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1.
J Adhes Dent ; 23(3): 217-222, 2021 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-34060301

RESUMO

PURPOSE: To evaluate the push-out bond strength (PBS) of glass-fiber posts (GFP) in different root canal zones (cervical, middle, and apical), bonded with experimental simplified adhesives (ESAs) containing different initiator systems (camphorquinone [CQ] or phenylpropanodione [PPD]) with or without diphenyl iodonium hexafluorophosphate (DPI), in combination with a DPI-containing composite cement. MATERIALS AND METHODS: ESA blends were prepared with bisphenol glycidyl methacrylate (bis-GMA), triethylene glycol dimethacrylate (TEG-DMA), 1,3-glycerol dimethacrylate (GDMA), 2-hydroxyethyl methacrylate (HEMA), and ethanol, then divided into 12 experimental groups (n = 10) according to the initiator systems (CQ, PPD, or CQ + PPD) and the presence or absence of DPI. The roots of 120 extracted bovine incisors were prepared with #5 Largo drills and the GFP were cemented with each ESA and experimental composite cements containing 0.05 mol% of DPI. The push-out bond strength (PBS) test was performed after 24 h of storage. Failure patterns were analyzed under a stereomicroscope. Data were analyzed with split-plot two-way ANOVA and Tukey's test (α = 0.05). RESULTS: PBS was significantly higher for DPI-containing ESAs in all regions evaluated, with the group containing 0.5 CQ + 1 PPD + 0.5 DPI exhibiting the highest PBS. There was no statistically signficant difference among groups without DPI. Most failures were classified as adhesive at the cement-dentin interface. CONCLUSIONS: The combination of an adhesive and a composite cement containing DPI salt can improve GFP bonding to root dentin, even in the apical region.


Assuntos
Cimentos Dentários , Cimentos de Resina , Animais , Bis-Fenol A-Glicidil Metacrilato , Bovinos , Materiais Dentários , Cloreto de Sódio
2.
Dent Mater ; 37(3): 382-390, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33468405

RESUMO

OBJECTIVES: The two-component Camphorquinone (CQ)/aromatic amine system is well-established and clearly corresponds to the reference system used in all photopolymerizable dental adhesives and composites. However, this CQ/amine system still suffers from the presence of aromatic amines that can be referenced as toxic. Therefore, the aim of this work is to develop amine-free photoinitiating systems (PISs) for the polymerization of a representative dental methacrylate resins upon blue light irradiation. The proposed strategy is based on the in-silico design (by molecular modelling) of new hydrogen donors (amine-free) bearing a copolymerizable moiety (methacrylate functionality) to ensure their low migration/leaching properties from the synthesized polymer. The new proposed PISs are compared to the well-established CQ/amine system for the polymerization of different methacrylate blends upon exposure to a commercial blue dental LED centered at 477 nm. METHODS: Molecular orbitals calculations are used to design new hydrogen donors exhibiting low C-H bond dissociation energies. Based on this in-silico design, the syntheses of new co-initiators are reported here for the first time. Real-time FTIR experiments are used to monitor the photopolymerization profiles. Color indexes measurements were also carried out to investigate the bleaching properties of the new proposed systems. RESULTS: Three new co-initiators are proposed as alternatives to aromatic amines in dental materials in combination with camphorquinone. The performances of the new proposed amine-free PISs for the photopolymerization of thick (1.4 mm) samples of methacrylate upon exposure to a blue dental LED under air are excellent. Similar or better polymerization performances are obtained with the new proposed amine-free systems compared to those reached with the CQ/amine reference. Excellent bleaching properties are also found. The involved chemical mechanisms are investigated through molecular orbitals calculations.


Assuntos
Aminas , Hidrogênio , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Materiais Dentários , Cura Luminosa de Adesivos Dentários , Teste de Materiais , Metacrilatos , Polimerização
3.
Dent Mater ; 37(2): 351-358, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33357987

RESUMO

OBJECTIVES: To evaluate high refractive index methacrylates as diluents for the formulation of radiopaque esthetic bulk-fill composites. METHODS: 2-(4-Cumylphenoxy)ethyl methacrylate 1, 2-(2-phenylphenoxy)ethyl methacrylate 2 and 2-[2-(2-phenylphenoxy)ethoxy]ethyl methacrylate 3 were synthesized and characterized by 1H NMR spectroscopy. The reactivity of each monomer was studied using photo-DSC. Bulk-fill composites based on monomers 1-3 were formulated. Translucency (before and after light cure) was measured using a spectrophotometer. The depth of cure and the water sorption of these materials were determined according to ISO 4049. The flexural strength and modulus of elasticity were measured using a three-point bending setup, according to ISO 4049. The shrinkage force was assessed based on a method described by Watts et al. using a universal testing machine. RESULTS: Monomers 1-3 were easily synthesized in two steps. They exhibit a low viscosity and a high refractive index (1.553-1.573). Monofunctional methacrylates 1-3 were found to be more reactive than triethylene glycol dimethacrylate (TEGDMA). Bulk-fill composites based on these monomers were successfully prepared. They exhibit a high depth of cure and excellent esthetic properties (low transparency). These composites provide higher flexural modulus as well as lower water sorption than a corresponding material based on TEGDMA. Methacrylates 1 and 3 are particularly interesting as they led to composites showing lower shrinkage force. SIGNIFICANCE: Methacrylates 1-3 are promising diluents for the formulation of highly esthetic radiopaque bulk-fill composites.


