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5541 KiB

Open AccessArticle

Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys

by Mi-Kyung Han, Jai-Youl Kim, Moon-Jin Hwang, Ho-Jun Song and Yeong-Joon Park

Materials 2015, 8(9), 5986-6003; https://doi.org/10.3390/ma8095287 - 9 Sep 2015

Cited by 105 | Viewed by 7952

Abstract

In this paper, the effects of Nb addition (5–20 wt %) on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed [...] Read more.

In this paper, the effects of Nb addition (5–20 wt %) on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed using X-ray diffraction (XRD), SEM, and TEM. The results indicated that the Ti-xNb alloys (x = 10, 15, and 20 wt %) were mainly composed of α + β phases with precipitation of the isothermal ω phase. The volume percentage of the ω phase increased with increasing Nb content. We also investigated the effects of the alloying element Nb on the mechanical properties (including Vickers hardness and elastic modulus), oxidation protection ability, and corrosion behavior of Ti-xNb binary alloys. The mechanical properties and corrosion behavior of Ti-xNb alloys were found to be sensitive to Nb content. These experimental results indicated that the addition of Nb contributed to the hardening of cp-Ti and to the improvement of its oxidation resistance. Electrochemical experiments showed that the Ti-xNb alloys exhibited superior corrosion resistance to that of cp-Ti. The cytotoxicities of the Ti-xNb alloys were similar to that of pure titanium. Full article

(This article belongs to the Special Issue Dental Materials)

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710 KiB

Open AccessArticle

Physical Properties of an Ag-Doped Bioactive Flowable Composite Resin

by Hiba Kattan, Xanthippi Chatzistavrou, James Boynton, Joseph Dennison, Peter Yaman and Petros Papagerakis

Materials 2015, 8(8), 4668-4678; https://doi.org/10.3390/ma8084668 - 24 Jul 2015

Cited by 17 | Viewed by 4880

Abstract

The aim of this work was to study the physical and antibacterial properties of a flowable resin composite incorporating a sol-gel derived silver doped bioactive glass (Ag-BGCOMP). The depth of the cure was calculated by measuring the surface micro-hardness for the top and [...] Read more.

The aim of this work was to study the physical and antibacterial properties of a flowable resin composite incorporating a sol-gel derived silver doped bioactive glass (Ag-BGCOMP). The depth of the cure was calculated by measuring the surface micro-hardness for the top and bottom surfaces. The volumetric polymerization shrinkage was measured by recording the linear shrinkage as change in length, while the biaxial flexural strength was studied measuring the load at failure. The antibacterial properties of the samples were tested against Streptococcus mutans (S. mutans) and Lactobacillus casei (L. casei). The measured values were slightly decreased for all tested physical properties compared to those of control group (flowable resin composite without Ag-BG), however enhanced bacteria inhibition was observed for Ag-BGCOMP. Ag-BGCOMP could find an application in low stress-bearing areas as well as in small cavity preparations to decrease secondary caries. This work provides a good foundation for future studies on evaluating the effects of Ag-BG addition into packable composites for applications in larger cavity preparations where enhanced mechanical properties are needed. Full article

(This article belongs to the Special Issue Dental Materials)

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1262 KiB

Open AccessArticle

Role of Interphase in the Mechanical Behavior of Silica/Epoxy Resin Nanocomposites

by Yi Hua, Linxia Gu, Sundaralingam Premaraj and Xiaodong Zhang

Materials 2015, 8(6), 3519-3531; https://doi.org/10.3390/ma8063519 - 16 Jun 2015

Cited by 30 | Viewed by 6167

Abstract

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had [...] Read more.

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had significant influence on the effective stiffness of nanocomposites, while its sensitivities with respect to both the thickness and the gradient property of the interphase was minimal. The stiffer interphase demonstrated a higher load-sharing capacity, which also increased the stress distribution uniformity within the resin nanocomposites. Under the condition of imperfect interfacial bonding, the effective stiffness of nanocomposites was much lower, which was in good agreement with the documented experimental observations. This work could shed some light on the design and manufacturing of resin nanocomposites. Full article

(This article belongs to the Special Issue Dental Materials)

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1744 KiB

Open AccessArticle

Quantitative Analysis of Defects at the Dentin-Post Space in Endodontically Treated Teeth

by Mariasevera Di Comite, Vito Crincoli, Laura Fatone, Andrea Ballini, Giorgio Mori, Biagio Rapone, Antonio Boccaccio, Carmine Pappalettere, Felice Roberto Grassi and Angela Favia

Materials 2015, 8(6), 3268-3283; https://doi.org/10.3390/ma8063268 - 4 Jun 2015

Cited by 50 | Viewed by 6370

Abstract

The objective of this study was to assess frequency and extension of the defects affecting the dentin-post interface after using different combinations of irrigants and sealers. The experimental work was conducted on single-rooted teeth extracted for orthodontic reasons. The specimens were divided into [...] Read more.

