65 ±â€¯4.76 Mpa) and UDMA-based composites (99.02 ±â€¯4.45 MPa, 99.92 ±â€¯5.78 MPa) compared to the groups with untreated nano-zirconia fillers (Bis-GMA-based, 84.98 ±â€¯5.13 MPa; UDMA-based, 88.24 ±â€¯4.61 MPa). The same trend was observed for the Weibull modulus (m) and elastic modulus. The MDP/PENTA conditioning did not affect the DC of the composites. CONCLUSION: MDP or PENTA conditioning of nano-zirconia fillers improved the mechanical properties of the composite compared to the composites containing untreated nano-zirconia fillers; however, it did not affect DC. CLINICAL SIGNIFICANCE: Mixing MDP- or PENTA-conditioned nano-zirconia fillers directly with gamma-MPS-conditioned silica to the resin composite has the potential to improve the composite's mechanical properties.


Asunto(s)
Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Metacrilatos , Ensayo de Materiales , Fosfatos , Reproducibilidad de los Resultados , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Circonio
7.
Niger J Clin Pract ; 23(2): 165-171, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-32031090

RESUMEN

Aims: The aim of this study is to evaluate the effect of the diode laser used for dentin sensitivity on the clinical success of non-carious cervical lesion (NCCL) restorations restored with different adhesive systems. Methods: 20 NCCLs were restorated with Universal Single Bond (Self Etch) (3M, USA) and Grandio (Voco, Germany), 20 NCCLs were restorated with Universal Single Bond (Total Etch) and Grandio. After diode laser application, 20 NCCLs were restorated with Universal Single Bond and Grandio, 20 NCCLs were restorated with Universal Single Bond (Total Etch) and Grandio. The restorations were clinical evaluated by two examiners at baseline, for 6 and 18 months using modified United States Public Health Service (USPHS) Criteria. Chi-square test was used for statistical analyse. Results: The lowest rates of retention was found in the Group 1. There was no statistically significant difference among the groups in marginal discoloration, marginal integrity, sensitivity (P > 0.05). Conclusion: Diode laser application prior to the restoration of teeth with NCCL don't reduce the retention rate of restorations, may reduce hypersensitivity and may affect the success of restoration. However, further laboratory and clinical studies are required.


Asunto(s)
Adhesivos/farmacología , Resinas Compuestas , Grabado Dental , Restauración Dental Permanente/métodos , Láseres de Semiconductores/uso terapéutico , Cuello del Diente , Adulto , Bisfenol A Glicidil Metacrilato , Adaptación Marginal Dental , Sensibilidad de la Dentina , Recubrimientos Dentinarios , Femenino , Estudios de Seguimiento , Humanos , Láseres de Semiconductores/efectos adversos , Masculino , Persona de Mediana Edad
8.
Eur J Oral Sci ; 128(1): 89-99, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-32032451

RESUMEN

In this study, polyurethane dimethacrylate (PUDMA) was synthetized from different components and incorporated into a direct resin composite restoration system with the aim to buffer tooth-resin interfacial stresses and maintain the marginal adaptation. The tensile strength, elongation at fracture (ε), and thermal stability of the PUDMA layer were characterized, showing a tensile strength of 22 MPa, an ε of 112%, and a thermal decomposition temperature of about 282°C. In addition, the degree of conversion, water sorption/solubility, hydrophobicity, microtensile bond strength (µTBS), marginal leakage, and cytotoxicity in vitro were evaluated for the PUDMA layer. The data were analyzed using one-way ANOVA, except for leakage depths (which were analyzed using the Wilcoxon paired-rank test). The level of significance was set at 0.05. Compared with dental adhesives, PUDMA displayed a higher degree of conversion, lower water sorption/solubility, and improved hydrophobicity and biocompatibility in vitro. After thermocycling, the µTBS of the restoration system containing PUDMA had increased compared with the µTBS at 24 h. Restorations containing PUDMA showed lower leakage depths than those which did not contain PUDMA. In conclusion, because of its hydrophobic and elastic nature, the PUDMA layer, when used as an intermediate between tooth and resin restoratives, may buffer interfacial stresses, improve the stability and durability of the bonding interface, and reduce microleakage.


