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1.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(4): 376-379, 2020 Aug 01.
Artigo em Chinês | MEDLINE | ID: mdl-32865354

RESUMO

OBJECTIVE: This study aimed to compare the effects of water storage treatment and thermal cycling on the shear bond strength (SBS) of three self-adhesive dual-cure resin cements. METHODS: Six cubic zirconia specimens with side length of 2 cm were obtained by cutting and sintering. Three self-adhering dual-cure resin cements (i.e., Clearfil SAC, RelyX U200, and Multilink Speed) were selected. According to their bonding modes, they were divided into three groups: direct bonding group (direct coating with resin cement), adhesive group (applying universal adhesives and then coating with resin cement), and primer group (applying Z-Prime Plus and then coating with resin cement). According to experimental conditions, each group was divided into two subgroups: subgroup a (water storage at 37 ℃ for 24 h) and subgroup b (thermalcycling for 5 000 times). SBS data were analyzed by one-way ANOVA by using SPSS 19.0 software (P<0.05). The fractured zirconia surface was observed under a stereomicroscope. RESULTS: After water storage for 24 h, the SBS of the adhesive group and the primer group of the three resin cements was higher than that of the direct adhesive group (P<0.05), but the difference in SBS between the adhesive group and the primer group was not significant (P>0.05). After thermalcycling, the SBS of the three types of resin cements decreased (P<0.05); the SBS of the adhesive group was higher than that of the direct adhesive group and the primer group (P<0.05). Fracture mode analysis revealed that the type Ⅲ fracture mode evidently increased after the thermalcycling treatment compared with the water storage treatment. CONCLUSIONS: The universal adhesives and the primer can improve the SBS of self-adhesive dual-cure resin cement in water storage at 37 ℃ for 24 h. The universal adhesives had a better bonding durability than the zirconia primer.


Assuntos
Colagem Dentária , Cimentos de Resina , Cerâmica , Cimentos Dentários , Análise do Estresse Dentário , Teste de Materiais , Resistência ao Cisalhamento , Propriedades de Superfície , Zircônio
2.
Head Face Med ; 16(1): 20, 2020 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-32891153

RESUMO

INTRODUCTION: Bond failure during fixed orthodontic treatment is a frequently occurring problem. As bracket rebonding is associated with reduced shear bond strength, the aim of the present investigation is to analyse the effect of different innovative rebonding systems to identify optimised rebonding protocols for orthodontic patient care. METHODS: Metallic brackets were bonded to the frontal enamel surfaces of 240 bovine lower incisors embedded in resin bases. Teeth were randomly divided into two major experimental groups: in group 1 a hydrophilic primer (Assure™ PLUS) was compared to commonly used orthodontic adhesives (Transbond XT™, BrackFix®, Grengloo™) and a zero control. In group 2 different rebonding systems were analysed using a hydrophilic primer (Assure™ PLUS), a methyl methacrylate-consisting primer (Plastic Conditioner) and a conventional adhesive (Transbond XT™). All teeth were tested for shear bond strength according to the DIN-13990 standard, the Adhesive Remnant Index and enamel fracture rate. RESULTS: The hydrophilic primer enhanced shear bond strength at first bonding (Assure™ PLUS 20.29 ± 4.95 MPa vs. Transbond XT™ 18.45 ± 2.57 MPa; BrackFix® 17 ± 5.2 MPa; Grengloo™ 19.08 ± 3.19 MPa; Meron 8.7 ± 3.9 MPa) and second bonding (Assure™ PLUS 16.76 ± 3.71 MPa vs. Transbond XT™ 13.06 ± 3.19 MPa). Using Plastic Conditioner did not seem to improve shear bond strength at rebonding (13.57 ± 2.94). When enamel etching was left out, required shear bond strength could not be achieved (Plastic Conditioner + Assure™ PLUS 8.12 ± 3.34 MPa; Plastic Conditioner: 3.7 ± 1.95 MPa). Hydrophilic priming systems showed decreased ARI-scores (second bonding: 2.63) and increased enamel fracture rates (first bonding: 55%; second bonding 21,05%). CONCLUSIONS: Based on the present study we found that rebonding strength could be compensated by the use of hydrophilic priming systems. The additional use of a methyl methacrylate-consisting primer does not seem to enhance shear bond strength. No etching approaches resulted in non-sufficient bond strength.