The objective of this study was to assess frequency and extension of the defects affecting the dentin-post interface after using different combinations of irrigants and sealers. The experimental work was conducted on single-rooted teeth extracted for orthodontic reasons. The specimens were divided into different groups, according to irrigant and endodontic cement utilized, and endodontically instrumented. After fiberglass posts cementation, cross sections were obtained at apical, middle and coronal level of the root and submitted to quantitative analyses. Different types of defects were found: bubbles, bonding defects, polymerization defect, and cement residues. The percent extension of each defect and its frequency were related to the specific irrigant/sealer combination and to the root level. Detachments of the material from dentin were found only at apical and middle levels. Chlorhexidine digluconate seems to have more beneficial effects if compared to sodium hypochlorite: samples prepared with chlorhexidine digluconate showed a higher performance, with roots including null to few defects. In detail, samples treated with chlorhexidine digluconate and Pulp Canal Sealer showed the lowest frequency and the smallest dimension of defects. Full article

(This article belongs to the Special Issue Dental Materials)

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787 KiB

Open AccessArticle

Microleakage of Different Self-Adhesive Materials for Lithium Disilicate CAD/CAM Crowns

by Ella A. Naumova, Alexander Valta, Katharina Schaper, Wolfgang. H. Arnold and Andree Piwowarczyk

Materials 2015, 8(6), 3238-3253; https://doi.org/10.3390/ma8063238 - 3 Jun 2015

Cited by 1 | Viewed by 6153

Abstract

Objectives: To evaluate the microleakage and marginal gap of various luting materials after cementing ceramic crowns. Methods: Cervical margins of human molars were designed as circular chamfers. Cementation of full-contour ceramic crowns was conducted with zinc-phosphate cement (Harvard cement), resin cement (Panavia F [...] Read more.

Objectives: To evaluate the microleakage and marginal gap of various luting materials after cementing ceramic crowns. Methods: Cervical margins of human molars were designed as circular chamfers. Cementation of full-contour ceramic crowns was conducted with zinc-phosphate cement (Harvard cement), resin cement (Panavia F 2.0) and self-adhesive resin cements (RelyX Unicem, BifixSE, MaxCem Elite, PermaCem2.0, G-Cem). Aging of specimens was performed in artificial saliva, at 37 °C for four weeks and thermocycling. The marginal gap was measured with a scanning electron microscope and silver precipitation within the microleakage. All data were compared statistically. Results: Independent of the margin preparation, the highest median value for microleakage was 320.2 μm (Harvard cement), and the lowest was 0 μm (Panavia F 2.0). The median value for enamel was 0 µm and for dentin 270.9 μm (p < 0.001), which was independent of the luting material. The marginal and absolute marginal gaps were not significantly different between the tested materials. There was no correlation between microleakage and the marginal gaps. Conclusion: Significant differences in microleakage were found between the tested luting materials (p < 0.05). Independent from the luting materials, the microleakage in dentin showed significantly higher values than in enamel. Full article

(This article belongs to the Special Issue Dental Materials)

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4408 KiB

Open AccessArticle

Structural, Surface, in vitro Bacterial Adhesion and Biofilm Formation Analysis of Three Dental Restorative Composites

by Maria T. Azam, Abdul S. Khan, Danish Muzzafar, Rani Faryal, Saadat A. Siddiqi, Riaz Ahmad, Aqif A. Chauhdry and Ihtesham U. Rehman

Materials 2015, 8(6), 3221-3237; https://doi.org/10.3390/ma8063221 - 3 Jun 2015

Cited by 27 | Viewed by 7132

Abstract

This study was conducted to investigate the relationship between dental materials and bacterial adhesion on the grounds of their chemical composition and physical properties. Three commercially available dental restorative materials (Filtek™Z350, Filtek™P90 and Spectrum^®TPH^®) were structurally analyzed and their [...] Read more.

