Dynamic Viscoelastic Characterization of Bulk-fill Resin-based Composites and Their Conventional Counterparts

2020 ◽  
Vol 45 (2) ◽  
pp. 173-182 ◽  
Author(s):  
AU Yap ◽  
AH Eweis ◽  
NA Yahya
Keyword(s):  
Aqueous Solutions ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Water Solution ◽  
Artificial Saliva ◽  
High Stress ◽  
Mechanical Analysis ◽  
Significance Level ◽  
Post Hoc ◽  
The Impact

SUMMARY This study compared the viscoelastic properties of restorative and flowable bulk-fill resin-based composites (RBCs) with their conventional counterparts and evaluated the impact of aqueous solutions on viscoelastic properties. The materials examined included three conventional RBCs (Filtek Z350, Tetric N Ceram, and Beautifil II), three restorative bulk-fill RBCs (Filtek Bulk-Fill Restorative, Tetric N Ceram Bulk-Fill, and Beautifil Bulk-Fill Restorative) in addition to three flowable bulk-fill RBCs (Filtek Bulk-Fill Flowable, Tetric N Flow Bulk-Fill, and Beautifil Bulk-Fill Flowable). Beam-shaped specimens (12×2×2 mm) were fabricated using customized stainless-steel molds, finished, and measured. The specimens were randomly divided into four groups and conditioned in air (control), artificial saliva, 0.02 N citric acid, and 50% ethanol-water solution for seven days at 37°C. They were then subjected to dynamic mechanical analysis (n = 10) in flexure mode at 37°C with a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to statistical analysis using one-way analysis of variance/Tukey post hoc test at a significance level of α = 0.05. Viscoelastic properties of the RBCs were found to be product and conditioning medium dependent. For most RBCs, exposure to aqueous solutions, particularly an ethanol-water solution, degraded viscoelastic properties. With the exception of Filtek Bulk-Fill Restorative, bulk-fill restorative and flowable RBCs generally had significantly lower storage and loss modulus than their conventional counterparts regardless of conditioning medium. Conventional RBCs are thus favored over their bulk-fill counterparts, particularly for high-stress-bearing areas.

scholarly journals Viscoelastic Properties of Contemporary Bulk-fill Restoratives: A Dynamic-mechanical Analysis

2018 ◽  
Vol 43 (3) ◽  
pp. 307-314 ◽  
Author(s):  
JEX Ong ◽  
AU Yap ◽  
JY Hong ◽  
AH Eweis ◽  
NA Yahya
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Storage Modulus ◽  
Loss Tangent ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Artificial Saliva ◽  
Mechanical Analysis ◽  
Distilled Water ◽  
Glass Ionomer ◽  
Dynamic Mechanical

SUMMARY This study investigated the viscoelastic properties of contemporary bulk-fill restoratives in distilled water and artificial saliva using dynamic mechanical analysis. The materials evaluated included a conventional composite (Filtek Z350), two bulk-fill composites (Filtek Bulk-fill and Tetric N Ceram), a bulk-fill giomer (Beautifil-Bulk Restorative), and two novel reinforced glass ionomer cements (Zirconomer [ZR] and Equia Forte [EQ]). The glass ionomer materials were also assessed with and without resin coating (Equia Forte Coat). Test specimens 12 × 2 × 2 mm of the various materials were fabricated using customized stainless-steel molds. After light polymerization/initial set, the specimens were removed from the molds, finished, measured, and conditioned in distilled water or artificial saliva at 37°C for seven days. The materials (n=10) were then subjected to dynamic mechanical testing in flexure mode at 37°C and a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to normality testing and statistical analysis using one-way analysis of variance/Dunnett's test and t-test at a significance level of p < 0.05. Mean storage modulus ranged from 3.16 ± 0.25 to 8.98 ± 0.44 GPa, while mean loss modulus ranged from 0.24 ± 0.03 to 0.65 ± 0.12 GPa for distilled water and artificial saliva. Values for loss tangent ranged from 45.7 ± 7.33 to 134.2 ± 12.36 (10−3). Significant differences in storage/loss modulus and loss tangent were observed between the various bulk-fill restoratives and two conditioning mediums. Storage modulus was significantly improved when EQ and ZR was not coated with resin.

