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1.
Int J Mol Sci ; 22(9)2021 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-33946824

RESUMEN

Red blood cells (RBCs) serve a variety of functions beyond mere oxygen transport both in health and pathology. Notably, RRx-001, a minimally toxic pleiotropic anticancer agent with macrophage activating and vascular normalization properties currently in Phase III trials, induces modification to RBCs which could promote vascular adhesion similar to sickle cells. This study assessed whether RBCs exposed to RRx-001 adhere to the tumor microvasculature and whether this adhesion alters tumor viability. We next investigated the biomechanics of RBC adhesion in the context of local inflammatory cytokines after treatment with RRx-001 as a potential mechanism for preferential tumor aggregation. Human HEP-G2 and HT-29 tumor cells were subcutaneously implanted into nu/nu mice and were infused with RRx-001-treated and Technetium-99m (99mTc)-labeled blood. RBC adhesion was quantified in an in vitro human umbilical vein endothelial cell (HUVEC) assay under both normoxic and hypoxic conditions with administration of either lipopolysaccharide (LPS) or Tumor necrosis alpha (TNFα) to mimic the known inflammation in the tumor microenvironment. One hour following administration of 99mTc labeled RBCs treated with 10 mg/kg RRx-001, we observed an approximate 2.0-fold and 1.5-fold increase in 99mTc-labeled RBCs compared to vehicle control in HEPG2 and HT-29 tumor models, respectively. Furthermore, we observed an approximate 40% and 36% decrease in HEP-G2 and HT-29 tumor weight, respectively, following treatment with RRx-001. To quantify RBC adhesive potential, we determined τ50, or the shear stress required for 50% disassociation of RBCs from HUVECs. After administration of TNF-α under normoxia, τ50 was determined to be 4.5 dynes/cm2 (95% CI: 4.3-4.7 dynes/cm2) for RBCs treated with 10 µM RRx-001, which was significantly different (p < 0.05) from τ50 in the absence of treatment. Under hypoxic conditions, the difference of τ50 with (4.8 dynes/cm2; 95% CI: 4.6-5.1 dynes/cm2) and without (2.6 dynes/cm2; 95% CI: 2.4-2.8 dynes/cm2) 10 µM RRx-001 treatment was exacerbated (p = 0.05). In conclusion, we demonstrated that RBCs treated with RRx-001 preferentially aggregate in HEP-G2 and HT-29 tumors, likely due to interactions between RRx-001 and cysteine residues within RBCs. Furthermore, RRx-001 treated RBCs demonstrated increased adhesive potential to endothelial cells upon introduction of TNF-α and hypoxia suggesting that RRx-001 may induce preferential adhesion in the tumor but not in other tissues with endothelial dysfunction due to conditions prevalent in older cancer patients such as heart disease or diabetic vasculopathy.


Asunto(s)
Antineoplásicos/farmacología , Azetidinas/farmacología , Células Endoteliales/citología , Membrana Eritrocítica/efectos de los fármacos , Nitrocompuestos/farmacología , Animales , Antineoplásicos/uso terapéutico , Azetidinas/uso terapéutico , Adhesión Celular/efectos de los fármacos , Hipoxia de la Célula , Cisteína/química , Citocinas/metabolismo , Células Endoteliales/química , Agregación Eritrocitaria/efectos de los fármacos , Membrana Eritrocítica/química , Células HT29/trasplante , Células Hep G2/trasplante , Células Endoteliales de la Vena Umbilical Humana , Humanos , Lipopolisacáridos/farmacología , Lípidos de la Membrana/biosíntesis , Ratones , Ratones Desnudos , Neoplasias/irrigación sanguínea , Neoplasias Experimentales/irrigación sanguínea , Neoplasias Experimentales/tratamiento farmacológico , Nitrocompuestos/uso terapéutico , Fosfatidilserinas/biosíntesis , Receptores de Superficie Celular/biosíntesis , Resistencia al Corte , Microambiente Tumoral , Factor de Necrosis Tumoral alfa/farmacología
2.
Dent Med Probl ; 58(1): 107-113, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33847469