This study was conducted to investigate the relationship between dental materials and bacterial adhesion on the grounds of their chemical composition and physical properties. Three commercially available dental restorative materials (Filtek™Z350, Filtek™P90 and Spectrum^®TPH^®) were structurally analyzed and their wettability and surface roughness were evaluated by using Fourier Transform Infrared Spectroscopy, Contact Angle Measurement and Atomic Force Microscopy, respectively. These materials were molded into discs and tested with three bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia) for microbial attachment. The bacterial adhesion was observed at different time intervals, i.e., 0 h, 8 h, 24 h, 48 h and 72 h, along with Colony Forming Unit Count and Optical Density measurement of the media. It was found that all materials showed a degree of conversion with time intervals, i.e., 0 h, 8 h, 24 h, 48 h and 72 h, which led to the availability of functional groups (N–H and C–H) that might promote adhesion. The trend in difference in the extent of bacterial adhesion can be related to particle size, chemical composition and surface wettability of the dental materials. Full article

(This article belongs to the Special Issue Dental Materials)

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225 KiB

Open AccessArticle

Effect of Beverages on Viscoelastic Properties of Resin-Based Dental Composites

by Muhammad Kaleem, Abdul S. Khan, Ihtesham U. Rehman and Ferranti S. Wong

Materials 2015, 8(6), 2863-2872; https://doi.org/10.3390/ma8062863 - 26 May 2015

Cited by 5 | Viewed by 5390

Abstract

The viscoelastic properties of three commercially available resin-based composites (Filtek™ P60, Filtek™ Supreme, and Filtek™ Z250; 3M ESPE, Bracknell, UK) were measured to determine the effect of beverages on their storage moduli and damping ratios. Rectangular samples of the three hybrid composites were [...] Read more.

The viscoelastic properties of three commercially available resin-based composites (Filtek™ P60, Filtek™ Supreme, and Filtek™ Z250; 3M ESPE, Bracknell, UK) were measured to determine the effect of beverages on their storage moduli and damping ratios. Rectangular samples of the three hybrid composites were immersed in three beverages at 37 °C for 1, 7, 30, and 60 days. At each time interval, these samples were subjected to three-point bend tests in temperature mode using a Perkin Elmer DMA7 Dynamic Mechanical Analyzer (Perkin Elmer Corp., Waltham, MA, USA) to measure the storage modulus and damping ratio. The immersion time had significant influence on the viscoelastic property of composites and it was found that generally for all samples the storage modulus was reduced, whereas damping values increased with immersion time. The viscoelastic behavior of tested materials seems to be related to the pH environment, hydrophilicity and the chemical composition of composites. Full article

(This article belongs to the Special Issue Dental Materials)

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1262 KiB

Open AccessArticle

Combined Characterization of the Time Response of Impression Materials via Traditional and FTIR Measurements

by Giacomo Derchi, Enrico Manca, Amirreza Shayganpour, Antonio Barone, Alberto Diaspro and Marco Salerno

Materials 2015, 8(5), 2387-2399; https://doi.org/10.3390/ma8052387 - 6 May 2015

Cited by 4 | Viewed by 6024

Abstract

We investigated the temporal response of four dental impression materials, namely three siloxanes (Imprint 4, Flexitime, Aquasil) and one polyether (Impregum). The null hypothesis was that the nominal working times are confirmed by instrumental laboratory tests. We also aimed to identify alternative techniques [...] Read more.

We investigated the temporal response of four dental impression materials, namely three siloxanes (Imprint 4, Flexitime, Aquasil) and one polyether (Impregum). The null hypothesis was that the nominal working times are confirmed by instrumental laboratory tests. We also aimed to identify alternative techniques with strong physical-chemical background for the assessment of temporal response. Traditional characterization was carried out by shark fin test device and durometer at both ambient and body temperature. Additionally, Fourier-transform infrared spectroscopy was performed at room temperature. From shark fin height and Shore hardness versus time the working time and the setting time of the materials were evaluated, respectively. These were in reasonable agreement with the nominal values, except for Impregum, which showed longer working time. Spectroscopy confirmed the different character of the two types of materials, and provided for Imprint 4 and Aquasil an independent evaluation of both evolution times, consistent with the results of the other techniques. Shark fin test and durometer measurements showed deviations in setting time, low sensitivity to temperature for Flexitime, and longer working time at higher temperature for Impregum. Deviations of working time appear in operating conditions from what specified by the manufacturers. Fourier-transform infrared spectroscopy can provide insight in the correlation between material properties and their composition and structure. Full article

(This article belongs to the Special Issue Dental Materials)

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1987 KiB

Open AccessArticle

Impact of Packing and Processing Technique on Mechanical Properties of Acrylic Denture Base Materials

by Touraj Nejatian, Farshid Sefat and Tony Johnson

Materials 2015, 8(5), 2093-2109; https://doi.org/10.3390/ma8052093 - 24 Apr 2015

Cited by 18 | Viewed by 8028

Abstract

The fracture resistance of polymethylmethacrylate (PMMA) as the most popular denture base material is not satisfactory. Different factors can be involved in denture fracture. Among them, flexural fatigue and impact are the most common failure mechanisms of an acrylic denture base. It has [...] Read more.