Assuntos
Condicionamento Ácido do Dente , Colagem Dentária , Braquetes Ortodônticos , Animais , Bovinos , Cimentos Dentários , Análise do Estresse Dentário , Humanos , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento
3.
Dental Press J Orthod ; 25(4): 59-67, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32965388

RESUMO

OBJECTIVE: To compare the effectiveness of the pretreatment with sandblasting and deproteinization with NaOCl on bond strength (SBS), in situ conversion degree (CD) of brackets in fluorotic enamel, and enamel etching pattern. METHODS: A total of 90 non-carious maxillary premolars were used. The teeth were then assigned to six experimental groups according to: enamel surface (sound and fluorotic enamel); surface treatment (Regular etch with 37% phosphoric acid [RE]; 5.2% sodium hypochlorite + phosphoric acid [NaOCl + RE]; sandblasting + phosphoric acid [sandblasting + RE]). After storage in distilled water (37°C/24h), the specimens were tested at 1 mm/min until failure (SBS). Enamel-resin cement interfaces were evaluated for CD using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data from SBS and in situ CD values were analyzed using ANOVA two-away and Tukey test (α=0.05). The enamel etching pattern was evaluated only qualitatively. RESULTS: For sound enamel, RE showed the highest SBS values, when compared to NaOCl + RE and Sandblasting + RE groups (p< 0.01). Regarding CD, only NaOCl + RE significantly compromised the mean DC, in comparison with other groups (p= 0.002). For fluorotic enamel, the Sandblasting + RE group significantly increased the mean SBS values, in comparison with RE group (p= 0.01) and no significant change was observed for CD (p> 0.52). CONCLUSIONS: The application of NaOCl or sandblasting associated to phosphoric acid improved the SBS of the brackets in fluorotic enamel without compromising the CD of the resin cement, with improving of enamel interprismatic conditioning.


Assuntos
Colagem Dentária , Braquetes Ortodônticos , Condicionamento Ácido do Dente , Cimentos Dentários , Esmalte Dentário , Teste de Materiais , Ácidos Fosfóricos , Cimentos de Resina , Resistência ao Cisalhamento , Propriedades de Superfície
4.
J Oral Sci ; 62(4): 444-448, 2020 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-32879159

RESUMO

PURPOSE: High-viscosity glass ionomer cements (HV-GICs) are reinforced with ultrafine, highly reactive glass particles, as well as a higher-molecular-weight polyalkenoic acid component. Silver diammine fluoride (SDF) is an agent with promising activity against active caries. The present study aimed to evaluate the shear bond strength (SBS) and interfacial morphology of a new HV-GIC bonded to dentin after treatment with various adhesive protocols including SDF. METHODS: HV-GIC cylinders were bonded to dentin after various surface treatments (6 groups, n = 22): water; polyalkenoic acid; SDF; SDF + potassium iodide (KI); SDF + KI + polyalkenoic acid; SDF + KI + two weeks of storage in water + polyalkenoic acid. For each group, 20 samples were tested for SBS after 48 h, and 2 samples were cut and subjected to environmental scanning electron microscopy (E-SEM) and energy-dispersive X-ray (EDX) analysis. RESULTS: No significant differences in SBS were found between any of the protocols tested. However, E-SEM and EDX images showed different interfaces when SDF was applied. CONCLUSION: SDF has no influence on the adhesion of HV-GIC to sound dentin and could potentially improve the cario-resistance of the dentin/HV-GIC interface.


Assuntos
Colagem Dentária , Cimentos de Ionômeros de Vidro , Amônia , Dentina , Fluoretos , Teste de Materiais , Resistência ao Cisalhamento , Compostos de Prata , Viscosidade
5.
Int J Prosthodont ; 33(5): 536-545, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32956435

RESUMO

PURPOSE: To evaluate the shear bond strength (SBS) and color stability (ΔE) of four ceramic veneers (VITA VM 9; VITA VM 13; VITA VMK 95; and IPS e.max Ceram) following repair with three different self-adhesive composite resins (Fusio Liquid Dentin; Constic; and Vertise Flow) and BISCO Intraoral Repair Kit + Filtek Supreme (BC + FS). MATERIALS AND METHODS: A total of 96 specimens were prepared per ceramic material, and each ceramic group was divided into subgroups according to testing method (32 specimens for color stability analysis and 64 specimens for SBS testing). ΔE and SBS (SBS1 = non-aged, SBS2 = thermally aged) values of the repaired specimens were calculated. One specimen from each of the thermally aged groups was investigated under scanning electron microscopy (SEM). Two-way ANOVA was used to analyze the mean ΔE, SBS1, and SBS2 values. The differences between SBS1 and SBS2 values were analyzed using independent-samples t test. RESULTS: The lowest ΔE values were calculated for Constic (P ≤ .05). The SBS2 values among all groups were lower than the SBS1 values (P ≤ .05). The lowest SBS2 values were observed for Vertise Flow (2.3 ± 1.47 MPa) (P ≤ .05) and were below the acceptable limit of 5 MPa. CONCLUSION: All of the investigated repair materials in combination with the ceramic veneers exhibited ΔE values that were higher than the clinically acceptable limits. Thermal aging negatively affected the SBS values in all groups (P ≤ .05). All tested self-adhesive composite resins, with the exception of Vertise Flow, could be used instead of a repair kit with flowable composite resin, especially in noncooperative patients, for the purpose of repairing chipping fractures for VITA VM 9, VITA VM 13, and VITA VMK 95 (P > .05).