Impact of Different Fiber Reinforcement on Flexural Strength, Fracture Toughness and Abrasive Resistance of Provisional Restorative Resin

2021 ◽  
Author(s):  
Dr. Pratik Bhatnagar
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Flexural Strength ◽  
Clinical Performance ◽  
Testing Machine ◽  
Surface Hardness ◽  
Abrasive Resistance ◽  
Significance Level ◽  
Post Hoc ◽  
The Impact

Aim: To assess and compare the impact of reinforcement of PMMA with glass fibre, polyethylene fibre and carbon fibres on flexural strength, fracture toughness and abrasive resistance. Background: In view of inadequate mechanical and physical characteristics of PMMA which include low impact strength and low surface hardness and resulting lowered clinical performance of the prosthesis, the study was designed to investigate the impact of reinforcement of PMMA with glass, polyethylene and carbon fibers on flexural strength, fracture toughness and abrasive resistance. Methods and Findings: Rectangular specimens (n=120; 30 each from 4 groups; 65 × 10 × 3.3 mm3) were fabricated and loaded on Universal Testing Machine until fracture for flexural strength and fracture toughness and on Taber Abrasive Tester for abrasive resistance. Data were analyzed using one–way ANOVA followed by Post Hoc test - Bonferroni multiple comparison analysis, using significance level of 0.05. Significant increase in fracture toughness was observed in specimens reinforced with polyethylene and carbon fiber, albeit the values of flexural strength were increased insignificantly. Specimens reinforced with glass and carbon fiber had significantly low values of abrasive resistance. Conclusion: Findings indicate that reinforcement of PMMA by non-specific fibers like glass, polyethylene and carbon resulted in significant increase in fracture toughness and decrease in abrasive resistance.

Mechanical and thermal properties of polybutylene terephthalate/ethylene-vinyl acetate blends using vane extruder

e-Polymers ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Cong Meng ◽  
Jin-ping Qu
Keyword(s):  
Impact Strength ◽  
Vinyl Acetate ◽  
Loss Modulus ◽  
Weight Fraction ◽  
Ethylene Vinyl Acetate ◽  
Mechanical Analysis ◽  
Mechanical And Thermal Properties ◽  
Polybutylene Terephthalate ◽  
Scanning Calorimetry ◽  
The Impact

AbstractThe poly(butylene terephthalate) (PBT)/ethylene-vinyl acetate copolymer (EVA) blends with different contents of EVA were prepared by an vane extruder. From the observation of morphologies, impact strength and dynamic mechanical analysis (DMA), the EVA particles were well dispersed in the PBT matrix and improved the impact strength of PBT. Differential scanning calorimetry measurements demonstrate that there is little diversification in the crystal structure and type. Thermogravimetric analysis reveals that as the weight fraction of EVA increases, the thermal stability of composite is enhanced. The rheological analyses indicate that the PBT/EVA blends follow a non-Newtonian behavior and viscosities of the blends are drastically lower than that of pure PBT at higher frequencies. The storage modulus (G′) and loss modulus (G″) of the blends monotonously increase as the frequency rises. This work provides a novel method to develop blends with excellent performance.

Comparison of Flexural Properties of Bulk-fill Restorative/Flowable Composites and Their Conventional Counterparts

2020 ◽  
Vol 45 (1) ◽  
pp. 41-51 ◽  
Author(s):  
AH Eweis ◽  
AU Yap ◽  
NA Yahya
Keyword(s):  
Water Solution ◽  
Artificial Saliva ◽  
Flexural Modulus ◽  
Testing Machine ◽  
Flexural Properties ◽  
Significance Level ◽  
Tukey Test ◽  
Universal Testing ◽  
Flexural Testing ◽  
Flowable Composites