Asunto(s)
Metacrilatos , Poliuretanos , Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Recubrimiento Dental Adhesivo , Preparación de la Cavidad Dental , Filtración Dental , Recubrimientos Dentinarios , Humanos , Ensayo de Materiales , Cementos de Resina , Resistencia a la Tracción
9.
Dent Mater ; 36(3): 468-477, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-32005546

RESUMEN

OBJECTIVE: The aim of this study was to investigate the influence of the photoinitiator system on the polymerization kinetics of methacrylamide-based monomers as alternatives to methacrylates in adhesives dental-based materials. METHODS: In total, 16 groups were tested. Monofunctional monomers (2-hydroxyethyl methacrylate) - HEMA; (2-hydroxy-1-ethyl methacrylate) -2EMATE, (2-hydroxyethyl methacrylamide) - HEMAM; and (N-(1-hydroxybutan-2-yl) methacrylamide) -2EM; were combined with bifunctional monomers containing the same polymerizing moieties as the monofunctional counterparts (HEMA-BDI; 2EMATE-BDI; HEMAM-BDI; and 2EM-BDI) at 50/50 M ratios. BHT was used as inhibitor (0.1 wt%) and the photoinitiators used were: CQ + EDMAB (0.2/0.8), BAPO (0.2), IVOCERIN (0.2), and DMPA (0.2), in wt%. The polymerization kinetics were monitored using Near-IR spectroscopy (∼6165 cm-1) in real-time while the specimens were photoactivated with a mercury arc lamp (Acticure 2; 320-500 nm, 300 mW/cm2) for 5 min, and maximum rate of polymerization (Rpmax, in %.s-̄1), degree of conversion at Rpmax (DC@Rpmax, in %), and the final degree of conversion (Final DC, in %) were calculated (n = 3). Initial viscosity was measured with an oscillating rheometer (n = 3). Data were analyzed using Two-way ANOVA for the polymerization kinetics and one-way ANOVA for the viscosity. Multiple comparisons were made using the Tukey's test (∝ = 0.05). RESULTS: There was statistically significant interaction between monomer and photoinitiator (p < 0.001). For the methacrylates groups, the highest Rpmax was observed for HEMA + DMPA and 2EMATE + BAPO. For methacrylamides groups, the highest Rpmax were observed for HEMAM and 2EM, both with DMPA. Final DC was higher for the methacrylate groups, in comparison with methacrylamide groups, independent of the photoinitiators. However, for the methacrylamide groups, the association with BAPO led to the lowest values of DC. In terms of DC@Rpmax, methacrylate-based systems showed significantly higher values than methacrylamide formulations. DMPA and Ivocerin led to higher values than CQ/EDMAB and BAPO in methacrylamide-based compounds. BAPO systems showed de lowest values for both HEMA and HEMAM formulations. For the viscosity (Pa.s), only 2EM had higher values (1.60 ± 0.15) in comparison with all monomers. In conclusion, polymerization kinetics was affected by the photoinitiators for both monomers. Viscosity was significantly increased with the use of secondary methacrylamide. SIGNIFICANCE: this work demonstrated the feasibility of using newly-synthesized methacrylamide monomers in conjunction with a series of initiator systems already used in commercial materials.


Asunto(s)
Cementos Dentales , Metacrilatos , Acrilamidas , Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Ensayo de Materiales , Fotoiniciadores Dentales , Polimerizacion
10.
Dent Mater ; 36(4): 542-550, 2020 04.
Artículo en Inglés | MEDLINE | ID: mdl-32061442

RESUMEN

OBJECTIVE: The use of the BisGMA as base monomer in dental composites has been questioned because of bisphenol A (BPA) is used as raw material in its synthesis, and BPA possess estrogenic potential associated to several health problems. This study describes the synthesis of the trimethacrylate tris(4-hydroxyphenyl)methane triglycidyl methacrylate (TTM) monomer and evaluate its effect when used as base monomer in the formulation of experimental photopolymerizable composite resins. METHODS: The TTM monomer was synthesized by a nucleophilic acyl substitution. Its chemical structure was confirmed via 1H and 13C NMR spectroscopy and FTIR spectroscopy. Experimental composite resins were formulated by mixing TTM, triethyleneglycol dimethacrylate (TEGDMA) and inorganic fillers. A BisGMA/TEGDMA based composite resin was prepared and used as control to compare several physicochemical properties. Cell viability assay was used for cytotoxicity evaluation. RESULTS: TTM was successfully synthesized with quantitative yields. The results showed that the TTM-based composite resin had similar values of flexural strength, elastic modulus, degree of conversion and polymerization shrinkage than the control (p > 0.05). Water sorption and solubility were statistically significantly higher than the control (p < 0.05), however they complied the requirements stablished by the ISO 4049. Finally, this study shows there were no statistically significant differences for the biocompatibility outcomes (p = 0.345). SIGNIFICANCE: TTM monomer could be potentially useful in the formulation of BisGMA free composite resins, which could mean to minimize the human exposure to BPA.