Assuntos
Colagem Dentária , Cimentos Dentários , Resinas Acrílicas , Cerâmica , Cor , Resinas Compostas , Porcelana Dentária , Humanos , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento , Propriedades de Superfície
6.
J Dent Child (Chic) ; 87(2): 69-76, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32787999

RESUMO

Purpose: To evaluate the morphological alterations in enamel and dentin of primary teeth following radiotherapy (RT) and to determine the best adhesive technique and time to carry out restorative procedures.
Methods: Enamel and dentin fragments of primary teeth were randomly assigned into four groups (n=30): G1 (control)-non-irradiated, only restorative procedure; G2- restorative procedure immediately before RT; G3-restorative procedure 24 hours after RT; and G4-restorative procedure six months after RT. Each group was divided into one of two subgroups according to the adhesive system used for restoration: (1) AdperSingle Bond 2 (SB); and (2) ClearfillSE Bond (CL). The specimens were submitted to fractionated RT until they reached the final dose of 60 Gy. They were then subjected to confocal microscopy and the shear bond strength test. Data were analyzed using two-way analysis of variance followed by Tukey's tests ( α = five percent).
Results: Morphological changes were first observed in enamel and dentin after 40 Gy of irradiation. G4 bond strength values were similar to G1 in the CL and SB groups for enamel and in the CL group for dentin (P >0.05). G2 showed the lowest values for enamel and dentin (P <0.05). In G3, CL presented the highest strength values in enamel; for G4, the highest values were found in dentin (P <0.05).
Conclusions: Radiotherapy affected the morphological surface of enamel and dentin. The restorations placed immediately after RT had the weakest shear bond strength, and the restorations placed six months after RT had similar means of bond strength compared to the nonirradiated teeth in enamel, regardless of the adhesive system used. In dentin, CL showed better performance than SB.


Assuntos
Colagem Dentária , Adesivos Dentinários , Resinas Compostas , Cimentos Dentários , Dentina , Humanos , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento , Dente Decíduo
7.
Indian J Dent Res ; 31(3): 470-474, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32769285

RESUMO

Objectives: To evaluate the leachable components of resin cements in oral simulating fluids using high performance liquid chromatography and its resultant shear bond strength with ceramics. Methods: Forty extracted permanent human mandibular molar teeth were sectioned horizontally with a disc beneath the dentino-enamel junction to expose the coronal dentin surface and later finished with 600-grit silicon carbide paper to create a uniform flat surface. Forty Lithium Di-silicate Ceramic block cylinders were sliced in a saw cutting machine at 250 rpm under water-cooling to obtain the discs. The teeth and the ceramic discs were then randomly assigned to two groups on the basis of material used for luting the ceramic disk. Group I: Ceramic disc luted with tooth surface using Variolink II Dual cure Resin Cement, Group II: Ceramic disc luted with tooth surface using multilink speed self-adhesive self-curing resin cement. All ceramic discs were etched with 5% HF acid (IPS Ceramic Etching Gel, Ivoclar, Schaan, Liechtenstein) for 20 seconds, then rinsed thoroughly for 20 seconds and dried for 20 seconds. Ceramic specimens were luted on dentin surfaces with the application of 5 kg load. The samples were stored in 75% ethanol solution for 2 weeks at 37 degree Celsius for chemical aging. HPLC Analysis were performed to analyze the eluted monomer. After HPLC Analysis, Samples were then loaded using universal testing machine for the evaluation of shear bond strength between ceramic discs and the resin cements before and after the elution of monomers. Results: Under HPLC analysis, results showed that the peak release of monomer is Bis-GMA in both the groups. The shear force required to break the bond between the ceramic luted to tooth surface with the resin cements were more for Group I. Statistical results: The statistical analysis was done using ANOVA and paired t-test and it shows P value ≥0.05, hence the null hypothesis is rejected. Conclusion: The monomer eluded from all the groups are identified as Bis-GMA, The eluded monomer decreases the bond strength between the resin cement and the ceramic due to water sorption, The Variolink II (dual cure) resin cement shows improved bond strength than the Multilink (self-cure self-adhesive) resin cement.