The fracture resistance of polymethylmethacrylate (PMMA) as the most popular denture base material is not satisfactory. Different factors can be involved in denture fracture. Among them, flexural fatigue and impact are the most common failure mechanisms of an acrylic denture base. It has been shown that there is a correlation between the static strength and fatigue life of composite resins. Therefore, the transverse strength of the denture base materials can be an important indicator of their service life. In order to improve the fracture resistance of PMMA, extensive studies have been carried out; however, only a few promising results were achieved, which are limited to some mechanical properties of PMMA at the cost of other properties. This study aimed at optimizing the packing and processing condition of heat-cured PMMA as a denture base resin in order to improve its biaxial flexural strength (BFS). The results showed that the plain type of resin with a powder/monomer ratio of 2.5:1 or less, packed conventionally and cured in a water bath for 2 h at 95 °C provides the highest BFS. Also, it was found that the performance of the dry heat processor is inconsistent with the number of flasks being loaded. Full article

(This article belongs to the Special Issue Dental Materials)

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602 KiB

Open AccessArticle

Modification of pH Conferring Virucidal Activity on Dental Alginates

by Navina Nallamuthu, Michael Braden, John Oxford, David Williams and Mangala Patel

Materials 2015, 8(4), 1966-1975; https://doi.org/10.3390/ma8041966 - 21 Apr 2015

Cited by 9 | Viewed by 5586

Abstract

To formulate an alginate dental impression material with virucidal properties, experimental alginate dental impression materials were developed and the formulations adjusted in order to study the effect on pH profiles during setting. Commercially available materials served as a comparison. Eight experimental materials were [...] Read more.

To formulate an alginate dental impression material with virucidal properties, experimental alginate dental impression materials were developed and the formulations adjusted in order to study the effect on pH profiles during setting. Commercially available materials served as a comparison. Eight experimental materials were tested for antiviral activity against Herpes Simplex Virus type 1 (HSV-1). Changing the amount of magnesium oxide (MgO) used in the experimental formulations had a marked effect on pH. Increasing MgO concentration corresponded with increased pH values. All experimental materials brought about viral log reductions ranging between 0.5 and 4.0 over a period of 4 h. The material with the lowest pH was the most effective. The current work highlights the very important role of MgO in controlling pH profiles. This knowledge has been applied to the formulation of experimental alginates; where materials with pH values of approximately 4.2–4.4 are able to achieve a significant log reduction when assayed against HSV-1. Full article

(This article belongs to the Special Issue Dental Materials)

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1412 KiB

Open AccessArticle

Effect of Different Luting Agents on the Retention of Lithium Disilicate Ceramic Crowns

by Nicola Mobilio, Alberto Fasiol, Francesco Mollica and Santo Catapano

Materials 2015, 8(4), 1604-1611; https://doi.org/10.3390/ma8041604 - 7 Apr 2015

Cited by 15 | Viewed by 6654

Abstract

No studies are available that evaluate the retention of disilicate crowns according to different cementation procedures. The purpose of this study was to measure the retention of lithium disilicate crowns cemented using two different cementation systems. Twenty extracted mandibular premolars were prepared. Anatomic [...] Read more.

No studies are available that evaluate the retention of disilicate crowns according to different cementation procedures. The purpose of this study was to measure the retention of lithium disilicate crowns cemented using two different cementation systems. Twenty extracted mandibular premolars were prepared. Anatomic crowns were waxed and hot pressed using lithium disilicate ceramic. Teeth were divided into two groups (n = 10): (1) self-curing luting composite and (2) glass-ionomer cement (GIC). After cementation, the crowns were embedded in acrylic resin block with a screw base. Each specimen was pulled along the path of insertion in Universal Testing Machine. Failure load in Newtons (N) and failure mode were recorded for each specimen. Failure mode was classified as decementation or fracture. Failure load data were analyzed using one-way analysis of variance (ANOVA). Failure modes were compared using Pearson’s Chi-square test. Mean failure load was 306.6(±193.8) N for composite group and 94.7(±48.2) N for GIC group (p = 0.004). Disilicate crown cemented with luting composite most often failed by fracture; otherwise, crown cemented with glass-ionomer cement most often failed by decementation (p = 0.02). Disilicate full crown cemented with luting composite showed higher failure load compared with conventional cementation with glass-ionomer cement. Full article

(This article belongs to the Special Issue Dental Materials)

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1032 KiB

Open AccessArticle

All-Ceramic Single Crown Restauration of Zirconia Oral Implants and Its Influence on Fracture Resistance: An Investigation in the Artificial Mouth

by Ralf-Joachim Kohal, Jolanta Bernadette Kilian, Susanne Stampf and Benedikt Christopher Spies

Materials 2015, 8(4), 1577-1589; https://doi.org/10.3390/ma8041577 - 1 Apr 2015

Cited by 21 | Viewed by 7110

Abstract

The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples) and without [...] Read more.