Asunto(s)
Resinas Compuestas , Ácidos Polimetacrílicos , Bisfenol A Glicidil Metacrilato , Resistencia Flexional , Humanos , Ensayo de Materiales , Metacrilatos , Polietilenglicoles , Polimerizacion , Solubilidad
11.
Braz Oral Res ; 34: e005, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32022224

RESUMEN

The purpose of this study was to evaluate the effect of ionizing radiation from high energy X-ray on fluoride release, surface roughness, flexural strength, and surface chemical composition of the materials. The study groups comprised five different restorative materials: Beautifil II, GCP Glass Fill, Amalgomer CR, Zirconomer, and Fuji IX GP. Twenty disk-shaped specimens (8x2 mm) for fluoride release and 20 bar-shaped specimens (25 x 2x 2 mm) for flexural strength were prepared from each material. Each material group was divided into two subgroups: irradiated (IR) and non-irradiated (Non-IR). The specimens from IR groups were irradiated with 1.8 Gy/day for 39 days (total IR = 70.2 Gy). The amount of fluoride released into deionized water was measured using a fluoride ion-selective electrode and ion analyzer after 24 hours and on days 2, 3, 7, 15, 21, 28, 35, and 39 (n = 10). The flexural strength was evaluated using the three-point bending test (n = 10). After the period of measurement of fluoride release, seven specimens (n = 7) from each group were randomly selected to evaluate surface roughness using AFM and one specimen was randomly selected for the SEM and EDS analyses. Data were analyzed with two-way ANOVA and Tukey tests (p = 0.05). The irradiation significantly increased fluoride release and surface roughness for Amalgomer CR and Zirconomer groups (p < 0.05). No significant change in flexural strength of the materials was observed after irradiation (p > 0.05). The ionizing radiation altered the amount of fluoride release and surface roughness of only Amalgomer CR and Zirconomer. The effect could be related to the chemical compositions of materials.


Asunto(s)
Apatitas/efectos de la radiación , Bisfenol A Glicidil Metacrilato/efectos de la radiación , Resinas Compuestas/efectos de la radiación , Fluoruros/química , Cementos de Ionómero Vitreo/efectos de la radiación , Radiación Ionizante , Circonio/efectos de la radiación , Análisis de Varianza , Apatitas/química , Bisfenol A Glicidil Metacrilato/química , Resinas Compuestas/química , Resistencia Flexional , Cementos de Ionómero Vitreo/química , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Valores de Referencia , Reproducibilidad de los Resultados , Espectrometría por Rayos X , Estadísticas no Paramétricas , Propiedades de Superficie/efectos de la radiación , Factores de Tiempo , Circonio/química
12.
J Phys Chem Lett ; 11(6): 2177-2181, 2020 Mar 19.
Artículo en Inglés | MEDLINE | ID: mdl-32109070

RESUMEN

Photoactivation in the Photoactive Yellow Protein, a bacterial blue-light photoreceptor, proceeds via photoisomerization of the double C═C bond in the covalently attached chromophore. Quantum chemistry calculations, however, have suggested that in addition to double-bond photoisomerization, the isolated chromophore and many of its analogues can isomerize around a single C-C bond as well. Whereas double-bond photoisomerization has been observed with X-ray crystallography, experimental evidence of single-bond photoisomerization is currently lacking. Therefore, we have synthesized a chromophore analogue, in which the formal double bond is covalently locked in a cyclopentenone ring, and carried out transient absorption spectroscopy experiments in combination with nonadiabatic molecular dynamics simulations to reveal that the locked chromophore isomerizes around the single bond upon photoactivation. Our work thus provides experimental evidence of single-bond photoisomerization in a photoactive yellow protein chromophore analogue and suggests that photoisomerization is not restricted to the double bonds in conjugated systems. This insight may be useful for designing light-driven molecular switches or motors.


