Advanced Polymeric Composites in Dentistry: Synthesis, Properties, and Applications

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 77485

Special Issue Editors


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Guest Editor
Turku Clinical Biomaterial Center, University of Turku, Turku, Finland
Interests: dental composite materials, FRCs (fiber reinforced composites), mechanical properties

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Guest Editor
Department of Biomaterials Science and Turku Clinical Biomaterials Center—TCBC, Institute of Dentistry, University of Turku, Turku, Finland
Interests: fiber reinforced composites; dental materials
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Biomaterials Science, Institute of Dentistry and BioCity Turku Biomaterial Research Program, University of Turku, Turku 20520, Finland
Interests: fiber reinforeced composites; biomechanics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The polymeric materials has been used in dentistry for decades. Due to easthetic demands they have lately become even more popular. Unfortunately, the mechanical properties, handling, and need for chair-side curing of these composite restorations leave a lot of space for improvement, particularly in terms of mechanical properties, polymerization shrinkage and polymerization-induced stress, fracture, abrasion and wear resistance, marginal leakage, discoloration, and biocompatbility. These limitaions shorten the lifespan of a composite restoration and are the driving force behind advancements in dental composites. Attempts have been made to modify the monomer matrix or filler technology in oreder to improve overall properties of dental composits. One of these attemps is by using fibre-reinforced composites (FRCs). Fibres are used to improve the durability of composites by enhancing the toughness, which is a key property; having direct correlation with clinical success of composite restorations. Several parameters, including the fibre volume fraction and fibre direction, have a substantial impact on the mechanical properties of FRCs which can be anisotropic, orthotropic, or isotropic. The fibres can vary in composition (carbon, polyamide, polyethylene, and glass) and form (long or short), depending on the final application of the material. Short fibres are typically used to reinforce restorative materials, while long fibres increase the mechanical properties of dental appliances used at application requiring high mechanical properties. Since FRCs are used in various fields (restorative dentistry, prosthodontics, orthodontics, periodontology, etc.), the requirements set for materials also vary greatly. Not only the fibres but also the resin/polymer matrix, particulate fillers, and particularly the surface treatment of fibres and fillers affect the final properties of the FRCs.

Contemporary restorative dentistry uses direct or indirect bilayered restorations to restore lost tooth tissue with biomimetics as the new driving force. From a biomimetic point of view, the use of short FRC as dentin-replacing material appears to be a promising treatment strategy and may solve some potential problems associated with conventional composite restoration in high stress-bearing areas.

Based on such factors, this Special Issue is intended to cover the topic of polymeric composites, like FRCs, in dentistry from various perspectives; synthesis, properties and applications. Researchers, scientists, and clinicans are encouraged to contribute original research papers, clinical trials or reports, reviews, and meta-analyses that will promote the continuation of fiber reinforcement technology in dentistry.

Potential topics of this Special Issue include but are not limited to the following:

  • Resin synthesis
  • Physical and mechanical properties
  • Composite processing
  • Polymer–fibre interphase/fibre sizing
  • Biomimetic restoration
  • Clinical applications and requirements

Dr. Eija Säilynoja
Dr. Sufyan Garoushi
Dr. Lippo Lassila
Guest Editors

Keywords

  • polymeric composite
  • fibre-reinforced composite (FRC)
  • synthesis
  • mechanical properties
  • reinforcement
  • dental application
  • clinical success
  • restoration durability

Published Papers (29 papers)