RESUMEN

BACKGROUND: Considering the use of silane-containing universal adhesives to enhance the repair bond strength of porcelain restorations, a question arises whether the application of these adhesives eliminates the need for a separate application of silane or not. OBJECTIVES: This study aimed to assess the effect of various kinds of surface treatment, including hydrofluoric acid (HF) etching, the application of bis-silane and the use of universal adhesives, on the repair bond strength of feldspathic porcelain. MATERIAL AND METHODS: In this experimental in vitro study, 70 porcelain disks were fabricated and divided into 7 groups (n = 10) for the following types of surface treatment: C (control group) ­ HF etching + silane + Porcelain Bond; HSB ­ HF etching + Single Bond; HSSB ­ HF etching + silane + Single Bond; HAB ­ HF etching + All Bond; HSAB ­ HF etching + silane + All Bond; HFB ­ HF etching + FuturaBond®; and HSFB ­ HF etching + silane + FuturaBond. After applying different kinds of surface treatment, the specimens were light-cured and the Filtek® Z250 composite was bonded to the treated surfaces. The specimens were incubated in distilled water at 37°C for 24 h, and then underwent 5,000 thermal cycles. The repair bond strength of porcelain was measured and the mode of failure was determined under a stereomicroscope. Data was analyzed using the one-way analysis of variance (ANOVA) and Tukey's test. RESULTS: Differences between the groups in the porcelain repair bond strength were significant (p < 0.0001). Bond strength for Single Bond (p < 0.001) and All Bond (p < 0.001) along with silane was significantly higher than for the application of these adhesives without a separate silane application step. This difference was not significant for FuturaBond. Mixed failure was the dominant mode of failure in all groups. CONCLUSIONS: The application of silane, irrespective of the use of universal adhesives with or without silane, increased the porcelain repair bond strength. Thus, a separate silane application step following HF etching and the use of universal adhesives with or without silane can enhance the repair bond strength of feldspathic porcelain.


Asunto(s)
Recubrimiento Dental Adhesivo , Porcelana Dental , Grabado Ácido Dental , Humanos , Ensayo de Materiales , Cementos de Resina , Resistencia al Corte , Propiedades de Superficie
3.
Dent Mater J ; 40(3): 781-791, 2021 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-33814532

RESUMEN

To evaluate the bonding reliability of a universal adhesive compared to a commercial ceramic repair system for metal-ceramic cracks. In vitro part: sixty specimens with porcelain, metal and porcelain-metal substrate were fabricated. Half specimens were bonded by Singlebond Universal adhesive and Filtek Z350 resin composite. The other were processed by Ceramic Repair N. Shear bond strength was tested. In vivo part: forty patients with sixty ceramic fractured porcelain-fused-metal restorations were involved. Half were repaired by Singlebond Universal and Filtek Z350. The other were restored by Ceramic Repair N. The mean observation period was 65 weeks. Results showed the bond strength ranged from 13.97 MPa to 15.85 MPa using two different repair system on different substrate with no statistical difference. There was no statistical difference between the two adhesive system in survival rate according to Kaplan-Meier analysis. The universal adhesive had a similar repair performance compared to commercial ceramic repair system.


Asunto(s)
Recubrimiento Dental Adhesivo , Cerámica , Resinas Compuestas , Cementos Dentales , Porcelana Dental , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Reproducibilidad de los Resultados , Cementos de Resina , Resistencia al Corte , Propiedades de Superficie
4.
Biomed Res Int ; 2021: 6635963, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33928154

RESUMEN

Background: Baveno VI criteria, based on liver stiffness (LS) measured by transient elastography and platelet counts (PLT), have been proposed to avoid unnecessary endoscopy screening for high-risk varices (HRVs). However, the cut-off value of LS measured by 2D-SWE and PLT to predict HRVs in compensated hepatitis B-related cirrhotic patients remains unknown. Aims: To prospectively analyze the cut-off of the combination of LS measured by 2D-SWE and PLT in predicting HRVs and the influence of antiviral therapies in its efficacy. Methods: Serum parameters, LS, and endoscopy results were obtained from 160 compensated hepatitis B-related cirrhotic patients. The accuracy of the combined algorithm was assessed in the whole cohort and subgroups with or without consecutive antiviral therapies in the past 6 months. Results: In the whole cohort, the optimal cut-off value of LS for HRVs was 14.5 kPa. Patients with a LS value < 14.5 kPa with a PLT value > 110 × 109/L can be excluded from HRVs (NPV = 0.99, endoscopy saved rates = 0.68). Conversely, a LS value of ≥14.5 kPa and a PLT value of ≤110 × 109/L indicated HRVs, with accurate rates of 82.35%, and 10.63% of patients can avoid additional endoscopy screening. Moreover, antiviral therapy had no significant effect on the accuracy and rates saved from further endoscopy screening, when comparing patients with or without antiviral therapies (all p values > 0.05). Conclusions: The combination of LS (14.5 kPa) measured by 2D-SWE and PLT (110 × 109/L) can predict HRVs accurately in compensated hepatitis B-related cirrhotic patients without significant interference of antiviral therapy histories.