Assuntos
Colagem Dentária , Cimentos de Resina , Cerâmica , Cimentos Dentários , Porcelana Dentária , Análise do Estresse Dentário , Humanos , Teste de Materiais , Resistência ao Cisalhamento , Propriedades de Superfície
8.
Dental Press J Orthod ; 25(3): 31-38, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32844970

RESUMO

INTRODUCTION: Orthodontic treatment for adults is currently increasing, and therefore the need to bond brackets to restorations and temporary crowns. The use of CAD/CAM PMMA provisional restorations for orthodontic purposes have not yet been described, and there is currently insufficient information regarding the strength of bracket adhesion. OBJECTIVE: This study aimed at evaluating the effects of thermocycling (TC) and surface treatment on shear bond strength (SBS) of brackets to different provisional materials. METHODS: Forty specimens were made from each material [PMMA (Telio Lab), bis-acryl (Telio CS C&B), and PMMA CAD/CAM (Telio CAD)], sandpapered, and divided according to surface treatment (pumiced or sandblasted) and TC (half of the samples = 1,000 cycles, 5°C/55°C water baths) (n = 10/group). Stainless-steel brackets were bonded to the specimens (using Transbond XT), and SBS testing was performed. Data were analyzed by three-way ANOVA and LSD post-hoc tests (α = 0.05). Failure types were classified with adhesive remnant index (ARI) scores. RESULTS: SBS values ranged from 1.5 to 14.9 MPa. Sandblasted bis-acryl and sandblasted auto-curing PMMA groups presented similar values (p> 0.05), higher than the CAD/CAM material (p< 0.05), with or without TC. When thermocycled, pumiced bis-acryl showed higher SBS than pumiced acrylic (p= 0.005) and CAD/CAM materials (p= 0.000), with statistical difference (p= 0.009). TC showed negative effect (p< 0.05) for sandblasted bis-acryl and pumiced acrylic groups. ARI predominant score was mostly zero (0) for CAD/CAM, 1 and 2 for bis-acryl, and 1 for acrylic groups. CONCLUSION: In general, bis-acryl material showed the highest SBS values, followed by acrylic and CAD/CAM materials, which showed SBS values lower than an optimum strength for bonding brackets.


Assuntos
Colagem Dentária , Braquetes Ortodônticos , Análise do Estresse Dentário , Teste de Materiais , Polimetil Metacrilato , Cimentos de Resina , Resistência ao Cisalhamento , Propriedades de Superfície
9.
Radiol Med ; 125(9): 838-850, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32671554

RESUMO

4D Flow is an emerging MR technique enabling three-dimensional and cardiac phase-resolved flowmetry with ECG-gated phase-contrast MRI that increased the speed of data acquisitions, accuracy and robustness. The method is promoting researches in areas that have not been fully addressed before in the cardiovascular system, such as flowmetry of the bloodstream across the valves, within the heart chambers, complexed flow dynamics such as vortex, helical or retrograde. Wall shear stress and other potential biomarkers derived from 4D Flow are known to be related to vascular wall diseases such as atherosclerosis. In this review, fundamental concepts of 4D Flow technique and post-processing, benefits and limitations as well as its clinical applications are discussed, and the importance of quality control and validation of the method is emphasized. New ideas inspired by 4D Flow can help clinicians and MR scientists further understand the role of flow dynamics in health sciences, diseases and various aspects of cardiovascular physiology.


Assuntos
Circulação Coronária/fisiologia , Imagem Cinética por Ressonância Magnética/métodos , Velocidade do Fluxo Sanguíneo , Eletrocardiografia/métodos , Humanos , Hidrodinâmica , Imageamento Tridimensional/métodos , Angiografia por Ressonância Magnética/métodos , Imagem por Ressonância Magnética/métodos , Fluxo Sanguíneo Regional/fisiologia , Resistência ao Cisalhamento/fisiologia
10.
Eur J Prosthodont Restor Dent ; 28(3): 121-127, 2020 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-32673471