The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples) and without crowns (N, 24 samples) were subdivided according to the loading protocol, resulting in three groups of 8 samples each: Group “0” was not exposed to cyclic loading, whereas groups “5” and “10” were loaded with 5 and 10 million chewing cycles, respectively. This resulted in 6 different groups: C0/N0, C5/N5 and C10/N10. Subsequently, all 48 implants were statically loaded to fracture and bending moments were calculated. All implants survived the artificial aging. For the static loading the following average bending moments were calculated: C0: 326 Ncm; C5: 339 Ncm; C10: 369 Ncm; N0: 339 Ncm; N5: 398 Ncm and N10: 355 Ncm. To a certain extent, thermomechanical cycling resulted in an increase of fracture resistance which did not prove to be statistically significant. Regarding its fracture resistance, the evaluated ceramic implant system made of Y-TZP seems to be able to resist physiological chewing forces long-term. Restauration with all-ceramic single crowns showed no negative influence on fracture resistance. Full article

(This article belongs to the Special Issue Dental Materials)

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2413 KiB

Open AccessArticle

Nanostructured Titanium-10 wt% 45S5 Bioglass-Ag Composite Foams for Medical Applications

by Karolina Jurczyk, Grzegorz Adamek, Marcelina M. Kubicka, Jaroslaw Jakubowicz and Mieczyslaw Jurczyk

Materials 2015, 8(4), 1398-1412; https://doi.org/10.3390/ma8041398 - 25 Mar 2015

Cited by 15 | Viewed by 6709

Abstract

The article presents an investigation on the effectiveness of nanostructured titanium-10 wt% 45S5 Bioglass-1 wt% Ag composite foams as a novel class of antibacterial materials for medical applications. The Ti-based composite foams were prepared by the combination of mechanical alloying and a “space-holder” [...] Read more.

The article presents an investigation on the effectiveness of nanostructured titanium-10 wt% 45S5 Bioglass-1 wt% Ag composite foams as a novel class of antibacterial materials for medical applications. The Ti-based composite foams were prepared by the combination of mechanical alloying and a “space-holder” sintering process. In the first step, the Ti-10 wt% 45S5 Bioglass-1 wt% Ag powder synthesized by mechanical alloying and annealing mixed with 1.0 mm diameter of saccharose crystals was finally compacted in the form of pellets. In the next step, the saccharose crystals were dissolved in water, leaving open spaces surrounded by metallic-bioceramic scaffold. The sintering of the scaffold leads to foam formation. It was found that 1:1 Ti-10 wt% 45S5 Bioglass-1 wt% Ag/sugar ratio leads to porosities of about 70% with pore diameter of about 0.3–1.1 mm. The microstructure, corrosion resistance in Ringer’s solution of the produced foams were investigated. The value of the compression strength for the Ti-10 wt% 45S5 Bioglass-1 wt% Ag foam with 70% porosity was 1.5 MPa and the Young’s modulus was 34 MPa. Silver modified Ti-10 wt% 45S5 Bioglass composites possess excellent antibacterial activities against Staphylococcus aureus. Porous Ti-10 wt% 45S5 Bioglass-1 wt% foam could be a possible candidate for medical implants applications. Full article

(This article belongs to the Special Issue Dental Materials)

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4463 KiB

Open AccessArticle

Comparative Study of Structure-Property Relationships in Polymer Networks Based on Bis-GMA, TEGDMA and Various Urethane-Dimethacrylates

by Izabela Barszczewska-Rybarek and Sebastian Jurczyk

Materials 2015, 8(3), 1230-1248; https://doi.org/10.3390/ma8031230 - 19 Mar 2015

Cited by 37 | Viewed by 8821

Abstract

The effect of various dimethacrylates on the structure and properties of homo- and copolymer networks was studied. The 2,2-bis-[4-(2-hydroxy-3- methacryloyloxypropoxy)phenyl]-propane) (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and 1,6-bis-(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane (HEMA/TMDI), all popular in dentistry, as well as five urethane-dimethacrylate (UDMA) alternatives of HEMA/TMDI were used [...] Read more.