Asunto(s)
Diagnóstico por Imagen de Elasticidad , Várices Esofágicas y Gástricas/sangre , Várices Esofágicas y Gástricas/diagnóstico por imagen , Hepatitis B/sangre , Hepatitis B/complicaciones , Cirrosis Hepática/sangre , Cirrosis Hepática/complicaciones , Resistencia al Corte , Algoritmos , Antivirales/farmacología , Antivirales/uso terapéutico , Várices Esofágicas y Gástricas/fisiopatología , Femenino , Hepatitis B/diagnóstico por imagen , Hepatitis B/fisiopatología , Humanos , Hígado/fisiopatología , Cirrosis Hepática/diagnóstico por imagen , Cirrosis Hepática/fisiopatología , Masculino , Persona de Mediana Edad , Recuento de Plaquetas , Factores de Riesgo
5.
J Mech Behav Biomed Mater ; 119: 104498, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-33839538

RESUMEN

OBJECTIVE: In this study, we incorporated hybrid nanoparticles (poly (acrylic acid)-grafted nanoclay/nanosilica, respectively, with platelet and spherical morphologies, abbreviated as PAA-g-NC-Sil) in different concentrations (0, 0.2, 0.5, 1, 2 and 5 wt%) to an experimental dentin bonding system and investigated the physical properties of the filled adhesive and its shear bond strength (µ-SBS) to dentin. We subsequently compared the properties of the adhesives containing PAA-g-NC-Sil with previously studied adhesives containing poly (methacrylic acid)-g-nanoclay (PMA-g-NC) (Solhi et al., 2012a), poly (acrylic acid)-g-nanoclay (PAA-g-NC) (Solhi et al., 2012b), and the hybrid poly (methacrylic acid)-grafted-nanoclay-nanosilica (PMA-g-NC-Sil) (Solhi et al., 2020). MATERIALS AND METHODS: In a set of previous publications and the present paper, we grafted poly (acrylic acid) (PAA) or poly (methacrylic acid) (PMA) onto the surface of pristine Na-MMT nanoclay (Cloisite® Na+) through free radical polymerization of monomer in an aqueous media in the presence or absence of nanosilica particles. We characterized the resulting modified nanoparticles (PMA-g-NC, PAA-g-NC, PMA-g-NC-Sil and PAA-g-NC-Sil) using GPC, FTIR, TGA, and XRD. We then incorporated the modified particles as functionalized fillers to experimental dentin adhesives in different concentrations and studied the stability of modified fillers dispersion by separation analysis. We also studied the properties of the photo-cured adhesive matrices using FTIR, TEM, SEM, EDXA, and XRD. We examined the shear bond strength of the adhesives (containing different contents of each modified filler, separately) to human premolar teeth. The results were analysed and compared statistically. RESULTS: The results confirmed that the polymers have been grafted onto the surface of nanoclay. An exfoliated structure for the nanoclay platelets in the photo-cured adhesive containing PAA-g-NC-Sil was observed. Addition of 0.5 wt% of PAA-g-NC-Sil to the experimental adhesive increased the shear bond strength and the dispersion stability in comparison to unfilled adhesive. The same trend was also observed for adhesives containing PMA-g-NC, PAA-g-NC, and PMA-g-NC-Sil. The adhesive containing PAA-g-NC-Sil showed the best dispersion stability and subsequently the highest shear bond strength in the optimal concentration among adhesives containing the four available fillers (PMA-g-NC, PAA-g-NC, PMA-g-NC-Sil and PAA-g-NC-Sil). SIGNIFICANCE: Addition of poly (acrylic acid) modified nanoparticles to the experimental dentin adhesives resulted in higher shear bond strength due to the potential interactions between the carboxylic acid functional groups on the surface of the modified particles and the dentin structure. Between the poly (acrylic acid) and poly (methacrylic acid), the former acid with higher PKa performed better. Addition of the spherical nanosilica particles to the adhesives containing platelet nanoclay helped to better exfoliate the platelets resulting in improved µ-SBS and dispersion stability.


Asunto(s)
Recubrimiento Dental Adhesivo , Nanopartículas , Adhesivos , Cementos Dentales , Dentina , Recubrimientos Dentinarios , Humanos , Ensayo de Materiales , Polimerizacion , Cementos de Resina , Resistencia al Corte
6.
J Adhes Dent ; 23(2): 145-158, 2021 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-33825428

RESUMEN

PURPOSE: To investigate the impact of pretreatment and conditioning on shear bond strength (SBS), surface free energy (SFE) and surface roughness (SR) between polyetheretherketone (PEEK) and cold-cured polymethylmethacrylate (PMMA). MATERIALS AND METHODS: PEEK substrates (Dentokeep PEEK Disc, nt-trading) were air abraded with Al2O3 particles of different grain sizes applied with varying pressure at 1) 0.2 MPa - 50 µm Al2O3; 2) 0.4 MPa - 50 µm Al2O3; 3) 0.2 MPa - 110 µm Al2O3; 4) 0.4 MPa - 110 µm Al2O3; or 5) without air abrasion (n = 172/group). Surface properties were quantified using SFE and SR (n = 10/group), and scanning electron microscope imaging (n = 2/group). Substrates were conditioned with a) Visio.link (VL, Bredent); b) Scotchbond Universal (SU, 3M Oral Care); c) Bonding Fluid (BF, Schütz Dental); or d) without conditioning (WC; n = 40/subgroup) and bonded to the polymer (Futura Jet, Schütz Dental). SBS and fracture types were determined before and after 10,000 thermal cycles (n = 20/subgroup). Univariate ANOVA, Kruskal-Wallis test, Mann-Whitney U-test, Kaplan-Meier survival estimates, and Weibull distribution were computed (p < 0.05). Ciba-Geigy tables and the chi-squared test were used to analyze fracture type distributions. RESULTS: An increase in particle size and pressure resulted in similar or increased SBS, Weibull characteristic strength, and Weibull moduli (p < 0.001 - 0.046). The lowest results were observed for the control group (without air abrasion), while pretreatment with 0.4 MPa - 110 µm Al2O3 presented the highest values (p < 0.001). In comparison with the other conditioning procedures, VL showed high (p < 0.001 - 0.03), and SU and WC low SBS (p < 0.001 - 0.006). Although it did not influence SFE, an increase in particle size and pressure led to an increased SR (p < 0.001). CONCLUSION: Pretreatment with 0.4 MPa - 110 µm Al2O3 can be recommended to increase bonding properties between PEEK and PMMA. Application of adhesives such as VL can enhance SBS further.


