Materials

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14 pages, 1178 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Color Stability, Water Sorption, and Solubility of Current Resin Composites

by Wenkai Huang, Ling Ren, Yuyao Cheng, Minghua Xu, Wenji Luo, Desong Zhan, Hidehiko Sano and Jiale Fu

Materials 2022, 15(19), 6710; https://doi.org/10.3390/ma15196710 - 27 Sep 2022

Cited by 20 | Viewed by 2777

Abstract

This study aims to assess the color stability, water sorption, and solubility of 11 resin composites as commercially available dental products. Twenty samples (10 mm in diameter and 2 mm in thickness) of each material were fabricated using a customized silicone mold, followed [...] Read more.

This study aims to assess the color stability, water sorption, and solubility of 11 resin composites as commercially available dental products. Twenty samples (10 mm in diameter and 2 mm in thickness) of each material were fabricated using a customized silicone mold, followed by immersion in each of curry, coffee, wine, and distilled water for 28 days (n = 5). Baseline shade and color changes (ΔE) were measured using a reflection spectrophotometer. The CIE L*, a*, b* system was used to evaluate the color changes. Five samples of each resin composite were applied to test water sorption and solubility according to ISO 4049:2009. As a result, the ∆E values were significantly influenced by each of the three factors (composition of material, solution, time) and the interactions between them (p < 0.001). Highest resistance to discoloration was achieved by Ceram.X One Universal (CXU), followed by Magnafill Putty (MP). Generally, microhybrid composites showed fewer color changes than nanohybrid composites and giomers. DX. Universal and Filtek Z350 XT showed the highest ΔE values in all colorants. All materials tested in this study fulfilled the criteria of ISO 4049:2009; CXU and MP had the lowest water sorption and solubility. The Pearson test showed statistically significant positive correlations between water sorption and ΔE and between solubility and ΔE. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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9 pages, 1933 KiB

Open AccessCommunication

Evaluation of New Hollow Sleeve Composites for Direct Post-Core Construction

by Shinji Yoshii, Sufyan Garoushi, Chiaki Kitamura, Pekka K. Vallittu and Lippo V. Lassila

Materials 2021, 14(23), 7397; https://doi.org/10.3390/ma14237397 - 2 Dec 2021

Cited by 2 | Viewed by 1673

Abstract

The preset shape and diameter of a prefabricated FRC post rarely follows the anatomy of the root canal. To solve this problem, a new hollow sleeve composite (HSC) system for post-core construction was developed and characterized. A woven fiber was impregnated with two [...] Read more.

The preset shape and diameter of a prefabricated FRC post rarely follows the anatomy of the root canal. To solve this problem, a new hollow sleeve composite (HSC) system for post-core construction was developed and characterized. A woven fiber was impregnated with two types of resins: Bis-GMA or PMMA, and rolled into cylinders with outer diameter of 2 mm and two different inner diameters, namely 1.2 or 1.5 mm. The commercial i-TFC system was used as a control. Dual-cure resin composite was injected into these sleeves. Additionally, conventional solid fiber post was used as the inner part of the sleeve. The three-point bending test was used to measure the mechanical properties of the specimens and the fracture surface was examined using an electron microscope (SEM). The HSC (1.5 mm, Bis-GMA) revealed a statistically similar flexural modulus but higher flexural strength (437 MPa) compared to i-TFC (239 MPa; ANOVA, p < 0.05). When a fiber post was added inside, all values had a tendency to increase. After hydrothermal accelerated aging, the majority of specimens showed a significant (p < 0.05) decrease in flexural strength and modulus. SEM fracture analysis confirmed that the delamination occurred at the interface between the outer and inner materials. The HSC system provided flexibility but still high mechanical values compared to the commercial system. Thus, this system might offer an alternative practical option for direct post-core construction. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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11 pages, 1739 KiB

Open AccessArticle

3D-Printed vs. Heat-Polymerizing and Autopolymerizing Denture Base Acrylic Resins

by Leila Perea-Lowery, Mona Gibreel, Pekka K. Vallittu and Lippo V. Lassila

Materials 2021, 14(19), 5781; https://doi.org/10.3390/ma14195781 - 3 Oct 2021

Cited by 68 | Viewed by 4964

Abstract

The aim of this work was to investigate the effect of two post-curing methods on the mechanical properties of a 3D-printed denture base material. Additionally, to compare the mechanical properties of that 3D-printed material with those of conventional autopolymerizing and a heat-cured denture [...] Read more.