Asunto(s)
Fotoquímica/métodos , Proteínas/química , Bisfenol A Glicidil Metacrilato , Humanos
13.
Dent Mater ; 36(3): 343-352, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-31924386

RESUMEN

OBJECTIVE: The structure of the polymer phase of dental resin-based-composites is highly sensitive to photo-polymerisation variables. The objective of this study was to understand how different polymer structures, generated with different photo-polymerisation protocols, respond to thermal perturbation. METHODS: Experimental resins were prepared from a series of Bis-GMA/TEGDMA blends (40/60, 50/50 and 60/40 wt.%), with either Camphorquinone/DMAEMA or Lucirin TPO as the photo-initiator system. Resins were photo-polymerised, in a disc geometry, at either relatively 'high' (3000 mW cm-2 for 6 s) or 'low' (300 mW cm-2 for 60 s) irradiances ensuring matched radiant exposures (18 J cm-2). Specimens were heated, from 20-160 °C at a rate of 5 °C min-1, whilst simultaneous synchrotron X-ray scattering measurements were taken at 5 °C increments to determine changes in polymer chain segment extension and medium-range order as a function of temperature. For each unique resin composition (n = 3), differential scanning calorimetry was used to measure glass transition temperatures using the same heating protocol. A paired t-test was used to determine significant differences in the glass transition temperature between irradiance protocols and photo-initiator chemistry at ɑ = 0.05. RESULTS: Resins pre-polymerised through the use of TPO and or high irradiances demonstrated a reduced rate of chain extension indicative of lower thermal expansion and a larger decrease in relative order when heated below the glass transition temperature. Above the transition temperature, differences in the rate of chain extension were negligible, but slower converted systems showed greater relative order. There was no significant difference in the glass transition temperature between different photo-initiator systems or irradiance protocols. SIGNIFICANCE: The evolution of chain extension and medium-range order during heating is dependent on the initial polymer structure which is influenced by photo-polymerisation variables. Less ordered systems, generated at faster rates of reactive group conversion displayed reduced chain extension below the glass transition temperature and maintained lower order throughout heating.


Asunto(s)
Resinas Compuestas , Resinas Sintéticas , Bisfenol A Glicidil Metacrilato , Ensayo de Materiales , Polietilenglicoles , Polimerizacion , Ácidos Polimetacrílicos , Resinas de Plantas , Temperatura
14.
Dent Mater ; 36(2): 310-319, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-31866065

RESUMEN

OBJECTIVE: To provide conditions for the validity of the exposure reciprocity law as it pertains to the photopolymerization of dimethacrylate-based dental composites. METHODS: Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMA and UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the composites used camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system. A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and a microprobe thermocouple was used to simultaneously measure the degree of conversion (DC), the polymerization stress (PS) due to the shrinkage, and the temperature change (TC) in real time during the photocuring process. The instrument has an integrated LED light curing unit providing irradiances ranging from 0.01W/cm2 to 4W/cm2 at a peak wavelength of 460nm (blue light). Vickers hardness of the composites was also measured. RESULTS: For every dental composite there exists a minimum radiant exposure required for an adequate polymerization (i.e., insignificant increase in polymerization with any further increase in the radiant exposure). This minimum predominantly depends on the resin viscosity of composite and can be predicted using an empirical equation established based on the test results. If the radiant exposure is above this minimum, the exposure reciprocity law is valid with respect to DC for high-fill composites (filler contents >50% by mass) while invalid for low-fill composites (that are clinically irrelevant). SIGNIFICANCE: The study promotes better understanding on the applicability of the exposure reciprocity law for dental composites. It also provides a guidance for altering the radiant exposure, with the clinically available curing light unit, needed to adequately cure the dental composite in question.