Asunto(s)
Recubrimiento Dental Adhesivo , Polimetil Metacrilato , Abrasión Dental por Aire , Análisis del Estrés Dental , Dentaduras , Cetonas , Ensayo de Materiales , Polietilenglicoles , Cementos de Resina , Resistencia al Corte , Propiedades de Superficie
7.
Eur J Oral Sci ; 129(2): e12772, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33829577

RESUMEN

This study aimed to investigate the effect of universal adhesive and silane pretreatment on the bond durability of metal brackets to dental glass ceramics. Eighty lithium disilicate glass ceramic specimens were randomly assigned to one of four groups (n = 20) defined by the pretreatment and adhesive used: (i) Adper Single Bond 2; (ii) silane + Adper Single Bond 2; (iii) Single Bond Universal; and (iv) silane +Single Bond Universal. Maxillary central incisor metal brackets were bonded on the ceramic surfaces with resin composite. A shear bond strength test was conducted after 24 h of water storage and after 10,000 thermocycles. Adhesive remnant index scoring and field-emission scanning electron microscopy were performed to determine adhesives remaining on the ceramic surfaces and the ceramic ultrastructure following bracket debonding, respectively. After 10,000 thermocycles, specimens treated with Single Bond Universal preserved an appropriate bond strength between brackets and glass ceramics and showed minimum ceramic surface damage following bracket debonding, which was not the case in the other three groups. The application of a silane-containing universal adhesive without silane pretreatment achieves adequate durability of the bond of metal brackets to dental glass ceramics and allows safe debonding, which may aid in optimizing the effectiveness for orthodontic treatment.


Asunto(s)
Recubrimiento Dental Adhesivo , Soportes Ortodóncicos , Cerámica , Análisis del Estrés Dental , Ensayo de Materiales , Cementos de Resina , Resistencia al Corte , Silanos , Propiedades de Superficie
8.
Braz Dent J ; 32(1): 85-90, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33914007

RESUMEN

This study evaluated the chemical composition and microhardness of human enamel treated with an Enamel Matrix Derivative (EMD) solution, and the bond strength between composite resin and this enamel. Thirty human enamel samples were randomly divided into three groups: Untouched Enamel (UE), Demineralized Enamel (DE) and Demineralized Enamel Treated with EMD (ET). DE and ET groups were subjected to acid challenge and ET treated with EMD (EMD was directly applied over conditioned enamel and left for 15 min). Samples from each group (n=4) had chemical composition assessed through to attenuated total reflectance Fourier transform infrared (ATR-FTIR). Knoop microhardness of enamel samples from each group (n=10) was measured. For the microshear bond strength, the samples were etched for 30 s, and the adhesive was applied and cured for 10 s. Two matrixes were placed on the samples, filled with Filtek Z350 XT composite and cured for 20 s, each. The matrix was removed, and the microshear bond strength of each group (n=10) was tested. Data were subjected to Kruskal-Wallis test (for microhardness), to analysis of variance and to Tukey's test (for microshear bond strength); (α=0.05). FTIR results have shown phosphate (hydroxyapatite indicator) in 900-1200 cm-1 bands in the UE and ET groups, which were different from the DE group. Microhardness and microshear analyses recorded higher statistical values for the UE and ET groups than for DE. EMD application to demineralized enamel seems to have remineralized the enamel; thus, the microhardness and bond strength was similar between UE and ET groups.