SUMMARY The objectives of the study were to compare the flexural modulus and strength of restorative and flowable bulk-fill resin-based composites (RBCs) to their conventional counterparts and to determine the effects of conditioning environment on their flexural properties. The materials evaluated included three conventional RBCs (Filtek Z350, Tetric N Ceram, and Beautifil II), three restorative bulk-fill RBCs (Filtek Bulk-Fill Restorative, Tetric N Ceram Bulk-Fill, and Beautifil Bulk-fill Restorative), as well as three flowable bulk-fill RBCs (Filtek Bulk-Fill Flowable, Tetric N Flow Bulk-Fill, and Beautifil Bulk-Fill Flowable). Specimens were fabricated using customized stainless-steel molds, finished, measured, and randomly divided into four groups. The various RBCs were conditioned in the following mediums (n=10) for seven days at 37°C: air, artificial saliva (SAGF), 0.02 N citric acid, and 50% ethanol-water solution. After conditioning, the specimens were rinsed, blotted dry, measured, and subjected to flexural testing using a universal testing machine. Data were subjected to statistical analysis using analysis of variance and the Tukey test at a significance level of α = 0.05. Significant differences in flexural properties were observed between materials and conditioning mediums. Bulk-fill restorative RBCs exhibited higher flexural modulus than their bulk-fill flowable and conventional counterparts. With the exception of Filtek Bulk-Fill Flowable, bulk-fill flowable RBCs had significantly higher flexural strength than bulk-fill restorative and conventional RBCs. Flexural properties were highest when RBCs were conditioned in air and generally the lowest after exposure to ethanol.

Preparation and Viscoelastic Properties of Waterborne Polyurethane/Cellulose Nanocrystals Composites

2013 ◽  
Vol 771 ◽  
pp. 105-108 ◽  
Author(s):  
Qun Zhao ◽  
Ke Lu Yan
Keyword(s):  
Cellulose Nanocrystals ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Casting Process ◽  
Waterborne Polyurethane ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Ultrasonic Dispersion ◽  
Mechanical Reinforcement ◽  
Power Law Equation

The objective of this work is to study the viscoelastic properties by which nanofillers produce mechanical reinforcement in polymers using dynamic mechanical analysis (DMA). To this purpose, waterborne polyurethane (WBPU) and cellulose nanocrystals (CNCs) composites films with various filler contents were prepared by ultrasonic dispersion followed by emulsion casting process. In frequency sweep tests, the storage modulus and loss modulus were recorded and modeled by the Power Law equation. CNCs precipitation significantly increased the steady state viscous properties of cellulose nanocoposite films but decreased the dynamic viscoelastic properties and frequency sensitivity of nanocomposite films.

scholarly journals Mechanical testing of glutaraldehyde cross-linked mitral valves. Part two: Elastic and viscoelastic properties of chordae tendineae

2020 ◽  
pp. 095441192097593
Author(s):  
Matthew Constable ◽  
Rhiannon Northeast ◽  
Bernard M Lawless ◽  
Hanna E Burton ◽  
Vera Gramigna ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Cross Linking ◽  
Chordae Tendineae ◽  
Mitral Valves ◽  
Lower Strain ◽  
The Mean

The aim of this study was to assess whether the mechanical properties of mitral valve chordae tendineae are sensitive to being cross-linked under load. A total 64 chordae were extracted from eight porcine hearts. Two chordae (posterior basal) from each heart were subjected to uniaxial ramp testing and six chordae (two strut, two anterior basal and two posterior basal) were subjected to dynamic mechanical analysis over frequencies between 0.5 and 10 Hz. Chordae were either cross-linked in tension or cross-linked in the absence of loading. Chordae cross-linked under load transitioned from high to low extension at a lower strain than cross-linked unloaded chordae (0.07 cf. 0.22), with greater pre-transitional (30.8 MPa cf. 5.78 MPa) and post-transitional (139 MPa cf. 74.1 MPa) moduli. The mean storage modulus of anterior strut chordae ranged from 48 to 54 MPa for cross-linked unloaded chordae, as compared to 53–61 MPa cross-linked loaded chordae. The mean loss modulus of anterior strut chordae ranged from 2.3 to 2.9 MPa for cross-linked unloaded chordae, as compared to 3.8–4.8 MPa cross-linked loaded chordae. The elastic and viscoelastic properties of chordae following glutaraldehyde cross-linking are dependent on the inclusion/exclusion of loading during the cross-linking process; with loading increasing the magnitude of the material properties measured.