RESUMO

The bonding quality of bonding to polyether ether ketone (PEEK) after different surface treatments and adhesive regimens was assessed through shear bond strength. MATERIALS AND METHODS: Sixty modified PEEK disks were cut out of BioHPP round blanks using CAD-CAM procedures. Disks were subjected to the following surface pretreatments: (A) Sandblasting with alumina (Rocatec) and application of adhesive bonding agent visiolink (control group) (B) Sandblasting with silica-modified alumina (Cojet), application of silane agent Espe Sil, followed by application of adhesive bonding agent Visio-Bond (C) Sandblasting with silica-modified alumina (Cojet), application of silane containing primer-adhesive Clearfil Ceramic Primer, followed by application of adhesive bonding agent visiolink. A dual-curing resin composite cement (combolign) was luted to all treated surfaces. Each group was further divided to subgroups of 10 specimens which were stored in distilled water at 37°C for 150 days without further thermocycling. Specimens were then submitted to shear bond strength testing. RESULTS: Group (B) was statistically significant different from group (A) (control group). Water storage condition had no significant influence on final bond strength. CONCLUSIONS: Use of different conditioning protocols had a significant effect on the final bond strength of composite resin cement to PEEK surface. Water storage did not significantly influence bonding.


Assuntos
Colagem Dentária , Água , Óxido de Alumínio , Resinas Compostas , Éter , Cetonas , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento , Silanos , Propriedades de Superfície
11.
PLoS One ; 15(7): e0235392, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32726315

RESUMO

Platelets upregulate the generation of thrombin and reinforce the fibrin clot which increases the incidence risk of venous thromboembolism (VTE). However, the role of platelets in the pathogenesis of venous cardiovascular diseases remains hard to quantify. An experimentally validated model of thrombin generation dynamics is formulated. The model predicts that a high platelet count increases the peak value of generated thrombin as well as the endogenous thrombin potential (ETP) as reported in experimental data. To investigate the effects of platelets density, shear rate, and wound size on the initiation of blood coagulation, we calibrate a previously developed model of venous thrombus formation and implement it in 3D using a novel cell-centered finite-volume solver. We conduct numerical simulations to reproduce in vitro experiments of blood coagulation in microfluidic capillaries. Then, we derive a reduced one-equation model of thrombin distribution from the previous model under simplifying hypotheses and we use it to determine the conditions of clotting initiation on the platelet count, the shear rate, and the plasma composition. The initiation of clotting also exhibits a threshold response to the size of the wounded region in good agreement with the reported experimental findings.


Assuntos
Coagulação Sanguínea/fisiologia , Plaquetas/fisiologia , Modelos Teóricos , Contagem de Plaquetas/métodos , Testes de Coagulação Sanguínea , Plaquetas/metabolismo , Fibrina/metabolismo , Humanos , Agregação Plaquetária/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Resistência ao Cisalhamento/fisiologia , Trombina/metabolismo , Tromboplastina/metabolismo , Trombose/metabolismo , Trombose/fisiopatologia , Veias/metabolismo , Veias/fisiologia
12.
J Adhes Dent ; 22(4): 421-431, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32666069

RESUMO

PURPOSE: To investigate the effects of 1-year water storage and surface treatments on shear bond strength (SBS) of two composite cements bonded to resin matrix CAD-CAM ceramics (RMCs) and on the mechanical properties of RMCs. MATERIALS AND METHODS: Three types of RMCs were tested: 1. polymer-infiltrated hybrid ceramic (PIHC, Enamic, VITA Zahnfabrik); 2. resin nanoceramic (RNC, Lava Ultimate, 3M Oral Care); and 3. flexible hybrid ceramic (FHC, Cerasmart, GC). One indirect laboratory composite (ILC, Epricord, Kuraray Noritake) was used as control. For each material, 60 plates (14 x 7 x 1 mm) were prepared for the SBS test and submitted to three different surface treatments: following manufacturer's instructions, non-thermal atmospheric plasma application (30 s), and plasma + bonding agent. Two composite cements were tested: RelyX Ultimate (3M Oral Care) and Panavia V5 (Kurarary Noritake). Two resin cylinders (1.5 mm diameter x 1.5 mm height) were bonded to each plate (n = 10), with one tested after 24-h storage in distilled water and the other after 1 year of storage in distilled water. Twenty rectangular bars (12 x 2 x 1 mm) of each indirect material were prepared and submitted to the 3-point flexural test after 24-h or 1-year water storage to determine the elastic modulus (EM) and flexural strength (FS) (n = 10). Fractured samples were also examined with SEM and energy dispersive x-ray spectroscopy (EDS). SBS data were analyzed by four-way ANOVA, and EM and FS data by two-way ANOVA, followed by Tukey's post-hoc test (α = 0.05). RESULTS: Groups treated in accordance with manufacturer's instructions exhibited higher SBS than did plasma and plasma + bonding agent groups for all indirect materials, composite cements, and storage periods tested. In general, RelyX Ultimate displayed higher mean SBS than did Panavia V5, except for some groups of ILC where manufacturer's instructions were followed. After 1-year storage in water, all groups exhibited a significant reduction in SBS, except for some groups that following manufacturer's instructions. ILC showed the lowest values of EM and FS. Among the CAD-CAM materials, FHC exhibited the lowest EM and highest FS means, while PIHC possessed the highest EM and lowest FS means for both storage periods. CONCLUSIONS: In general, following the respective manufacturer's instructions yielded the best bond strength results. For most materials, 1-year water storage decreased bond strength of composite cements to RMCs, as well as their FS, while increasing their EM. Microstructure and composition influenced the mechanical properties studied.