Asunto(s)
Recubrimiento Dental Adhesivo , Resinas Compuestas , Cementos Dentales , Esmalte Dental , Dureza , Humanos , Ensayo de Materiales , Cementos de Resina , Resistencia al Corte
9.
Int J Mol Sci ; 22(8)2021 Apr 14.
Artículo en Inglés | MEDLINE | ID: mdl-33919803

RESUMEN

The phase behaviour of soft colloids has attracted great attention due to the large variety of new phenomenologies emerging from their ability to pack at very high volume fractions. Here we report rheological measurements on interpenetrated polymer network microgels composed of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylic acid (PAAc) at fixed PAAc content as a function of weight concentration. We found three different rheological regimes characteristic of three different states: a Newtonian shear-thinning fluid, an attractive glass characterized by a yield stress, and a jamming state. We discuss the possible molecular mechanisms driving the formation of these states.


Asunto(s)
Resinas Acrílicas/química , Vidrio/química , Reología , Hidrodinámica , Resistencia al Corte , Estrés Mecánico
10.
Biomed Res Int ; 2021: 6634595, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33816623

RESUMEN

Background: Orthodontic patients are at high risk to develop caries. This study is introducing a clinical method detecting interfacial defects between ceramic brackets and enamel utilizing optical coherent tomography in addition to using the nanoleakage expression in vitro test. Methods: Transbond XT primer and moisture insensitive primer (MIP) were bonded to 75 human premolar enamel surfaces and divided into (XTD), (MIPD), and (MIPW) groups. The (XTD) and (MIPD) groups had ceramic brackets bonded to dry enamel surfaces using TransBond and moisture insensitive primers, respectively, while the (MIPW) samples were bonded to moist enamel using moisture insensitive primer. All specimens were examined under crosspolarization optical coherence tomography. Debonding forces of the brackets to 45 teeth (15 teeth/group). 30 bonded specimens (15 specimens/group) were cross-sectioned to detect the nanoleakage expression using scanning electron microscope equipped with energy-dispersive spectroscopy (SEM/EDS). The degree of conversion of the specimens in the experimental groups was tested using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR/ATR). Results: Optical coherence tomography detected the interfacial defects between the ceramic brackets and tooth structure. One way ANOVA showed that (XTD) and (MIPD) groups recorded significantly higher bond strength values and less nanoleakage expression when compared to MIPW (p > 0.05). Conclusions: Optical coherence tomography can be utilized to detect interfacial adhesive-tooth defects. Dry enamel surfaces improve the quality of the enamel/primer interface (200 words).


Asunto(s)
Diente Premolar , Esmalte Dental , Soportes Ortodóncicos , Cementos de Resina/química , Humanos , Resistencia al Corte , Espectrometría por Rayos X
11.
Biomed Res Int ; 2021: 5534294, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33869625

RESUMEN

Aim: Root canal filling materials have the tendency to inhibit adhesion of resin-based composites. This study was aimed at evaluating the effect of root canal filling materials and their solvents on the shear bond strength (SBS) of resin composite with the primary tooth dentin. Methods and Materials: Seventy-two intact anterior primary teeth were selected. Smooth dentinal surfaces were prepared to a minimum diameter of 3 mm and thickness of 1.5-2.0 mm. The samples were equally divided into six groups (n = 12). In group 1: control group, no root filling material; in group 2: Metapex, no solvent; in group 3: Metapex+ethanol solvent; in group 4: ZOE, no solvent; in group 5: ZOE+ethanol solvent; and in group 6: ZOE+orange oil solvent were applied. Then, dentin surfaces were etched, and composite restorations were placed and cured. The specimens were stored in distilled water at 37°C for 24 hours. SBS values were determined using a universal testing machine. Results: The SBS values of composite to dentin in groups 2 and 4 were significantly lower than those in the control group (P < 0.001). Cleansing of the specimens with 96% ethanol after removal of Metapex significantly increased the composite-dentin bond (P < 0.001). Applying ZOE, only orange oil solvent significantly increased the SBS of the composite to the primary tooth dentin (P = 0.01). Conclusion: To reduce the negative effects of endodontic root filling materials on the SBS of composite and primary tooth dentin, ethanol is a suitable solvent when Metapex is used, while orange oil might be a better choice than ethanol when applying ZOE.


Asunto(s)
Resinas Compuestas/química , Recubrimiento Dental Adhesivo , Dentina/efectos de los fármacos , Materiales de Obturación del Conducto Radicular/farmacología , Resistencia al Corte/efectos de los fármacos , Solventes/química , Diente Primario/química , Dentina/ultraestructura , Humanos , Propiedades de Superficie
12.
Gen Dent ; 69(3): 24-29, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33908874