Asunto(s)
Resinas Compuestas , Materiales Dentales , Bisfenol A Glicidil Metacrilato , Ensayo de Materiales , Polimerizacion , Viscosidad
15.
Support Care Cancer ; 28(1): 239-247, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31020438

RESUMEN

OBJECTIVES: To evaluate the in vitro effects of radiotherapy (RT) on the morphological surface of the enamel and dentin and to determine the best adhesive system and most appropriate time to restore teeth in head and neck cancer patients. METHODS: Sixty third molars were cut into 120 enamel fragments and 120 dentin fragments and divided into four groups (n = 30): G1 (control): nonirradiated, only restorative procedure; G2: restorative procedure immediately before RT; G3: restorative procedure immediately after RT; and G4: restorative procedure 6 months after RT. Each group was divided into two subgroups: Adper™ Single Bond 2 (SB) and Clearfill SE Bond (CL) based on the material used. After RT and restorative procedures, the specimens were subjected to confocal microscopy and shear bond strength test. Data were analyzed using a two-way ANOVA followed by Tukey's test at a significance level of 5%. RESULTS: Morphological changes were observed in both substrates after a cumulative dose of 40 Gy, and after 60 Gy, the changes were more evident in both substrates. CL had the highest strength values in both substrates (p < 0.05), and G2 had the lowest strength values for the enamel and dentin (p < 0.05). CONCLUSIONS: Based on the in vitro study results, we can conclude that RT substantially changes the morphological surface of enamel and dentin and impairs the bond strength. The Clearfill system yielded better results than Adper Single Bond 2, and restoring teeth before RT resulted in the worst results in both substrates.


Asunto(s)
Adhesivos/efectos de la radiación , Esmalte Dental/efectos de la radiación , Recubrimientos Dentinarios/efectos de la radiación , Dentina/efectos de la radiación , Neoplasias de Cabeza y Cuello/radioterapia , Bisfenol A Glicidil Metacrilato/efectos de la radiación , Resinas Compuestas/efectos de la radiación , Recubrimiento Dental Adhesivo , Dentición Permanente , Neoplasias de Cabeza y Cuello/patología , Humanos , Ensayo de Materiales , Diente Molar/efectos de la radiación , Dosis de Radiación , Distribución Aleatoria , Cementos de Resina/efectos de la radiación , Resistencia al Corte/efectos de la radiación , Fracturas de los Dientes/etiología , Fracturas de los Dientes/patología
16.
J Prosthet Dent ; 123(2): 339-348, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31079889

RESUMEN

STATEMENT OF PROBLEM: Monomer leaching from restorations may affect the oral mucosa and general health; however, information on monomer leaching from chairside computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials is lacking. PURPOSE: The purpose of this in vitro study was to investigate the leaching of monomers from newly introduced resin-modified ceramics and composite resin CAD-CAM blocks that were immersed in water and ethanol for short-term and long-term incubation periods. MATERIAL AND METHODS: Ten square-shaped specimens of 5 newly introduced CAD-CAM blocks were suspended by means of a silk thread in distilled water and in 75% ethanol. After 1 day, 7 days, 30 days, and 60 days, the eluates bisphenol A (BPA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), N, N-dimethylacrylamide (DMA), bisphenol A-glycidyl dimethacrylate (Bis-GMA), and bisphenol A ethoxylate dimethacrylate (Bis-EMA) were analyzed by means of high-performance liquid chromatography (HPLC). Additional specimens of each material, before and after immersion in the solutions, were investigated by scanning electron microscopy, and elemental analysis was performed by energy-dispersive X-ray spectrometry. RESULTS: TEGDMA and UDMA were the main monomers eluted from all the materials tested. A pattern of declining release was detected for all the monomers. Bisphenol-A was not released by any of the investigated ceramic-composite or composite resin blocks either in water or ethanol. CONCLUSIONS: CAD-CAM blocks release less monomer when they are immersed in aqueous solutions in the short-term and long-term periods than conventional resin composite materials. The amount of monomer release declined until no monomer could be detected.