Assuntos
Cerâmica , Colagem Dentária , Desenho Assistido por Computador , Teste de Materiais , Polímeros , Cimentos de Resina , Resistência ao Cisalhamento , Propriedades de Superfície
13.
PLoS One ; 15(7): e0236371, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32706802

RESUMO

We present a simple but accurate algorithm to calculate the flow and shear rate profile of shear thinning fluids, as typically used in biofabrication applications, with an arbitrary viscosity-shear rate relationship in a cylindrical nozzle. By interpolating the viscosity with a set of power-law functions, we obtain a mathematically exact piecewise solution to the incompressible Navier-Stokes equation. The algorithm is validated with known solutions for a simplified Carreau-Yasuda fluid, full numerical simulations for a realistic chitosan hydrogel as well as experimental velocity profiles of alginate and chitosan solutions in a microfluidic channel. We implement the algorithm in an easy-to-use Python tool, included as Supplementary Material, to calculate the velocity and shear rate profile during the printing process, depending on the shear thinning behavior of the bioink and printing parameters such as pressure and nozzle size. We confirm that the shear stress varies in an exactly linear fashion, starting from zero at the nozzle center to the maximum shear stress at the wall, independent of the shear thinning properties of the bioink. Finally, we demonstrate how our method can be inverted to obtain rheological bioink parameters in-situ directly before or even during printing from experimentally measured flow rate versus pressure data.


Assuntos
Alginatos/química , Quitosana/química , Hidrogéis/química , Agulhas , Impressão Tridimensional/instrumentação , Algoritmos , Hidrodinâmica , Microfluídica , Resistência ao Cisalhamento , Viscosidade
14.
Stomatologiia (Mosk) ; 99(3): 7-10, 2020.
Artigo em Russo | MEDLINE | ID: mdl-32608941

RESUMO

OBJECTIVE: To study the dynamics of changes in the adhesion between the composite and dentin of the tooth when using different volumes of a single-component adhesive system in case of contamination of it with human blood plasma. MATERIAL AND METHODS: To achieve this goal, the following were used: extracted human teeth, XP Bond one-component adhesive systems (DENTSPLY, Germany), Esthet X HD micrometric restoration material (DENTSPLY, Germany), and centrifuged blood plasma. The strength of the adhesive bond between the composite material and the hard tissues of the tooth was studied using a shear test machine Zwick Roell Z 010 («Zwick¼, Germany). RESULTS: The use of a single-component adhesive system in an amount of 17.7 mg (1 drop from a dispenser) for treating open dentin makes it more resistant to contamination compared to using the same adhesive, but in an amount of 6.6 mg (the amount of adhesive that adsorbs a medium-sized dental take). A decrease in the adhesion force between the composite material and tooth hard tissues from 1.5 to 17.7% occurs when a single-component adhesive system weighing 17.7 mg of blood plasma simulating a dentinal fluid weighing from 0.2 to 2.0 mg enters. The ingestion of the same amount of blood plasma in a single-component adhesive system weighing 6.6 mg leads to a decrease in its adhesion from 4.3 to 43%.


Assuntos
Colagem Dentária , Resinas Compostas , Cimentos Dentários , Análise do Estresse Dentário , Dentina , Humanos , Teste de Materiais , Cimentos de Resina , Resistência ao Cisalhamento
15.
Environ Sci Pollut Res Int ; 27(27): 33848-33862, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32533492