RESUMEN

This study evaluated the failure load and the shear bond strength of 4 block materials indicated for computer-aided design/computer-aided manufacturing (CAD/CAM) of dental veneers: lithium disilicate, feldspathic ceramic, polymer-infiltrated ceramic, and nanohybrid composite. The tested hypothesis was that the material that combined an elastic modulus similar to that of enamel with the highest bond strength values would present the highest failure load. From prefabricated CAD/CAM blocks, disc-shaped specimens (6.0 × 0.7 mm; n = 10) and cylinders (2.4 × 2.5 mm; n = 10) were fabricated for load-to-failure and shear bond strength tests, respectively. Materials were adhesively bonded to flattened bovine enamel surfaces, stored in distilled water at 37°C for 90 days, and subjected to thermocycling (2000 cycles of 5°C to 55°C). Discs of restorative material were bonded to enamel and subjected to an increasing load that was applied perpendicular to the bonding interface until catastrophic failure occurred. A chisel was used to apply an increasing load parallel to the adhesive interface between the enamel and a cylinder of restorative material to measure shear bond strength. Data were subjected to a Weibull analysis and 1-way analysis of variance followed by a Tukey post hoc test (α = 0.05). The type of restorative material significantly affected the (mean [SD]) failure load when bonded to enamel (P = 0.006): polymer-infiltrated ceramic (1167.9 [310.2] N) = feldspathic ceramic (1115.0 [382.0] N) = nanohybrid composite (1067.3 [251.0] N) > lithium disilicate (786.2 [304.5] N). The type of restorative material also significantly affected the (mean [SD]) bond strength to enamel (P < 0.001): lithium disilicate (32.81 [11.19] MPa) = polymer-infiltrated ceramic (27.04 [7.65] MPa) > feldspathic ceramic (21.11 [9.16] MPa) > nanohybrid composite (9.08 [3.66] MPa). The polymer-infiltrated ceramic presented the best performance when bonded to enamel.


Asunto(s)
Recubrimiento Dental Adhesivo , Cementos de Resina , Animales , Bovinos , Cerámica , Esmalte Dental , Porcelana Dental , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Resistencia al Corte , Propiedades de Superficie
13.
Zhonghua Kou Qiang Yi Xue Za Zhi ; 56(4): 342-348, 2021 Apr 09.
Artículo en Chino | MEDLINE | ID: mdl-33832035

RESUMEN

Objective: To explore the effect of subpressure on the bonding strength of resin to polycrystalline particulates modified zirconia ceramic. Methods: One hundred and twenty pre-sintered zirconia discs were prepared and divided into the control group, the sandblasting group and the 30, 50, 70 s acid etching group (24 per group) by the random number table method. There was no additional treatment in the control group and sandblasting group before sinering. The 30, 50, and 70 s acid etching groups were immersed in HF for 30, 50, 70 s, respectively, and then they were placed into CaCl2 solution for 90 s and dipped in NaOH solution at 80 ℃ for 2 h. After sintering, the sandblasting group was subjected to sandblasting. The surface tomography and roughness were tested. According to whether subpressure was applied or not after the adhesives were applied, each group was randomly divided into two subgroups with a random number table: a subpressure subgroup and a normal pressure subgroup (12 per subgroup). Resin columns were bonded to these specimens. Shear bonding strength (SBS) test was conducted and the bonding interface, fracture surface and failure mode were analyzed. Results: The surface of control group was smooth, and its roughness was (0.24±0.11) µm. The rough surface was formed after sandblasting in the sandblasting group, and its roughness was (0.95±0.12) µm. The surface roughness of 30, 50, 70 s acid etching groups [(0.60±0.15), (1.04±0.11), (1.57±0.16) µm] increased as the HF immersion time prolonged, and the difference in surface roughness of zirconia specimens among each group was statistically significant (P<0.05). The SBS values between zirconia and resin of all the subpressure subgroups, namely: the control group, the sandblasting group, and the 30, 50, 70 s acid etching group [(13.56±1.19), (20.98±2.11), (17.37±2.44), (24.19±2.97), (21.36±2.16) MPa] were significantly stronger than those in the normal pressure subgroups, namely: the control group, sandblasting group, 30, 50, 70 s acid etching group [(10.74±0.93), (18.47±2.14), (14.81±1.54), (20.74±2.56), (17.75±2.54) MPa] (P<0.05). No obvious gaps and bubbles were observed in the bonding interfaces in subpressure subgroups. The proportion of mixed failure was significantly increased after applying subpressure (P<0.05). Conclusions: The subpressure can effectively enhance the bonding strength between the resin and polycrystalline particulates modified zirconia ceramic and improve the bonding effect.


Asunto(s)
Recubrimiento Dental Adhesivo , Cementos de Resina , Cerámica , Cementos Dentales , Porcelana Dental , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Resistencia al Corte , Propiedades de Superficie , Circonio
14.
Oper Dent ; 46(1): 107-115, 2021 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-33882140

RESUMEN

CLINICAL RELEVANCE: Use of zirconia primers with a low pH and a high acidic monomer concentration should be employed in combination with dual-cure resin cements that are less sensitive to an acidic environment. Primers with lower 10-MDP concentrations attain better outcomes.