The effect of various dimethacrylates on the structure and properties of homo- and copolymer networks was studied. The 2,2-bis-[4-(2-hydroxy-3- methacryloyloxypropoxy)phenyl]-propane) (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and 1,6-bis-(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane (HEMA/TMDI), all popular in dentistry, as well as five urethane-dimethacrylate (UDMA) alternatives of HEMA/TMDI were used as monomers. UDMAs were obtained from mono-, di- and tri(ethylene glycol) monomethacrylates and various commercial diisocyanates. The chemical structure, degree of conversion (DC) and scanning electron microscopy (SEM) fracture morphology were related to the mechanical properties of the polymers: flexural strength and modulus, hardness, as well as impact strength. Impact resistance was widely discussed, being lower than expected in the case of poly(UDMA)s. It was caused by the heterogeneous morphology of these polymers and only moderate strength of hydrogen bonds between urethane groups, which was not high enough to withstand high impact energy. Bis-GMA, despite having the highest polymer morphological heterogeneity, ensured fair impact resistance, due to having the strongest hydrogen bonds between hydroxyl groups. The TEGDMA homopolymer, despite being heterogeneous, produced the smoothest morphology, which resulted in the lowest brittleness. The UDMA monomer, having diethylene glycol monomethacrylate wings and the isophorone core, could be the most suitable HEMA/TMDI alternative. Its copolymer with Bis-GMA and TEGDMA had improved DC as well as all the mechanical properties. Full article

(This article belongs to the Special Issue Dental Materials)

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1582 KiB

Open AccessArticle

Combined Effect of a Microporous Layer and Type I Collagen Coating on a Biphasic Calcium Phosphate Scaffold for Bone Tissue Engineering

by Mun-Hwan Lee, Changkook You and Kyo-Han Kim

Materials 2015, 8(3), 1150-1161; https://doi.org/10.3390/ma8031150 - 16 Mar 2015

Cited by 31 | Viewed by 7637

Abstract

In this study, type I collagen was coated onto unmodified and modified microporous biphasic calcium phosphate (BCP) scaffolds. Surface characterization using a scanning electron microscope (SEM) and a surface goniometer confirmed the modification of the BCP coating. The quantity of the collagen coating [...] Read more.

In this study, type I collagen was coated onto unmodified and modified microporous biphasic calcium phosphate (BCP) scaffolds. Surface characterization using a scanning electron microscope (SEM) and a surface goniometer confirmed the modification of the BCP coating. The quantity of the collagen coating was investigated using Sirius Red staining, and quantitative assessment of the collagen coating showed no significant differences between the two groups. MG63 cells were used to evaluate cell proliferation and ALP activity on the modified BCP scaffolds. The modified microporous surfaces showed low contact angles and large surface areas, which enhanced cell spreading and proliferation. Coating of the BCP scaffolds with type I collagen led to enhanced cell-material interactions and improved MG63 functions, such as spreading, proliferation, and differentiation. The micropore/collagen-coated scaffold showed the highest rate of cell response. These results indicate that a combination of micropores and collagen enhances cellular function on bioengineered bone allograft tissue. Full article

(This article belongs to the Special Issue Dental Materials)

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1646 KiB

Open AccessArticle

Improved Resin–Zirconia Bonding by Room Temperature Hydrofluoric Acid Etching

by Mun-Hwan Lee, Jun Sik Son, Kyo-Han Kim and Tae-Yub Kwon

Materials 2015, 8(3), 850-866; https://doi.org/10.3390/ma8030850 - 2 Mar 2015

Cited by 23 | Viewed by 8924

Abstract

This in vitro study was conducted to evaluate the shear bond strength of “non-self-adhesive” resin to dental zirconia etched with hydrofluoric acid (HF) at room temperature and to compare it to that of air-abraded zirconia. Sintered zirconia plates were air-abraded (control) or etched [...] Read more.