scholarly journals Effect of COVID-19 Pandemic on the Levels of Empathy among Undergraduate Dental Students in Pakistan

2020 ◽  
Vol 14 (S 01) ◽  
pp. S110-S115
Author(s):  
Sundas Ghaus ◽  
Madiha Abdul Waheed ◽  
Shahreen Zahid Khan ◽  
Laila Mustafa ◽  
Sohaib Siddique ◽  
...  
Keyword(s):  
Dental Students ◽  
Cross Sectional Survey ◽  
Chi Square ◽  
Cross Sectional ◽  
Significance Level ◽  
Significant Difference ◽  
Chi Square Test ◽  
Post Hoc ◽  
The Impact ◽  
One Way Anova

Abstract Objective The purpose of our study is to determine the effect of coronavirus disease 2019 (COVID-19) on the levels of empathy toward patients among undergraduate dental students in Pakistan. Materials and Methods A cross-sectional, survey-based study was conducted at Islamic International Dental College, Islamabad, Pakistan. After taking an informed consent, a validated and pretested Toronto Empathy Questionnaire (TEQ) was distributed amongst the undergraduate dental students at two points, one before the COVID-19 existed, and the other after August 7th, 2020, when the COVID-19 cases dropped in Pakistan. Responses were indicated on a five point Likert Scale. Statistical Analysis A one-way ANOVA (analysis of variance) was used to compare the TEQ scores between the different years of education at the dental school. Difference within the groups was analyzed using the post-hoc Tukey test. Pre- and post-COVID-19 comparison was done using the Chi-square test (significance level p < 0.05). Results A total of 221 out of 260 students in the pre-COVID-19 group, while 210 out of 260 students in the post-COVID-19 group enrolled in the dentistry program participated in the study. Significant difference in the empathy levels was observed in the pre- and post-COVID-19 groups of the same population, i.e., (p < 0.05). The response rate was 85%. Conclusions This study showed an increase in mean empathy scores among the undergraduate dental students after COVID-19, indicating a significant improvement in their empathy levels during the time of COVID-19. It highlights the impact of the pandemic, whereby death and chaos seem to have brought about an improvement in interpersonal harmony.

scholarly journals HUBUNGAN STRES KERJA DENGAN PRODUKTIVITAS KERJA PERAWAT DI RSU GMIM BETHESDA TOMOHON

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Astari Bella Andini ◽  
B H Ralph Kairupan ◽  
Lenny Gannika
Keyword(s):  
Work Stress ◽  
High Stress ◽  
Work Productivity ◽  
P Value ◽  
Chi Square ◽  
Cross Sectional ◽  
Significance Level ◽  
Chi Square Test ◽  
Patient Responses ◽  
The Impact

Absract : Stress is an epidemic that spreads throughout around the world. The job of a nurse is a job that has a high stress, because in working nurses relate directly to patients with different disease diagnoses and patient responses. the impact of stress of work can have an impact on the productivity of the work of nurses. The purpose of the study was to determine the relationship between stress of work with Work Productivity of nurse at RSU GMIM Bethesda Tomohon. Method in this research uses descriptive analytic research design with cross sectional approach. The sample in this study was nurses in the room of residence care of the RSU GMIM Bethesda Tomohon, with a population is 61 nurses. Results of the study used the chi square test at a significance level of 95%, significant for stress of work with Work Productivity of nurse ( p value 0,0013 ; α 0,05). Conclusion, work stress is significantly related with Nurse Work Productivity at RSU GMIM Bethesda TomohonKeywords : Work Stress, Work ProductivityAbstrak : Stres merupakan epidemi yang menyebar ke seluruh dunia. Pekerjaan seorang perawat merupakan pekerjaan yang memiliki stres yang tinggi karena dalam bekerja perawat berhubungan langsung dengan berbagai macam pasien dengan diagnosa penyakit dan respon yang berbeda-beda. Dampak dari stres kerja tersebut dapat berdampak pada produktivitas kerja perawat. Tujuan penelitian Untuk diketahui adanya Hubungan stres kerja dengan produktivitas kerja perawat di RSU GMIM Bethesda Tomohon. Metode penelitian ini menggunakan desain penelitian dekriptif analitik korelasi dengan pendekatan cross sectional. Sampel penelitian ini adalah perawat di ruang rawat inap RSU GMIM Bethesda Tomohon, dengan jumlah populasi adalah 61 perawat.. Hasil penelitian dengan menggunakan uji chi square pada tingkat kemaknaan 95%, signifikan untuk stres kerja dengan produktivitas kerja perawat (nilai p 0,0013 ; α 0,05).Kata Kunci : Stres Kerja, Produktivitas Kerja.