Asunto(s)
Recubrimiento Dental Adhesivo , Cementos de Resina , Ensayo de Materiales , Metacrilatos , Resistencia al Corte , Propiedades de Superficie , Circonio
15.
Int J Prosthodont ; 34(2): 221-228, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33882568

RESUMEN

PURPOSE: To investigate whether high-level irradiance and short light exposure times with light-emitting diode (LED) curing units could provide bond strength comparable to halogen lights for ceramic laminate veneers (CLVs). MATERIALS AND METHODS: A total of 160 extracted human maxillary central incisors were prepared to receive CLVs (lithium disilicate) in shades A1 and A3.5. CLVs were luted with light-curing (LC) and dual-curing (DC) resin cements using four protocols: 3 seconds in extra power mode, 8 seconds in high power mode, or 10 seconds in standard mode with an LED unit, or 40 seconds with a conventional halogen light from all aspects (n = 10). Following thermal cycles, shear bond strength test was performed with a universal testing machine. Data were analyzed using one-way analysis of variance and post hoc Tukey test. Failure modes were classified under a stereomicroscope, and data were analyzed using Pearson chi-square test (P = .050). RESULTS: According to the intragroup comparison of different irradiation protocols, the mean shear bond strength of the A1-LC-10 group was found to be significantly higher than that of the A1-LChalogen group (P = .026). Shear bond strength values of the A1-LC-10 group and A3.5-LC-10 group were significantly higher than that of the A3.5-DC-10 group (P = .003). The A3.5-DC-3, A3.5-LC-3, and A1-DC-8 groups revealed the significantly most adhesive failures, and the A1-LC-8 group revealed the most mixed failures (P < .001). CONCLUSION: Both light and dark ceramic shades with LC cement combination responded the best to the standard mode of 10-second exposure time with LED application. However, with conventional halogen light application, the highest bond strength values were obtained with DC cement and light ceramic shade combination.


Asunto(s)
Luces de Curación Dental , Recubrimiento Dental Adhesivo , Cerámica , Análisis del Estrés Dental , Cementos de Ionómero Vitreo , Humanos , Curación por Luz de Adhesivos Dentales , Ensayo de Materiales , Cementos de Resina , Resistencia al Corte , Propiedades de Superficie
16.
Molecules ; 26(4)2021 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-33672935

RESUMEN

Neither the modified Bingham model nor the Herschel-Bulkley model can be used to characterize and calculate the performance of shear thickening of highly flowable mortar because of their incalculability of the rheological parameters. A new exponential rheological model was established to solve the characterization and calculation of shear thickening of the lubrication layer (highly flowable mortar) during the pumping of concrete in this paper. This new exponential rheological model has three rheological parameters, namely, yield stress, consistency coefficient, and consistency exponent. They can quantitatively describe the yield stress, differential viscosity, and shear thickening degree of highly flowable mortar. The calculating results of the rheological parameters of the newly established model for the mortars with different compositions showed that the consistency exponent of mortar decreased with the increase of its sand-binder ratio or the dosage of fly ash in the binder. This indicates that the shear thickening degree of mortar decreases. The consistency exponent of mortar initially decreases and subsequently increases with the increase in silica fume content or the dosage of the superplasticizer. It illustrates that the degree of the shear thickening of mortar initially decreased and subsequently increased. These varying patterns were confirmed by the rheological experiment of mortars.


Asunto(s)
Materiales de Construcción/análisis , Modelos Teóricos , Reología , Resistencia al Corte , Dinámicas no Lineales , Plastificantes/química , Rotación , Torque , Viscosidad
17.
Carbohydr Polym ; 260: 117751, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712121

RESUMEN

The breakdown and buildup mechanisms in concentrated cellulose nanocrystal (CNC) suspensions under shear and during relaxation upon cessation of shear were accessed by small-angle X-ray and light scattering combined with rheometry. The dynamic structural changes over nanometer to micrometer lengthscales were related to the well-known three-regime rheological behavior. In the shear-thinning regime I, the large liquid crystalline domains were progressively fragmented into micrometer-sized tactoids, with their cholesteric axis aligned perpendicular to the flow direction. The viscosity plateau of regime II was associated to a further disruption into submicrometer-sized elongated tactoids oriented along the velocity direction. At high shear rate, regime III corresponded to the parallel flow of individual CNCs along the velocity direction. Upon cessation of flow, the relaxation process occurred through a three-step buildup mechanisms: i) a fast reassembling of the individual CNCs into a nematic-like organization established up to micrometer lengthscales, ii) a slower formation of oriented large cholesteric domains, and iii) their isotropic redistribution.


Asunto(s)
Celulosa/química , Nanopartículas/química , Dispersión del Ángulo Pequeño , Difracción de Rayos X , Dispersión Dinámica de Luz , Cristales Líquidos/química , Reología , Resistencia al Corte , Viscosidad
18.
Carbohydr Polym ; 260: 117778, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712134

RESUMEN

To deal with serious environmental damage resulting from plastic packaging materials, biodegradable films using natural products have gained considerable attention. Here, we provide a simple, fast, and environmentally-friendly route to construct a biodegradable film using chitosan (CS), bacterial cellulose (BC), and curcumin (Cur). Composite films (CSn-BC-Cur) using CS with different molecular weights were investigated, and their water moisture content (MC), water solubility (WS), contact angle (CA), mechanical properties, barrier properties, and antioxidant properties were compared. The obtained films were characterized by SEM, XRD, and TGA. The results showed that chitosan with a higher molecular weight presented higher contact angles and mechanical properties, along with a lower moisture content, water vapor transmission rate, and oxygen transmission rate. Furthermore, when the composite film was placed in 95 % ethanol, it released active substances. The results suggest that these composite films can be used as promising materials for food packaging.