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9 pages, 1701 KiB  
Article
Influence of New Sleeve Composite on Fracture Behavior of Anterior Teeth with Flared Root Canals
by Shinji Yoshii, Sufyan Garoushi, Chiaki Kitamura, Pekka K. Vallittu and Lippo Lassila
Polymers 2022, 14(19), 4073; https://doi.org/10.3390/polym14194073 - 28 Sep 2022
Viewed by 1194
Abstract
We evaluated the fracture strength and failure mode of non-ferrule teeth with flared root canals that were restored using new experimental sleeve composites. Fifty endodontically treated anterior teeth with flared root canals were restored with direct restorations utilizing different techniques. Group A had [...] Read more.
We evaluated the fracture strength and failure mode of non-ferrule teeth with flared root canals that were restored using new experimental sleeve composites. Fifty endodontically treated anterior teeth with flared root canals were restored with direct restorations utilizing different techniques. Group A had teeth (non-ferrule) restored using commercialized MI glass fiber post + Gradia Core as core build-up. Group B had teeth (non-ferrule) restored with commercialized i-TFC glass fiber post + sleeve system. In Group C, the teeth (non-ferrule) were restored with an experimental sleeve composite with commercialized MI glass fiber post and Gradia Core. Group D, teeth (non-ferrule), were restored using custom-made tapered E-glass filling post and Gradia Core. Group E, teeth (with ferrule), were restored with commercialized MI glass fiber post + Gradia Core. After core construction, all specimens underwent direct composite crown restoration and were loaded until fracture using a universal testing machine. Average fracture loads were compared, and the failure modes were observed. Group C exhibited significantly greater fracture strength than other groups (p < 0.05). Favorable fracture teeth ratio of group C was more than that of the other groups. Thus, the new experimental sleeve composite could be clinically useful for core construction of non-ferrule teeth. Full article
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11 pages, 4295 KiB  
Article
DEAE-Dextran Coated AgNPs: A Highly Blendable Nanofiller Enhances Compressive Strength of Dental Resin Composites
by Shabia Azhar, Nosheen Fatima Rana, Amer Sohail Kashif, Tahreem Tanweer, Iqra Shafique and Farid Menaa
Polymers 2022, 14(15), 3143; https://doi.org/10.3390/polym14153143 - 2 Aug 2022
Cited by 9 | Viewed by 1858
Abstract
Micro-crack formation and resultant bacterial infiltration are major causes of secondary caries formation in dental resin-based composite restorations. Improving dental resin composites’ mechanical and biological properties using highly bendable nanoparticles (NPs) can resolve this issue. This study aims to develop novel Diethylaminoethyl (DEAE)-Dextran [...] Read more.
Micro-crack formation and resultant bacterial infiltration are major causes of secondary caries formation in dental resin-based composite restorations. Improving dental resin composites’ mechanical and biological properties using highly bendable nanoparticles (NPs) can resolve this issue. This study aims to develop novel Diethylaminoethyl (DEAE)-Dextran silver nanoparticles (AgNPs) and subsequently modify composite resins with these NPs to enhance their mechanical and antibacterial properties. DEAE-Dextran AgNPs were successfully synthesized using a chemical reduction method that was confirmed with the help of ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Zeta potential, and energy-dispersive X-ray spectroscopy (EDS). Antibacterial activity of a composite disc with DEAE-Dextran AgNPs was tested against Streptococcus mutans, Enterococcus faecalis, and oral microcosm. The composite discs prepared with DEAE-Dextran AgNPs exhibited excellent antibacterial activity compared with composite resin reinforced by simple AgNPs (p < 0.05). Mechanical properties were significantly enhanced by adding DEAE-Dextran into composite resin (p < 0.05). Moreover, unlike AgNPs, DEAE-Dextran AgNPs were found to be less hemolytic. The results establish strong ground applications for DEAE-Dextran-modified dental composite resins in restorative dental applications. Full article
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15 pages, 3738 KiB  
Article
The Microhardness and Surface Roughness Assessment of Bulk-Fill Resin Composites Treated with and without the Application of an Oxygen-Inhibited Layer and a Polishing System: An In Vitro Study
by Ann Carrillo-Marcos, Giuliany Salazar-Correa, Leonor Castro-Ramirez, Marysela Ladera-Castañeda, Carlos López-Gurreonero, Hernán Cachay-Criado, Ana Aliaga-Mariñas, Alberto Cornejo-Pinto, Luis Cervantes-Ganoza and César Félix Cayo-Rojas
Polymers 2022, 14(15), 3053; https://doi.org/10.3390/polym14153053 - 28 Jul 2022
Cited by 13 | Viewed by 2337
Abstract
The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks [...] Read more.
The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal–Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved. Full article
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16 pages, 4426 KiB  
Article
Human Enamel Fluorination Enhancement by Photodynamic Laser Treatment
by Corina Elena Tisler, Marioara Moldovan, Ioan Petean, Smaranda Dana Buduru, Doina Prodan, Codruta Sarosi, Daniel-Corneliu Leucuţa, Radu Chifor, Mîndra Eugenia Badea and Razvan Ene
Polymers 2022, 14(14), 2969; https://doi.org/10.3390/polym14142969 - 21 Jul 2022
Cited by 7 | Viewed by 1544
Abstract