This in vitro study was conducted to evaluate the shear bond strength of “non-self-adhesive” resin to dental zirconia etched with hydrofluoric acid (HF) at room temperature and to compare it to that of air-abraded zirconia. Sintered zirconia plates were air-abraded (control) or etched with 10%, 20%, or 30% HF for either 5 or 30 min. After cleaning, the surfaces were characterized using various analytical techniques. Three resin cylinders (Duo-Link) were bonded to each treated plate. All bonded specimens were stored in water at 37 °C for 24 h, and then half of them were additionally thermocycled 5000 times prior to the shear bond-strength tests (n = 12). The formation of micro- and nano-porosities on the etched surfaces increased with increasing concentration and application time of the HF solution. The surface wettability of zirconia also increased with increasing surface roughness. Higher concentrations and longer application times of the HF solution produced higher bond-strength values. Infiltration of the resin into the micro- and nano-porosities was observed by scanning electron microscopy. This in vitro study suggests that HF slowly etches zirconia ceramic surfaces at room temperature, thereby improving the resin–zirconia bond strength by the formation of retentive sites. Full article

(This article belongs to the Special Issue Dental Materials)

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3145 KiB

Open AccessArticle

Enhanced Hydrophilicity and Biocompatibility of Dental Zirconia Ceramics by Oxygen Plasma Treatment

by Ching-Chou Wu, Chung-Kai Wei, Chia-Che Ho and Shinn-Jyh Ding

Materials 2015, 8(2), 684-699; https://doi.org/10.3390/ma8020684 - 16 Feb 2015

Cited by 67 | Viewed by 9735

Abstract

Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1) to characterize changes in surface properties of zirconia (ZrO₂) ceramic after oxygen plasma treatment; and (2) to determine the effect of [...] Read more.

Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1) to characterize changes in surface properties of zirconia (ZrO₂) ceramic after oxygen plasma treatment; and (2) to determine the effect of such changes on biological responses of human osteoblast-like cells (MG63). The results indicated that the surface morphology was not changed by oxygen plasma treatment. In contrast, oxygen plasma treatment to ZrO₂ not only resulted in an increase in hydrophilicity, but also it retained surface hydrophilicity after 5-min treatment time. More importantly, surface properties of ZrO₂ modified by oxygen plasma treatment were beneficial for cell growth, whereas the surface roughness of the materials did not have a significant efficacy. It is concluded that oxygen plasma treatment was certified to be effective in modifying the surface state of ZrO₂ and has the potential in the creation and maintenance of hydrophilic surfaces and the enhancement of cell proliferation and differentiation. Full article

(This article belongs to the Special Issue Dental Materials)

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2446 KiB

Open AccessArticle

A New Method Combining Finite Element Analysis and Digital Image Correlation to Assess Macroscopic Mechanical Properties of Dentin

by Wenlong Wang, Nicolas Roubier, Guillaume Puel, Jean-Marc Allain, Ingrid C. Infante, Jean-Pierre Attal and Elsa Vennat

Materials 2015, 8(2), 535-550; https://doi.org/10.3390/ma8020535 - 6 Feb 2015

Cited by 11 | Viewed by 10964

Abstract

A literature review points out a large discrepancy in the results of the mechanical tests on dentin that can be explained by stress and strain assessment during the tests. Errors in these assessments during mechanical tests can lead to inaccurate estimation of the [...] Read more.

A literature review points out a large discrepancy in the results of the mechanical tests on dentin that can be explained by stress and strain assessment during the tests. Errors in these assessments during mechanical tests can lead to inaccurate estimation of the mechanical properties of the tested material. On top of that, using the beam theory to analyze the bending test for thick specimens will increase these experimental errors. After summarizing the results of mechanical tests on dentin in the literature, we focus on bending tests and compare the stress assessment obtained by finite element analysis (FEA) and by beam theory application. We show that the difference between the two methods can be quite large in some cases, leading us to prefer the use of FEA to assess stresses. We then propose a new method based on coupling finite element analysis and digital image correlation (DIC) to more accurately evaluate stress distributions, strain distributions and elastic modulus in the case of a three-point bending test. To illustrate and prove the feasibility of the method, it is applied on a dentinal sample so that mean elastic modulus and maximum tensile stress are obtained (11.9 GPa and 143.9 MPa). Note that the main purpose of this study is to focus on the method itself, and not to provide new mechanical values for dentin. When used in standard mechanical testing of dentin, this kind of method should help to narrow the range of obtained mechanical properties values. Full article

(This article belongs to the Special Issue Dental Materials)

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The Use of Quaternary Ammonium to Combat Dental Caries

by Yang Ge, Suping Wang, Xuedong Zhou, Haohao Wang, Hockin H. K. Xu and Lei Cheng

Materials 2015, 8(6), 3532-3549; https://doi.org/10.3390/ma8063532 - 17 Jun 2015

Cited by 54 | Viewed by 8741

Abstract

Resin composites and adhesives are increasingly popular in dental restorations, but secondary caries is one of the main reasons for restoration failure. Quaternary ammonium monomers (QAMs) have an anti-microbial effect and are widely used in many fields. Since the concept of the immobilized [...] Read more.