The aim of this work was to investigate the effect of two post-curing methods on the mechanical properties of a 3D-printed denture base material. Additionally, to compare the mechanical properties of that 3D-printed material with those of conventional autopolymerizing and a heat-cured denture base material. A resin for 3D-printing denture base (Imprimo^®), a heat-polymerizing acrylic resin (Paladon^® 65), and an autopolymerizing acrylic resin (Palapress^®) were investigated. Flexural strength, elastic modulus, fracture toughness, work of fracture, water sorption, and water solubility were evaluated. The 3D-printed test specimens were post-cured using two different units (Imprimo Cure^® and Form Cure^®). The tests were carried out after both dry and 30 days water storage. Data were collected and statistically analyzed. Resin type had a significant effect on the flexural strength, elastic modulus, fracture toughness, and work of fracture (p < 0.001). The flexural strength and elastic modulus for the heat-cured polymer were significantly the highest among all investigated groups regardless of the storage condition (p < 0.001). The fracture toughness and work of fracture of the 3D-printed material were significantly the lowest (p < 0.001). The heat-cured polymer had the lowest significant water solubility (p < 0.001). The post-curing method had an impact on the flexural strength of the investigated 3D-printed denture base material. The flexural strength, elastic modulus, fracture toughness, work of fracture of the 3D-printed material were inferior to those of the heat-cured one. Increased post-curing temperature may enhance the flexural properties of resin monomers used for 3D-printing dental appliances. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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17 pages, 2734 KiB

Open AccessArticle

Characterisation of Microparticle Waste from Dental Resin-Based Composites

by Steven Mulligan, Jesús J. Ojeda, Gabriella Kakonyi, Steven F. Thornton, Keyvan Moharamzadeh and Nicolas Martin

Materials 2021, 14(16), 4440; https://doi.org/10.3390/ma14164440 - 8 Aug 2021

Cited by 9 | Viewed by 3099

Abstract

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste. Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function [...] Read more.

Clinical applications of resin-based composite (RBC) generate environmental pollution in the form of microparticulate waste. Methods: SEM, particle size and specific surface area analysis, FT-IR and potentiometric titrations were used to characterise microparticles arising from grinding commercial and control RBCs as a function of time, at time of generation and after 12 months ageing in water. The RBCs were tested in two states: (i) direct-placement materials polymerised to simulate routine clinical use and (ii) pre-polymerised CAD/CAM ingots milled using CAD/CAM technology. Results: The maximum specific surface area of the direct-placement commercial RBC was seen after 360 s of agitation and was 1290 m²/kg compared with 1017 m²/kg for the control material. The median diameter of the direct-placement commercial RBC was 6.39 μm at 360 s agitation and 9.55 μm for the control material. FTIR analysis confirmed that microparticles were sufficiently unique to be identified after 12 months ageing and consistent alteration of the outermost surfaces of particles was observed. Protonation-deprotonation behaviour and the pH of zero proton charge (pH_zpc) ≈ 5–6 indicated that the particles are negatively charged at neutral pH7. Conclusion: The large surface area of RBC microparticles allows elution of constituent monomers with potential environmental impacts. Characterisation of this waste is key to understanding potential mitigation strategies. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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13 pages, 2559 KiB

Open AccessArticle

Enhancing Toughness and Reducing Volumetric Shrinkage for Bis-GMA/TEGDMA Resin Systems by Using Hyperbranched Thiol Oligomer HMDI-6SH

by Biao Yu, Jingwei He, Sufyan Garoushi, Pekka K. Vallittu and Lippo Lassila

Materials 2021, 14(11), 2817; https://doi.org/10.3390/ma14112817 - 25 May 2021

Cited by 8 | Viewed by 2332

Abstract

In order to improve the toughness and reduce polymerization shrinkage of traditional bisphenol A-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based dental resin system, a hyperbranched thiol oligomer (HMDI-6SH) was synthesized via thiol-isocyanate click reaction using pentaerythritol tetra(3-mercaptopropionate (PETA) and dicyclohexylmethane 4,4′-diisocyanate (HMDI) as [...] Read more.