Poor oral hygiene leads to serious damages of theteeth’s surface enamel such as micro-abrasions and acid erosion. These alterations combined with bacterial plaque result in cavity appearance. Prophylactic measures include various techniques for enamel surface restoration. Fluorination is one of the most important [...] Read more.
Poor oral hygiene leads to serious damages of theteeth’s surface enamel such as micro-abrasions and acid erosion. These alterations combined with bacterial plaque result in cavity appearance. Prophylactic measures include various techniques for enamel surface restoration. Fluorination is one of the most important treatments for this purpose. Therefore, in the present research, we investigated the classical fluorination treatment compared with laser photodynamic fluorination performed on human enamel samples with poor surface quality. Three sample groups were investigated: veneer (F), inlay (I), and crowns (C). The general morphologic aspect was investigated by scanning electron microscopy (SEM), and the specific details such as the fine microstructure and nanostructure were investigated by atomic force microscopy (AFM) of the surface roughness. The samples were also investigated by Fourier transformed infrared attenuated total reflectance (FTIR-ATR) to evidence the fluorination effect on the enamel surface. Results showed that all initial samples had an altered state with micro-abrasions and erosion with mineral loss, which increase the surface roughness. The F group was the most damaged, having a higher roughness, and the I group was less damaged. Classic fluorination treatment partially restored the enamel by local re-mineralization, but did not obtain the parameters of healthy enamel. However, a significant decrease of the roughness was observed (statistical relevance p = 0.001 with the Breusch–Pagan Test). This fact was supported by the presence of newly formed fluorides in the FTIR-ATR spectra. The photodynamic laser fluorination restores the enamel in an enhanced manner by a strong re-mineralization, which implies a significant roughness value decrease comparable to healthy enamel. The Breusch–Pagan Test confirmed the relevance with p = 0.001. This is due to an extended re-mineralization abundant in fluoride crystals as observed by AFM and FTIR. Statistical p-values regarding laser application were in the range of 0.02–0.06, supporting its relevance in the fluorination effect. The final conclusion is that the photodynamic effect is able to favor the newly formed fluoride deposition onto the affected sites of the enamel surface. Full article
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8 pages, 879 KiB  
Communication
Fracture Resistance of Anterior Crowns Reinforced by Short-Fiber Composite
by Lippo Lassila, Anssi Haapsaari, Pekka K. Vallittu and Sufyan Garoushi
Polymers 2022, 14(9), 1809; https://doi.org/10.3390/polym14091809 - 28 Apr 2022
Cited by 3 | Viewed by 1492
Abstract
The aim of this study was to investigate the load-bearing capacity of anterior crowns made of different commercial particulate-filled composites (PFCs) and reinforced by a core of short-fiber composite (SFC) (bilayer structure). Four groups of composite crowns were fabricated for an upper central [...] Read more.
The aim of this study was to investigate the load-bearing capacity of anterior crowns made of different commercial particulate-filled composites (PFCs) and reinforced by a core of short-fiber composite (SFC) (bilayer structure). Four groups of composite crowns were fabricated for an upper central incisor (n = 20/group). Two groups were made of chair-side PFC composites (G-aenial anterior, GC, Japan and Denfil, Vericom, Korea) with or without SFC-core (everX Flow, GC). One group was made of laboratory PFC composite (Gradia Plus, GC) with or without SFC-core. The last group was made of plain SFC composite polymerized with a hand-light curing unit only or further polymerized in a light-curing oven. Using a universal-testing device, crown restorations were statically loaded until they fractured, and failure modes were visually investigated. Analysis of variance (p = 0.05) was used to evaluate the data, followed by Tukey’s post hoc test. Bilayer structure crowns with SFC-core and surface PFC gave superior load-bearing capacity values compared to those made of monolayer PFC composites; however, significant differences (p < 0.05) were found in the chair-side composite groups. Additional polymerization has no impact on the load-bearing capacity values of SFC crowns. Using SFC as a core material with PFC veneering composite to strengthen anterior crown restorations proved to be a promising strategy for further testing. Full article
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16 pages, 17581 KiB  
Article
Improved Mechanical Properties and Bioactivity of Silicate Based Bioceramics Reinforced Poly(ether-ether-ketone) Nanocomposites for Prosthetic Dental Implantology
by Noha Taymour, Amal E. Fahmy, Mohamed Abdel Hady Gepreel, Sherif Kandil and Ahmed Abd El-Fattah
Polymers 2022, 14(8), 1632; https://doi.org/10.3390/polym14081632 - 18 Apr 2022
Cited by 12 | Viewed by 2654
Abstract
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant [...] Read more.