Resin composites and adhesives are increasingly popular in dental restorations, but secondary caries is one of the main reasons for restoration failure. Quaternary ammonium monomers (QAMs) have an anti-microbial effect and are widely used in many fields. Since the concept of the immobilized antibacterial effect was put forward, dental restorations containing QAMs have been studied to reduce secondary caries. Previous studies have been struggling to develop novel anti-caries materials which might have triple benefits: good mechanical properties, antibacterial effects and remineralization potentials. Different kinds of QAMs have been proven to be effective in inhibiting the growth and metabolism of biofilms. Combination of QAMs and other nanoparticles in resin composites and adhesives could enhance their anti-caries capability. Therefore, QAMs are promising to show significant impact on the future of restorative and preventive dentistry. Full article

(This article belongs to the Special Issue Dental Materials)

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Biofilm and Dental Biomaterials

by Marit Øilo and Vidar Bakken

Materials 2015, 8(6), 2887-2900; https://doi.org/10.3390/ma8062887 - 26 May 2015

Cited by 69 | Viewed by 15865

Abstract

All treatment involving the use of biomaterials in the body can affect the host in positive or negative ways. The microbiological environment in the oral cavity is affected by the composition and shape of the biomaterials used for oral restorations. This may impair [...] Read more.

All treatment involving the use of biomaterials in the body can affect the host in positive or negative ways. The microbiological environment in the oral cavity is affected by the composition and shape of the biomaterials used for oral restorations. This may impair the patients’ oral health and sometimes their general health as well. Many factors determine the composition of the microbiota and the formation of biofilm in relation to biomaterials such as, surface roughness, surface energy and chemical composition, This paper aims to give an overview of the scientific literature regarding the association between the chemical, mechanical and physical properties of dental biomaterials and oral biofilm formation, with emphasis on current research and future perspectives. Full article

(This article belongs to the Special Issue Dental Materials)

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Bone Regeneration Using Bone Morphogenetic Proteins and Various Biomaterial Carriers

by Zeeshan Sheikh, Mohammad Ahmad Javaid, Nader Hamdan and Raheel Hashmi

Materials 2015, 8(4), 1778-1816; https://doi.org/10.3390/ma8041778 - 15 Apr 2015

Cited by 79 | Viewed by 11895

Abstract

Trauma and disease frequently result in fractures or critical sized bone defects and their management at times necessitates bone grafting. The process of bone healing or regeneration involves intricate network of molecules including bone morphogenetic proteins (BMPs). BMPs belong to a larger superfamily [...] Read more.

Trauma and disease frequently result in fractures or critical sized bone defects and their management at times necessitates bone grafting. The process of bone healing or regeneration involves intricate network of molecules including bone morphogenetic proteins (BMPs). BMPs belong to a larger superfamily of proteins and are very promising and intensively studied for in the enhancement of bone healing. More than 20 types of BMPs have been identified but only a subset of BMPs can induce de novo bone formation. Many research groups have shown that BMPs can induce differentiation of mesenchymal stem cells and stem cells into osteogenic cells which are capable of producing bone. This review introduces BMPs and discusses current advances in preclinical and clinical application of utilizing various biomaterial carriers for local delivery of BMPs to enhance bone regeneration. Full article

(This article belongs to the Special Issue Dental Materials)

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Advances in Nanotechnology for Restorative Dentistry

by Zohaib Khurshid, Muhammad Zafar, Saad Qasim, Sana Shahab, Mustafa Naseem and Ammar AbuReqaiba

Materials 2015, 8(2), 717-731; https://doi.org/10.3390/ma8020717 - 16 Feb 2015

Cited by 184 | Viewed by 28763

Abstract

Rationalizing has become a new trend in the world of science and technology. Nanotechnology has ascended to become one of the most favorable technologies, and one which will change the application of materials in different fields. The quality of dental biomaterials has been [...] Read more.

Rationalizing has become a new trend in the world of science and technology. Nanotechnology has ascended to become one of the most favorable technologies, and one which will change the application of materials in different fields. The quality of dental biomaterials has been improved by the emergence of nanotechnology. This technology manufactures materials with much better properties or by improving the properties of existing materials. The science of nanotechnology has become the most popular area of research, currently covering a broad range of applications in dentistry. This review describes the basic concept of nanomaterials, recent innovations in nanomaterials and their applications in restorative dentistry. Advances in nanotechnologies are paving the future of dentistry, and there are a plenty of hopes placed on nanomaterials in terms of improving the health care of dental patients. Full article

(This article belongs to the Special Issue Dental Materials)

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