In order to improve the toughness and reduce polymerization shrinkage of traditional bisphenol A-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based dental resin system, a hyperbranched thiol oligomer (HMDI-6SH) was synthesized via thiol-isocyanate click reaction using pentaerythritol tetra(3-mercaptopropionate (PETA) and dicyclohexylmethane 4,4′-diisocyanate (HMDI) as raw materials. Then HMDI-6SH was mixed with 1,3,5-Triallyl-1,3,5-Triazine-2,4,6(1H,3H,5H)-Trione (TTT) to prepare thiol-ene monomer systems, which were added into Bis-GMA/TEGDMA resins with different mass ratio from 10 wt% to 40 wt% to serve as anti-shrinking and toughening agent. The physicochemical properties of these thiol-ene-methacrylate ternary resins including functional groups conversion, volumetric shrinkage, flexural properties, water sorption, and water solubility were evaluated. The results showed that the incorporation of HMDI/TTT monomer systems into Bis-GMA/TEGDMA based resin could improve C=C double bond conversion from 62.1% to 82.8% and reduced volumetric shrinkage from 8.53% to 4.92%. When the mass fraction of HMDI/TTT monomer systems in the resins was no more than 20 wt%, the flexural strength of the resin was higher or comparable to Bis-GMA/TEGDMA based resins (p > 0.05). The toughness (it was measured from the stress–strain curves of three-point bending test) of the resins was improved. Water sorption and water solubility tests showed that the hydrophobicity of resin was enhanced with increasing the content of thioester moiety in resin. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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11 pages, 4004 KiB

Open AccessCommunication

Effect of Accelerated Aging on Some Mechanical Properties and Wear of Different Commercial Dental Resin Composites

by Jonne Oja, Lippo Lassila, Pekka K. Vallittu and Sufyan Garoushi

Materials 2021, 14(11), 2769; https://doi.org/10.3390/ma14112769 - 23 May 2021

Cited by 25 | Viewed by 3124

Abstract

The aim of current in vitro research was to determine the effect of hydrothermal accelerated aging on the mechanical properties and wear of different commercial dental resin composites (RCs). In addition, the effect of expiration date of the composite prior its use was [...] Read more.

The aim of current in vitro research was to determine the effect of hydrothermal accelerated aging on the mechanical properties and wear of different commercial dental resin composites (RCs). In addition, the effect of expiration date of the composite prior its use was also evaluated. Five commercially available RCs were studied: Conventional RCs (Filtek Supreme XTE, G-aenial Posterior, Denfil, and >3y expired Supreme XTE), bulk-fill RC (Filtek Bulk Fill), and short fiber-reinforced RC (everX Posterior). Three-point flexural test was used for determination of ultimate flexural strength (n = 8). A vickers indenter was used for testing surface microhardness. A wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. Wear pattern was analyzed by a three-dimensional (3D) noncontact optical profilometer. Degree of C=C bond conversion of monomers was determined by FTIR-spectrometry. The specimens were either dry stored for 48 h (37 °C) or boiled (100 °C) for 16 h before testing. Scanning electron microscopy (SEM) was used to evaluate the microstructure of each material. Data were analyzed using ANOVA (p = 0.05). Hydrothermal aging had no significant effects on the surface wear and microhardness of tested RCs (p > 0.05). While flexural strength significantly decreased after aging (p < 0.05), except for G-aenial Posterior, which showed no differences. The lowest average wear depth was found for Filtek Bulk Fill (29 µm) (p < 0.05), while everX Posterior and Denfil showed the highest wear depth values (40, 39 µm) in both conditions. Passing the expiration date for 40 months did not affect the flexural strength and wear of tested RC. SEM demonstrated a significant number of small pits on Denfil’s surface after aging. It was concluded that the effect of accelerated aging may have caused certain weakening of the RC of some brands, whereas no effect was found with one brand of RC. Thus, the accelerated aging appeared to be more dependent on material and tested material property. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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11 pages, 29261 KiB

Open AccessArticle

The Effect of Material Type and Location of an Orthodontic Retainer in Resisting Axial or Buccal Forces

by Jaana Ohtonen, Lippo Lassila, Eija Säilynoja and Pekka K. Vallittu

Materials 2021, 14(9), 2319; https://doi.org/10.3390/ma14092319 - 29 Apr 2021

Cited by 7 | Viewed by 2087

Abstract

The purpose of this study was to investigate the effect of retainer material and retainer position on a tooth to resist movement of the tooth in a simulation model. Bidirectional continuous glass fiber-reinforced composite (FRC) retainers and control retainers of steel wires were [...] Read more.