Asunto(s)
Cerámica , Resinas Compuestas , Bisfenol A Glicidil Metacrilato , Diseño Asistido por Computadora , Materiales Dentales , Ensayo de Materiales , Polietilenglicoles , Ácidos Polimetacrílicos
17.
Clin Oral Investig ; 24(1): 369-375, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31104114

RESUMEN

PURPOSE: To determine the effect of aging methods on the fracture toughness of a conventional Bis-GMA-based resin composite (Filtek Supreme), an ormocer-based resin composite (Admira), and an experimental hydrophobic oxirane/acrylate interpenetrating network resin system (OASys)-based composite. METHODS: A 25 × 5 × 2.8-mm stainless-steel mold with 2.5 mm single-edge center notch, following ASTM standards [E399-90], was used to fabricate 135 specimens (n = 15) of the composite materials and randomly distributed into groups. For the baseline group, specimens were fabricated and then tested after 24-h storage in water. For the biofilm challenge, specimens were randomly placed in a six-well tissue culture plate and kept at 37 °C with bacterial growth media (Brain Heart Infusion (BHI); Streptococcus mutans) changed daily for 15 days. For the water storage challenge, specimens were kept in 5 ml of deionized distilled autoclaved water for 30 days at 37 °C. µCT evaluation by scanning the specimens was performed before and after the proposed challenge. Fracture toughness (KIc) testing was carried out following the challenges. RESULTS: µCT surface area and volume analyses showed no significant changes regardless of the materials tested or the challenge. Filtek and Admira fracture toughness was significantly lower after the biofilm and water storage challenges. OASys mean fracture toughness values after water aging were significantly higher than that of baseline. Toughness values for OASys composites after biofilm aging were not statistically different when compared to either water or baseline values. CONCLUSION: The fracture toughness of Bis-GMA and ormocer-based dental resin composites significantly decreased under water and bacterial biofilm assault. However, such degradation in fracture toughness was not visible in OASys-based composites. CLINICAL SIGNIFICANCE: Current commercial dental composites are affected by the oral environment, which might contribute to the long-term performance of these materials.


Asunto(s)
Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Óxido de Etileno , Cerámicas Modificadas Orgánicamente , Ensayo de Materiales , Propiedades de Superficie
18.
J Prosthet Dent ; 123(2): 349-354, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31202550

RESUMEN

STATEMENT OF PROBLEM: Three-dimensional printing has the potential for clinical applications, and additive manufacturing materials for dental use merit further investigation. PURPOSE: The purpose of this in vitro study was to evaluate the properties of materials formulated with ethoxylated bisphenol A-dimethacrylate (Bis-EMA), urethane dimethacrylate (UDMA), and triethylene glycol dimethacrylate (TEGDMA) as 3D printing resins for ultraviolet digital light processing (UV-DLP) 3D printers and to characterize the mechanical and biological properties and accuracy of the printed objects. MATERIAL AND METHODS: Ten different light-polymerized resins were formulated using Bis-EMA, UDMA, and TEGDMA. Their viscosities were measured, and only 7 resins with viscosities lower than 1500 centipoise (cP) were selected for 3D printing and further material characterization. The light-polymerized resins were printed into representative shapes using a custom-made 3D printer equipped with a 405-nm UV-DLP projector as the light source. The printed specimens were subjected to biologic, mechanical, and accuracy tests, and the data were submitted to 1-way ANOVA and Tukey post hoc comparisons (α=.05). RESULTS: Photopolymerizable resins made of Bis-EMA, UDMA, and TEGDMA were successfully formulated for 3D printing to fabricate objects of various shapes and sizes. TEGDMA served as the diluent to reduce the viscosity and increase the degree of conversion, while UDMA and Bis-EMA provided strength as demonstrated by the mechanical testing. All the printed objects passed cytotoxicity testing. The flexural strengths of the printed specimens ranged between 60 MPa and 90 MPa; flexural modulus ranged between 1.7 GPa and 2.1 GPa; and surface hardness ranged between 14.5 HV and 24.6 HV. These represent similar mechanical properties to those of currently used clinical resin materials. In the accuracy test, the resin mixture composed of 80% Bis-EMA, 10% UDMA, and 10% TEGDMA had the highest accuracy, with a 0.051-mm deviation from the original design. CONCLUSIONS: Bis-EMA, UDMA, and TEGDMA are good candidates for the formulation of 3D printing resins for dental use. The printed objects demonstrated favorable biological and mechanical properties. Further, the accuracy of the printed specimens showed potential for clinical application.