Assuntos
Resinas Compostas , Refratometria , Bis-Fenol A-Glicidil Metacrilato , Materiais Dentários , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Polimerização , Ácidos Polimetacrílicos , Viscosidade
4.
Mater Sci Eng C Mater Biol Appl ; 118: 111535, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33255088

RESUMO

OBJECTIVES: The aim of this study was to modify the surface of fillers used in dental composites by the synthesis of two novel thiourethane oligomeric silanes, used to functionalize the silica-containing inorganic particles. Several thiourethane silane concentrations were tested during the silanization process to systematically assess the effect of silane coverage on experimental composite conversion, polymerization stress and fracture toughness. MATERIALS AND METHODS: Two different thiourethane silanes were synthesized based either on 1,6-hexanediol-diissocynate (HDDI), or 1,3-bis(1-isocyanato-1-methylethyl) benzene (BDI). Conventional 3-(Trimethoxysilyl)propyl methacrylate was used as the control. Glass fillers were silanized with 1, 2 or 4 wt% of each thiourethane silane, then evaluated by thermogravimetrical analysis. Photopolymerizable resin composites were prepared with Bis-GMA/UDMA/TEGDMA and 50 wt% silanized glass filler. Polymerization kinetics and degree of conversion were tested using Near-IR. Bioman was used to test polymerization stress. Data were analyzed with two-way ANOVA/Tukey's test (α = 5%). RESULTS: The mass of silane coupled to the filler increased with the concentrations of thiourethane in the silanizing solution, as expected. Thiourethane-containing groups exhibited significantly higher degree of conversion compared to control groups, except for BDI 4%. HDDI 4%, BDI 2% and BDI 4% showed significantly lower polymerization stress than control groups. HDDI 4% exhibited significantly higher fracture toughness. CONCLUSIONS AND CLINICAL SIGNIFICANCE: Novel filler functionalization with thiourethane silanes may be a promising alternative for improving dental composites properties by significantly increasing the degree of conversion, fracture toughness and reducing the polymerization stress.


Assuntos
Resinas Compostas , Ácidos Polimetacrílicos , Bis-Fenol A-Glicidil Metacrilato , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Silanos , Propriedades de Superfície
5.
J Dent ; 105: 103557, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33309805

RESUMO

OBJECTIVES: The study aims to synthesize two different types of nano-fillers based on zirconia (ZrO2), which was functionalized with graphene oxide (GO-ZrO2), and hydroxyapatite (HA-ZrO2), and to implement them in an experimental methacrylate matrix containing new dimethacrylic oligomers. METHODS: Nano-particles were synthesized via a modified Hummer's method and a sol-gel route. Bisphenol A-glycidyl methacrylate oligomers (Bis-GMA336[0-1]) were synthesized from an epoxy resin that reacted with methacrylic acid in the presence of a basic catalyst. Traditional dental glass-fillers (Barium oxide/BaO and Barium fluoride/BaF2) were synthesized to create an experimental resin-based composite (RBC) used as reference. Filler morphology was evaluated via Transmission Electron Microscopy. RBCs were characterised by real-time Fourier transform infrared spectroscopy (degree of cure/DC, polymerisation kinetics), real-time spectrometry (light transmittance), 3-point bending test (flexural strength and modulus, Weibull parameters), and depth-sensing indentation test (plastic and elastic deformation parameters). RESULTS: The synthesized nanohybrid fillers proved good dispersing performance. Mechanical properties and materials' reliability are within or above the mean values reported in the literature for RBCs. Addition of HA-ZrO2-fillers resulted in a decrease light transmission, DC and mechanical properties. Except for the HA-ZrO2 RBC, materials showed a high resistance to softening in solvent. CONCLUSIONS: The synthesis of GO-ZrO2 and HA-ZrO2 nanohybrid particles and their implementation in experimental RBCs has proven successful. Adjustments of the light transmission through suitable co-fillers in addition to GO-ZrO2 as well as adjustments of the amount of HA-ZrO2 are necessary to enable reduced curing time (<20 s). CLINICAL SIGNIFICANCE: The addition of nanofillers with tailor-made properties can help improving the performance of modern restoratives.


Assuntos
Resinas Compostas , Durapatita , Bis-Fenol A-Glicidil Metacrilato , Grafite , Teste de Materiais , Reprodutibilidade dos Testes , Propriedades de Superfície , Suporte de Carga , Zircônio
6.
Niger J Clin Pract ; 23(8): 1148-1154, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32788494

RESUMO

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.


Assuntos
Adesivos/química , Colagem Dentária/métodos , Adesivos Dentinários/química , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Glutaral , Humanos , Teste de Materiais/métodos , Dente Molar , Ácidos Polimetacrílicos , Cimentos de Resina/química , Resistência à Tração
7.
Braz Oral Res ; 34: e099, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785474

RESUMO

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.