The purpose of this study was to investigate the effect of retainer material and retainer position on a tooth to resist movement of the tooth in a simulation model. Bidirectional continuous glass fiber-reinforced composite (FRC) retainers and control retainers of steel wires were tested. The FRC retainers had a polymer matrix of bisphenol-A-glycidyldimethacrylate (bis-GMA) and poly(methylmethacrylate) (PMMA), and it was cured with a photoinitiator system. The retainers were adhered to a lower jaw Frasaco model in two different positions. Resistance against the movement of one tooth was measured from two directions. The average load values within the FRC retainer groups were higher than within the metal retainer groups. The load values for the groups loaded from the axial direction were higher than those loaded from the buccal direction. FRC retainers, which were located 1–2 mm from the incisal edge, showed higher load values than those located 4–5 mm from the incisal edge. There was a significant difference in load values between FRC retainers and metal retainers (p < 0.01). The wire position and the direction of force also had significant effects (p < 0.01). There were no significant differences between metal retainer groups. The results of this study suggest that metal retainers are more flexible, allowing for tooth movements of larger magnitude than with FRC retainers. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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Graphical abstract

15 pages, 3606 KiB

Open AccessArticle

Characterisation of the Filler Fraction in CAD/CAM Resin-Based Composites

by Andreas Koenig, Julius Schmidtke, Leonie Schmohl, Sibylle Schneider-Feyrer, Martin Rosentritt, Hieronymus Hoelzig, Gert Kloess, Ketpat Vejjasilpa, Michaela Schulz-Siegmund, Florian Fuchs and Sebastian Hahnel

Materials 2021, 14(8), 1986; https://doi.org/10.3390/ma14081986 - 15 Apr 2021

Cited by 24 | Viewed by 3384

Abstract

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary [...] Read more.

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material’s mechanical and optical properties. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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14 pages, 2101 KiB

Open AccessArticle

Effect of Two Immediate Dentin Sealing Approaches on Bond Strength of Lava™ CAD/CAM Indirect Restoration

by Hassan Faez Abdullah Gailani, Cristina Benavides-Reyes, María Victoria Bolaños-Carmona, Eva Rosel-Gallardo, Purificación González-Villafranca and Santiago González-López

Materials 2021, 14(7), 1629; https://doi.org/10.3390/ma14071629 - 26 Mar 2021

Cited by 9 | Viewed by 3337

Abstract

The objective of this work was to compare the micro-tensile bond strength (µTBS) of CAD/CAM (Computer-Aided Design/ Computer-Aided Manufacturing) specimens cemented with different pairing of adhesives and resin-cements using two Immediate Dentin Dealing (IDS) approaches in comparison with Delay Dentin Sealing (DDS). Coronal [...] Read more.

The objective of this work was to compare the micro-tensile bond strength (µTBS) of CAD/CAM (Computer-Aided Design/ Computer-Aided Manufacturing) specimens cemented with different pairing of adhesives and resin-cements using two Immediate Dentin Dealing (IDS) approaches in comparison with Delay Dentin Sealing (DDS). Coronal dentin from 108 molars were divided into nine groups (n = 12) depending on the adhesive/resin-cement (A-C) assigned. Lava™ Ultimate (4 × 10 × 10 mm) was cemented according to different strategies: IDS1(cementation after dentin sealing), DDS (dentin sealing and cementation at 2-weeks), IDS2 (immediate dentin sealing and cementation at 2-weeks). Samples were sectioned and tested until failure to determine the µTBS. Failure mode was categorized as dentin/cement (DC), at Lava™ Ultimate/cement (LC) and hybrid (H). Kruskal–Wallis and Mann–Whitney U tests and influence of the type of failure on the µTBS by survival analysis with competing risk was explored. Mostly, µTBS values were equal or higher in IDS2 than DDS. In general, A-Cs that showed higher µTBS, have high percentages of LC failure. Survival analysis with competing risk between DC + H and LC values showed that some A-Cs would significantly increase the µTBS values for IDS2. A-Cs with the highest adhesion values showed a high percentage of fractures at the LC interface, suggesting that the adhesion at the adhesive/dentin interface would be higher. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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10 pages, 3005 KiB