scholarly journals Effect of Dietary Challenges on the Flexural Properties of Resin-based Composites

2021 ◽  
Vol 28 ◽  
pp. 52-60
Author(s):  
Noor Azlin Yahya ◽  
Shi Yin Lim ◽  
Maria Angela Garcia Gonzalez
Keyword(s):  
Flexural Strength ◽  
Material Selection ◽  
Water Solution ◽  
Artificial Saliva ◽  
Flexural Modulus ◽  
Dietary Advice ◽  
Flexural Properties ◽  
Air Exposure ◽  
Flexural Testing ◽  
The Impact

This study aims to compare flexural strength and flexural modulus of different resin-based composites (RBCs) and to determine the impact of dietary solvents on flexural properties. Forty specimens (12x2x2mm) for each of two conventional (Aura Easy [AE]; Harmonize [HN]) and one bulk fill (Sonic Fill 2 [SF2]) were fabricated using customised plastic moulds. Specimens were light-cured, measured and randomly divided into four groups. The groups (n=10) were conditioned for 7 days at 37°C: in one of media: air (control), artificial saliva (SAGF), 0.02N citric acid and 50% ethanol–water solution. After conditioning, the specimens subjected to flexural testing. Two-way ANOVA and one-way ANOVA (post hoc: Tukey’s or Dunnett T3 tests) were used at a=0.05. Significant differences in flexural properties were observed between materials and conditioning media. Flexural strength and modulus values ranged from 124.85MPa to 51.25MPa; and 6.76GPa to 4.03GPa, respectively. The highest flexural properties were obtained with conditioning in air. Exposure to aqueous solutions generally reduced flexural properties. In conclusion, the effect of dietary solvents on flexural properties were material and medium dependent. For functional longevity of restorations, patients’ alcohol intake should be considered during material selection. Dietary advice (reduce alcohol consumption) should be given to patients post operatively.

scholarly journals The Dynamic Viscoelasticity of Dental Soft Polymer Material Containing Citrate Ester-Based Plasticizers

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5078
Author(s):  
Guang Hong ◽  
Wei-qi Wang ◽  
Lu Sun ◽  
Jian-min Han ◽  
Keiichi Sasaki
Keyword(s):  
Polymer Material ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Polymer Materials ◽  
Significance Level ◽  
Dynamic Viscoelasticity ◽  
Methacrylate Polymers ◽  
Significant Difference ◽  
Tan Δ ◽  
Soft Polymer

The aim of this study was to investigate the dynamic viscoelasticity of dental soft polymer material containing citrate ester-based plasticizers. Three kinds of citrate ester-based plasticizer (Citroflex® C-2: TEC, Citroflex® A-2: ATEC, and Citroflex® A-4: ATBC), with the combination of 5 wt% ethyl alcohol, were used as the liquid phase. The dynamic viscoelastic properties of nine ethyl methacrylate polymers: (A, B, C, D, E, F, G, H, and I) were immersed in 37 °C distilled water for 0, 1, 3, 7, 14 and 30 days, respectively. The dynamic viscoelastic properties were measured at 37 °C with an automatic dynamic mechanical analyzer. The shear storage modulus (G′), shear loss modulus (G″), and loss tangent (tan δ) were determined at 1 Hz. These parameters were statistically analyzed by two-way and one-way ANOVA and Tukey’s multiple comparison test at a predetermined significance level of 0.05. A significant difference was found among the materials in terms of the dynamic viscoelasticity. The materials containing citrate ester-based plasticizer ATBC showed the most stable dynamic viscoelasticity. Considering the limitations of this study, the results suggest that the inclusion of citrate ester-based plasticizer can improve the durability of dental soft polymer materials.

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