RESUMO

The leachate (pH = 14) from alumina production changes the mechanical properties of red clay, and the shear strength parameters of the system vary due to the multiple-dimensional interactions of the microscopic parameters. In this paper, the alumina production liquid and the concentrations of the NaOH solution were designed to contaminate the red clay during 80 days. The cohesion and friction angle of the alkaline-contaminated red clay were obtained from direct shear tests. Through qualitative and quantitative analyses using scanning electron microscopy (SEM), the microstructure was observed. Based on the rock engineering systems (RES) theory, interactions among microscopic parameters were analysed, and the relationships between shear strength parameters and microscopic parameters of alkaline-contaminated red clay were established. Results show that both of the cohesion and friction angle of alkaline-contaminated red clay are increased in general; the adsorption in alumina production liquid and dispersing effect of 0.7% NaOH concentration are noticeable, and the interactions of the microscopic parameters are intense; the ratio of the intra-aggregate pore number, the probability distribution index and the number of particles can significantly influence cohesion; the particle morphology fractal dimension, aspect and probability entropy have a severe effect on friction angle. This work is expected to serve as a reference for future research on the relationship between macroscopic properties and microcosmic structure of soil.


Assuntos
Argila , Poluentes do Solo , Adsorção , Resistência ao Cisalhamento , Solo
16.
Pediatr Dent ; 42(3): 221-225, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32522327

RESUMO

Purpose: The purpose of this study was to measure the shear bond strength (SBS) of glass ionomer cement (GIC) to artificial carious dentin with and without silver diamine fluoride (SDF) treatment. Methods: Permanent molars were sectioned and demineralized to create artificial carious lesions. In five groups, the demineralization of dentin, application of SDF, use of conditioner, and elapsed time between the placement of SDF and restoration were tested for differences in SBS using an UltraTester machine. Statistical analysis was done using the Kruskal-Wallis test and Tukey-Kramer multiple comparison tests. Results: The highest bond strength was found when GIC was placed on conditioned and demineralized dentin treated with SDF one week earlier. Treatment with SDF and use of conditioner did not statistically affect the SBS of GIC to demineralized dentin. Statistically significant increases in bond strength were found when one week elapsed between SDF application and GIC placement. The lowest bond strength was found with immediate GIC application onto SDF-treated demineralized dentin. Conclusions: These in vitro findings suggest that silver diamine fluoride treatment does not significantly affect the bond strength of glass ionomer cement to dentin lesions, and improved retention is obtained by allowing SDF solution to set for one week prior to GIC placement.


Assuntos
Colagem Dentária , Cárie Dentária , Dentina , Fluoretos Tópicos , Cimentos de Ionômeros de Vidro , Humanos , Teste de Materiais , Compostos de Amônio Quaternário , Resistência ao Cisalhamento , Compostos de Prata
17.
J Orofac Orthop ; 81(5): 350-359, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32500218

RESUMO

OBJECTIVE: The goal was to evaluate the adhesive shear bond strength (SBS) of orthodontic tubes bonded to molar teeth and reinforced with Transbond XT (3M Science, St. Paul, MN, USA) and flowable resin. MATERIALS AND METHODS: In all, 120 molar teeth, previously extracted from patients with a mean age of 30 were included. Orthodontic molar tubes were bonded on the vestibular surface of these teeth with one of two types of adhesive (Transbond XT [3M Science, St. Paul, MN, USA] or Orthobond [Morelli, Sorocaba, Brazil]). Each of these groups was subsequently divided into four further groups: control and those subjected to the use of resin reinforcement on the occlusal surface of the bonded tubes with one of three materials (Transbond XT, Tetric N Flow [Ivoclar Vivadent, Ellwangen, Germany], Z 350 Flow [3M Science, St. Paul, MN, USA]). SBS and adhesive remnant index tests were performed to evaluate bond strength and type of fracture of the tubes bonded with the different methods. RESULTS: The use of resin reinforcement with Transbond XT significantly increased the SBS of tubes bonded with both materials. Flowable composites did not increase the SBS when used as a reinforcement. Less than 50% of the adhesive remained on the vestibular surface after the SBS test in most samples of all groups. CONCLUSION: Transbond XT orthodontic adhesive and Orthobond adhesive had appropriate bonding strengths for clinical use. Furthermore, the use of a resinous reinforcement with Transbond XT significantly increased the SBS of tubes bonded. However this technique with flowable adhesives (Tetric N Flow and Z350 Flow) did not significantly increase SBS when orthodontic tubes were bonded with Transbond XT or Orthobond.