Asunto(s)
Resinas Compuestas , Ácidos Polimetacrílicos , Bisfenol A Glicidil Metacrilato , Ensayo de Materiales , Metacrilatos , Polietilenglicoles , Poliuretanos , Impresión Tridimensional
19.
Dent Mater ; 36(1): e15-e26, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31791735

RESUMEN

OBJECTIVE: The object is to find an easy but efficient way to illustrate the in-situ dispersion of nano-scaled one-dimensional fillers in composite resins, and to correlate their dispersion status with the properties of composite resins. METHODS: Fluorescent europium-doped hydroxyapatite nanowires (HANW:Eu) were synthesized via the hydrothermal method. The HANW:Eu was mixed into Bis-GMA/TEGDMA (60/40, w/w) at different contents (1-5wt.%), and different processing methods (kneading, grinding, stirring) were tested to achieve good dispersion of HANW:Eu with the aid of fluorescent imaging system. Then, the mixtures of HANW:Eu and barium glass powder (BaGP) were kneaded into resin at a fixed content (70wt.%) while at different mixing ratios. In addition to the 3D fluorescent imaging, characterizations were carried out on mechanical properties, fractured surface, wear resistance and polymerization shrinkage, to correlate the composite properties of with the dispersion status of the incorporated HANW:Eu. RESULTS: By doping calcium with 5mol.% of europium, the obtained HANW:Eu displayed strong fluorescence, which made the illustration of its in-situ dispersion status within composites being possible. And this helped to judge that kneading was more efficient to homogeneously disperse HANW:Eu than grinding and stirring. However, it was illustrated vividly that HANW:Eu aggregated severely when it was co-incorporated with BaGP into composites at the total content of 70wt.%, which had not been previously revealed by other microscope observations. In comparison with composites containing 70wt.% of BaGP, improvements in the mechanical properties of resulting composites were identified for the cases containing 3wt.% of HANW and 67wt.% of BaGP, however, their wear volume loss and the polymerization shrinkage did not decrease as expected due to the HANW aggregations. SIGNIFICANCE: The fluorescent filler prepared in this study provides a feasible strategy to illustrate the in-situ dispersion status of inorganic fillers, which provides guidance for the processing of composite resins.


Asunto(s)
Durapatita , Nanocables , Bisfenol A Glicidil Metacrilato , Resinas Compuestas , Europio , Ensayo de Materiales , Polietilenglicoles , Ácidos Polimetacrílicos , Propiedades de Superficie
20.
Dent Mater ; 36(1): 157-166, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31791739

RESUMEN

OBJECTIVE: Although bisphenol A-glycidyl methacrylate (Bis-GMA)-based dental materials are widely used in dentistry, Estrogenicity from released bisphenol A remains a concern due to possibility of adversely affecting the growth of children and homeostasis of adults. Here, a new family of isosorbide-derived biomonomers were synthesized and experimentally utilized as a matrix of dental sealants to provide physico-mechanical and biological properties comparable to those of a conventional Bis-GMA-based material but without the the potential estrogenicity. METHODS: After synthesis of isosorbide-derived biomonomers (ISDB) by light polymerization, an experimental dental sealant with different silica filler concentrations (0-15wt%) was characterized and compared to a commercially available Bis-GMA-based sealant. Cytotoxicity and estrogenicity assays were conducted with human oral keratinocytes and estrogen-sensitive MCF-7 cells, respectively. RESULTS: ISDB-based dental sealants exhibited typical initially smooth surfaces with depth of cure, Vickers hardness, compressive strength/modulus, water resorption/solubility, and flowability comparable to those of the commercial sealant and met the ISO standard for dental sealants and polymer-based restorative materials. Indirect cytotoxicity tests using an extract showed comparable viability among experimental ISDB-based materials and a commercial Bis-GMA-incorporated control. DNA synthesis in MCF-7 cells (a marker of estrogenicity) and the release of bisphenol A under enzymatic incubation were not detected in ISDB-based materials. SIGNIFICANCE: In conclusion, the comparable physico-mechanical properties of ISDB-based materials with their cytocompatibility and lack of estrogenicity suggest the potential usefulness of ISDBs as a newly developed and safe biomaterial.


Asunto(s)
Polietilenglicoles , Ácidos Polimetacrílicos , Adulto , Biopolímeros , Bisfenol A Glicidil Metacrilato , Niño , Resinas Compuestas , Humanos , Ensayo de Materiales , Polimerizacion
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