Asunto(s)
Celulosa/química , Quitosano/química , Curcumina/química , Embalaje de Alimentos , Antioxidantes/química , Resistencia al Corte , Solubilidad , Temperatura , Agua/química
19.
Molecules ; 26(5)2021 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-33652887

RESUMEN

Although several natural plants and mixtures have been known and used over the centuries for their antibacterial activity, few have been thoroughly explored in the field of dentistry. Thus, the aim of this study was to enhance the antimicrobial activity of a conventional glass ionomer cement (GIC) with natural plant extracts. The effect of this alteration on the bond strength and film thickness of glass ionomer cement was evaluated and related to an 0.5% chlorohexidine modified GIC. Olive leaves (Olea europaea), Fig tree (Ficus carica), and the leaves and roots of Miswak (Salvadora persica) were used to prepare an alcoholic extract mixture. The prepared extract mixture after the evaporation of the solvent was used to modify a freeze-dried glass ionomer cement at three different extracts: water mass ratios 1:2, 1:1, and 2:1. An 0.5% chlorhexidine diacetate powder was added to a conventional GIC for the preparation of a positive control group (CHX-GIC) for comparison. The bond strength to dentine was assessed using a material-testing machine at a cross head speed of 0.5 mm/min. Failure mode was analyzed using a stereomicroscope at 12× magnification. The cement film thickness was evaluated in accordance with ISO standard 9917-1. The minimum number of samples in each group was n = 10. Statistical analysis was performed using a Kruskal-Wallis test followed by Dunn's post hoc test for pairwise comparison. There was a statistically insignificant difference between the median shear bond strength (p = 0.046) of the control group (M = 3.4 MPa), and each of the CHX-GIC (M = 1.7 MPa), and the three plant modified groups of 1:2, 1:1, 2:1 (M = 5.1, 3.2, and 4.3 MPa, respectively). The CHX-GIC group showed statistically significant lower median values compared to the three plant-modified groups. Mixed and cohesive failure modes were predominant among all the tested groups. All the tested groups (p < 0.001) met the ISO standard of having less than 25 µm film thickness, with the 2:1 group (M = 24 µm) being statistically the highest among all the other groups. The plant extracts did not alter either the shear bond strength or the film thickness of the GIC and thus might represent a promising additive to GICs.


Asunto(s)
Antiinfecciosos/química , Cementos Dentales/química , Cementos de Ionómero Vitreo/química , Extractos Vegetales/farmacología , Antiinfecciosos/farmacología , Clorhexidina/química , Clorhexidina/farmacología , Cementos Dentales/farmacología , Dentina/química , Dentina/microbiología , Ficus/química , Cementos de Ionómero Vitreo/farmacología , Humanos , Ensayo de Materiales , Olea/química , Extractos Vegetales/química , Hojas de la Planta/química , Raíces de Plantas/química , Salvadoraceae/química , Resistencia al Corte , Propiedades de Superficie
20.
Eur J Oral Sci ; 129(2): e12773, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33724583

RESUMEN

This review compiles the literature on the antioxidants used after tooth bleaching with either low or high-concentrated carbamide and hydrogen peroxide to recover the bond strength. Antioxidants used in bleached teeth are mainly natural and non-enzymatic, except for catalase. Commonly, antioxidants are applied to remove any reactive oxygen species (ROS) residues left from bleaching gels, which adversely affect adhesive procedures, such as restorations or orthodontic brackets bonding. Even though sodium ascorbate, the most thoroughly investigated antioxidant, showed the most efficient bond strength recovery at 10% concentration, its performance depends on the type of solution and the application time. Natural extracts, such as proanthocyanidins and green tea, showed satisfactory results in the reversal of bond strength at 5% and 10% concentrations, respectively. Sodium ascorbyl phosphate, α-tocopherol, and catalase exhibited promising results, but further research is required. The adhesive system type plays an important role in the outcome of enamel bond strength after the antioxidant application. The postponement of either restorations or orthodontic brackets cementation following bleaching procedures seems to be efficiently replaced by antioxidant application prior to bonding procedures. However, the efficacy of using an antioxidant to recover bond strength depends on its type and application time.


Asunto(s)
Recubrimiento Dental Adhesivo , Blanqueamiento de Dientes , Antioxidantes , Cementos Dentales , Peróxidos , Resistencia al Corte , Urea
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