Assuntos
Colagem Dentária , Braquetes Ortodônticos , Análise do Estresse Dentário , Alemanha , Humanos , Teste de Materiais , Dente Molar , Cimentos de Resina , Resistência ao Cisalhamento
18.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 38(3): 256-262, 2020 Jun 01.
Artigo em Chinês | MEDLINE | ID: mdl-32573131

RESUMO

OBJECTIVE: This study aimed to develop novel self-adhesive resin cement with antibacterial and self-healing properties. Furthermore, the dentin bonding strength, mechanical properties, self-healing efficiency, and antibacterial property of the developed cement were measured. METHODS: Novel nano-antibacterial inorganic fillers that contain quaternary ammonium salts with long-chain alkyls were synthesized. These fillers were added into self-adhesive resin cement containing self-healing microcapsules at mass fractions of 0, 2.5%, 5.0%, 7.5%, or 10.0%. The dentin shear bonding test was used to test the bonding strength, whereas the flexural test was used to measure the flexural strength and elastic modulus of the cement. The single-edge V-notched beam method was used to measure self-healing efficiency, and human dental plaque microcosm biofilms were chosen to calculate the antibacterial property. RESULTS: The dentin shear bond strength significantly decreased when the mass fraction of the nano-antibacterial inorganic fillers in the novel cement reached 7.5% (P<0.05). The incorporation of 0, 2.5%, 5.0%, 7.5%, or 10.0% mass fraction of nano-antibacterial inorganic fillers did not adversely affect the flexural strength, elastic modulus, fracture toughness, and self-healing efficiency of the cement (P>0.1). Resin cement containing 2.5% mass fraction or more nano-antibacterial inorganic fillers significantly inhibited the metabolic activity of dental plaque microcosm biofilms, indicating strong antibacterial potency (P<0.05). CONCLUSIONS: The novel self-adhesive resin cement exhibited promising antibacterial and self-healing properties, which enable the cement to be used for dental applications.


Assuntos
Colagem Dentária , Cimentos de Resina , Antibacterianos , Cimentos Dentários , Análise do Estresse Dentário , Dentina , Humanos , Teste de Materiais , Resistência ao Cisalhamento , Propriedades de Superfície
19.
J Vis Exp ; (159)2020 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-32478730

RESUMO

The properties of cured wood adhesives are difficult to study because of the loss of water and other components to the wood, the influence of wood on the adhesive cure, and the effect of adhesive penetration on the wood interphase; thus, normal testing of a neat adhesive film is generally not useful. Most tests of wood adhesive bond strength are slow, laborious, can be strongly influenced by the wood and do not provide information on the kinetics of cure. Test method ASTM D 7998-19, however, can be used for fast evaluation of the strength of wood bonds. The use of a smooth, uniform, and strong wood surface, like maple face-veneer, and sufficient bonding pressure reduces the adhesion and wood strength effects on bond strength. This method has three main applications. The first is to provide consistent data on bond strength development. The second is to measure the dry and wet strengths of bonded lap shear samples. The third is to better understand the adhesive heat resistance by quickly evaluating thermal sensitivity and distinguishing between thermal softening and thermal degradation.


Assuntos
Adesivos/química , Teste de Materiais/métodos , Madeira/química , Resistência ao Cisalhamento
20.
Niger J Clin Pract ; 23(6): 792-797, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32525113

RESUMO

Background: There is no information about the shear bond strengths (SBS) of zirconia ceramic to primary tooth dentin. Aim: To investigate the effect of different surface treatments and cements on the shear bond strength (SBS) of zirconia ceramic to primary tooth dentin. Materials and Methods: Prepared zirconia bars were distributed into four groups according to surface treatment procedure: control, sandblasting, CoJet and hot etching. The zirconia specimens in each group were further divided into subgroups according to cement (n = 13): self-adhesive resin (Rely-X Unicem), resin-modified glass ionomer (Ketac-Cem Plus), and universal bioactive (BioCem). Zirconia specimens were bonded to the primary tooth dentin surface by cement. SBS was measured, and the data were subjected to two-way ANOVA and Tukey's tests. Results: Statistical differences were observed in the surface treatment procedures for Rely-X Unicem (P < 0.05), but no statistically significant differences were found in the sandblasting, CoJet and hot-etching groups for Ketac-Cem Plus (P > 0.05). For BioCem, the SBS value for the hot etching group was significantly lower than those for the CoJet and sandblasting groups (P < 0.05). The SBS values for the Rely-X Unicem subgroups (sandblasting, CoJet and hot etching) were significantly higher than those for the other cements (P < 0.05). Conclusion: The bond strength of zirconia ceramic to primary tooth dentin is affected by surface treatments and cements.


Assuntos
Cerâmica/química , Colagem Dentária , Dentina , Cimentos de Resina/química , Resistência ao Cisalhamento , Dente Decíduo , Zircônio/química , Resinas Acrílicas , Adesivos , Cimentos de Ionômeros de Vidro , Humanos , Teste de Materiais , Dióxido de Silício , Propriedades de Superfície
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