Open AccessArticle

Surface Integrity of Dimethacrylate Composite Resins with Low Shrinkage Comonomers

by Jingwei He, Sufyan Garoushi, Eija Säilynoja, Pekka Vallittu and Lippo Lassila

Materials 2021, 14(7), 1614; https://doi.org/10.3390/ma14071614 - 26 Mar 2021

Cited by 5 | Viewed by 1692

Abstract

The goal of current research was to investigate the influence of adding low shrinkage “Phene” like comonomers hexaethylene glycol bis(carbamate-isoproply-α-methylstyrene) (HE-Phene) and triethylene glycol bis(carbamate-isoproply-α-methylstyrene) (TE-Phene) on the surface and color characteristics of composite resin. A range of weight fractions (0, 10, 20, [...] Read more.

The goal of current research was to investigate the influence of adding low shrinkage “Phene” like comonomers hexaethylene glycol bis(carbamate-isoproply-α-methylstyrene) (HE-Phene) and triethylene glycol bis(carbamate-isoproply-α-methylstyrene) (TE-Phene) on the surface and color characteristics of composite resin. A range of weight fractions (0, 10, 20, 30, 40 wt.%) of HE/TE-Phene monomers were mixed with bisphenol A glycidyl methacrylate (GMA)/triethylene glycol dimethacrylate (TEGDMA) monomer. Experimental composite resins were made by mixing 71 wt.% of silica fillers to 29 wt.% of the resin matrix. A Vickers indenter and glossmeter were used for testing surface hardness (SH) and gloss (SG) at 60°. A chewing-simulator was used to evaluate the surface wear after 15,000 cycles. Color change (∆E) and translucency parameter (TP) were measured using a spectrophotometer. Data showed that HE/TE-Phene monomer had no negative impact (p > 0.05) on surface gloss, wear, color change and translucency of experimental composite resins. Surface hardness was in a reducing direction with the increas in HE/TE-Phene weight fraction (p < 0.05). The study results suggested that incorporating HE/TE-Phene monomers up to 30 wt.% with Bis-GMA/TEGDMA resin did not negatively influence the surface integrity of composite resins except for SH. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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17 pages, 4451 KiB

Open AccessArticle

Impact of Fast High-Intensity versus Conventional Light-Curing Protocol on Selected Properties of Dental Composites

by Sufyan Garoushi, Lippo Lassila and Pekka K. Vallittu

Materials 2021, 14(6), 1381; https://doi.org/10.3390/ma14061381 - 12 Mar 2021

Cited by 22 | Viewed by 2852

Abstract

To study the influence of fast high-intensity (3-s) and conventional (20-s) light curing protocols on certain physical properties including light-transmission and surface wear of two nano-hybrid composite resins (Tetric PowerFill and Essentia U) specifically designed for both curing protocols. According to ISO standards, [...] Read more.

To study the influence of fast high-intensity (3-s) and conventional (20-s) light curing protocols on certain physical properties including light-transmission and surface wear of two nano-hybrid composite resins (Tetric PowerFill and Essentia U) specifically designed for both curing protocols. According to ISO standards, the following properties were investigated: flexural properties, fracture toughness and water sorption/solubility. FTIR-spectrometry was used to calculate the double bond conversion (DC%). A wear test using a chewing simulator was performed with 15,000 chewing cycles. A tensilometer was used to measure the shrinkage stress. Light transmission through various thicknesses (1, 2, 3 and 4 mm) of composite resins was quantified. The Vickers indenter was utilized for evaluating surface microhardness (VH) at the top and the bottom sides. Scanning electron microscopy was utilized to investigate the microstructure of each composite resin. The light curing protocol did not show a significant (p > 0.05) effect on the mechanical properties of tested composite resins and differences were material-dependent. Shrinkage stress, DC% and VH of both composite resins significantly increased with the conventional 20 s light curing protocol (p < 0.05). Light curing conventional composite resin with the fast high-intensity (3-s) curing protocol resulted in inferior results for some important material properties. Full article

(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)

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