Assuntos
Esmalte Dentário , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Módulo de Elasticidade , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Ácidos Polimetacrílicos , Viscosidade
8.
Dent Mater ; 36(7): 884-892, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32402514

RESUMO

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.


Assuntos
Resinas Compostas , Metacrilatos , Bis-Fenol A-Glicidil Metacrilato , Módulo de Elasticidade , Teste de Materiais , Polietilenoglicóis , Polimerização , Ácidos Polimetacrílicos
9.
Oper Dent ; 45(5): 547-555, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32352351

RESUMO

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.


Assuntos
Colagem Dentária , Adesivos Dentinários , Adesivos , Bis-Fenol A-Glicidil Metacrilato , Cimentos Dentários , Dentina , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração
10.
Am J Dent ; 33(2): 69-73, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32259410

RESUMO

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.


Assuntos
Infiltração Dentária , Selantes de Fossas e Fissuras , Bis-Fenol A-Glicidil Metacrilato , Dente Molar
11.
J Dent ; 94: 103306, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32112910

RESUMO

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.


Assuntos
Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Metacrilatos , Teste de Materiais , Fosfatos , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Zircônio
12.
Niger J Clin Pract ; 23(2): 165-171, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32031090

RESUMO

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.


Assuntos
Adesivos/farmacologia , Resinas Compostas , Corrosão Dentária , Restauração Dentária Permanente/métodos , Lasers Semicondutores/uso terapêutico , Colo do Dente , Adulto , Bis-Fenol A-Glicidil Metacrilato , Adaptação Marginal Dentária , Sensibilidade da Dentina , Adesivos Dentinários , Feminino , Seguimentos , Humanos , Lasers Semicondutores/efeitos adversos , Masculino , Pessoa de Meia-Idade
13.
Eur J Oral Sci ; 128(1): 89-99, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32032451

RESUMO

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.


Assuntos
Metacrilatos , Poliuretanos , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Colagem Dentária , Preparo da Cavidade Dentária , Infiltração Dentária , Adesivos Dentinários , Humanos , Teste de Materiais , Cimentos de Resina , Resistência à Tração
14.
Dent Mater ; 36(3): 468-477, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32005546

RESUMO

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.


Assuntos
Cimentos Dentários , Metacrilatos , Acrilamidas , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Teste de Materiais , Fotoiniciadores Dentários , Polimerização
15.
Dent Mater ; 36(4): 542-550, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32061442

RESUMO

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.


Assuntos
Resinas Compostas , Ácidos Polimetacrílicos , Bis-Fenol A-Glicidil Metacrilato , Resistência à Flexão , Humanos , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Polimerização , Solubilidade
16.
Braz Oral Res ; 34: e005, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32022224

RESUMO

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.


Assuntos
Apatitas/efeitos da radiação , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Resinas Compostas/efeitos da radiação , Fluoretos/química , Cimentos de Ionômeros de Vidro/efeitos da radiação , Radiação Ionizante , Zircônio/efeitos da radiação , Análise de Variância , Apatitas/química , Bis-Fenol A-Glicidil Metacrilato/química , Resinas Compostas/química , Resistência à Flexão , Cimentos de Ionômeros de Vidro/química , Teste de Materiais , Microscopia Eletrônica de Varredura , Valores de Referência , Reprodutibilidade dos Testes , Espectrometria por Raios X , Estatísticas não Paramétricas , Propriedades de Superfície/efeitos da radiação , Fatores de Tempo , Zircônio/química
17.
J Phys Chem Lett ; 11(6): 2177-2181, 2020 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-32109070

RESUMO

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.


Assuntos
Fotoquímica/métodos , Proteínas/química , Bis-Fenol A-Glicidil Metacrilato , Humanos
18.
Dent Mater ; 36(3): 343-352, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31924386

RESUMO

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.


Assuntos
Resinas Compostas , Resinas Sintéticas , Bis-Fenol A-Glicidil Metacrilato , Teste de Materiais , Polietilenoglicóis , Polimerização , Ácidos Polimetacrílicos , Resinas Vegetais , Temperatura
19.
Dent Mater ; 36(2): 310-319, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31866065

RESUMO

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.


Assuntos
Resinas Compostas , Materiais Dentários , Bis-Fenol A-Glicidil Metacrilato , Teste de Materiais , Polimerização , Viscosidade
20.
Support Care Cancer ; 28(1): 239-247, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31020438

RESUMO

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.


Assuntos
Adesivos/efeitos da radiação , Esmalte Dentário/efeitos da radiação , Adesivos Dentinários/efeitos da radiação , Dentina/efeitos da radiação , Neoplasias de Cabeça e Pescoço/radioterapia , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Resinas Compostas/efeitos da radiação , Colagem Dentária , Dentição Permanente , Neoplasias de Cabeça e Pescoço/patologia , Humanos , Teste de Materiais , Dente Molar/efeitos da radiação , Doses de Radiação , Distribuição Aleatória , Cimentos de Resina/efeitos da radiação , Resistência ao Cisalhamento/efeitos da radiação , Fraturas dos Dentes/etiologia , Fraturas dos Dentes/patologia
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