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant applications. In this work, nanocomposites based on PEEK reinforced with bioactive silicate-based bioceramics (forsterite or bioglass) as nanofillers were prepared using high energy ball milling followed by melt blending and compression molding. The influence of nanofillers type and content (10, 20 and 30 wt.%) on the crystalline structure, morphology, surface roughness, hydrophilicity, microhardness, elastic compression modulus, and flexural strength of the nanocomposites was investigated. The scanning electron microscopy images of the nanocomposites with low nanofillers content showed a homogenous surface with uniform dispersion within the PEEK matrix with no agglomerates. All nanocomposites showed an increased surface roughness compared to pristine PEEK. It was found that the incorporation of 20 wt.% forsterite was the most effective in the nanocomposite formulation compared with bioglass-based nanocomposites; it has significantly improved the elastic modulus, flexural strength, and microhardness. In vitro bioactivity evaluation, which used biomimetic simulated body fluid indicated the ability of PEEK nanocomposites loaded with forsterite or bioglass nanofillers to precipitate calcium and phosphate bone minerals on its surface. These nanocomposites are expected to be used in long-term load-bearing implant applications and could be recommended as a promising alternative to titanium and zirconia when used as a dental implant material. Full article
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15 pages, 4954 KiB  
Article
Effect of Different Solutions on the Colour Stability of Nanoparticles or Fibre Reinforced PMMA
by Abdulaziz Alhotan, Alaaeldin Elraggal, Julian Yates, Julfikar Haider, Carlos Alberto Jurado and Nikolaos Silikas
Polymers 2022, 14(8), 1521; https://doi.org/10.3390/polym14081521 - 8 Apr 2022
Cited by 9 | Viewed by 1956
Abstract
This study aimed to evaluate the colour stability of polymethyl methacrylate (PMMA) denture base reinforced with ZrO2 nanoparticles, E-glass fibres, and TiO2 nanoparticles at various concentrations over 180-day storage in Steradent™ (STD) denture cleaner or coffee (CF). A total of 130 [...] Read more.
This study aimed to evaluate the colour stability of polymethyl methacrylate (PMMA) denture base reinforced with ZrO2 nanoparticles, E-glass fibres, and TiO2 nanoparticles at various concentrations over 180-day storage in Steradent™ (STD) denture cleaner or coffee (CF). A total of 130 disc-shaped specimens were fabricated at various filler concentrations and divided into four main groups to measure the colour changes. Groups Z, T, and E consisted of PMMA reinforced with ZrO2 nanoparticles, TiO2 nanoparticles, or E-glass fibre, respectively, while Group C consisted of PMMA specimens without filler served as the control group (n = 10). The three reinforced groups were further subdivided according to the filler content (n = 10) added to the PMMA (1.5%, 3.0%, 5.0%, and 7.0% wt.%). Half of the specimens were stored in STD, while the other half was stored in CF for 180 days. A Minolta Chroma Meter was used to measure the colour changes (ΔE) at 7, 30, 90 and then 180 days. The results were assessed using two-way repeated-measures analysis of variance (RM-ANOVA) along with Bonferroni post hoc tests at a p ≤ 0.05 significance level. Significant different colour changes (ΔΕ) were observed between all tested groups and across different time points. TiO2-reinforced PMMA in STD/CF showed the lowest colour stability, while the E-glass fibre-reinforced PMMA in STD/CF showed the highest colour stability. Furthermore, coffee appeared to have the greatest impact on the colour change in comparison to the SteradentTM. The results indicated that the filler type and concentration, type of solution, and length of storage all affected the colour stability of the tested specimens. Full article
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12 pages, 3041 KiB  
Article
Effect of Light Curing Distance on Microhardness Profiles of Bulk-Fill Resin Composites
by Fatin A. Hasanain, Hani M. Nassar and Reem A. Ajaj
Polymers 2022, 14(3), 528; https://doi.org/10.3390/polym14030528 - 28 Jan 2022
Cited by 11 | Viewed by 2984
Abstract
Bulk-fill (BF) dental resin composites are made to be polymerized in increments of up to 5 mm rather than the 2 mm increment recommended for conventional composites. This project aimed to determine microhardness (MH) profiles of BF resin composites at different depths and [...] Read more.
Bulk-fill (BF) dental resin composites are made to be polymerized in increments of up to 5 mm rather than the 2 mm increment recommended for conventional composites. This project aimed to determine microhardness (MH) profiles of BF resin composites at different depths and varying light cure (LC) distances from the light source in an attempt to mimic varying clinical situations. Forty-eight cylindrical specimens (4 mm diameter and 6 mm height) were prepared from 3 BF composites: Tetric N-Ceram Bulk-Fill (TBF), Filtek One Bulk-Fill (FBF), and Sonic-Fill 2 (SF2). Four different distances (0, 2, 4, and 6 mm) from the LC unit were investigated. Vickers MH was measured at the top and bottom of the samples and at every 1 mm, by creating 3 indentations at each depth. The bottom-top microhardness ratio (MHR) and percentage reduction in MHR were also measured. Data was analyzed using mixed-model repeated-measure ANOVA at 0.05 significance level. The main variables effects “material, LC distance, and depth” were significant (p < 0.001). Increasing LC distance and the depth of the tested BF significantly affected Vickers MH and MHR. None of the tested BF materials had sufficient MHR at the depths of 4–6 mm. SF2 showed the least MHR reduction. Full article
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16 pages, 2854 KiB  
Article
Investigation of the Damping Capabilities of Different Resin-Based CAD/CAM Restorative Materials
by Thomas Niem, Stefan Gonschorek and Bernd Wöstmann
Polymers 2022, 14(3), 493; https://doi.org/10.3390/polym14030493 - 26 Jan 2022
Cited by 2 | Viewed by 2167
Abstract
The aim of the present study was to evaluate and quantify the damping properties of common resin-based computer-aided design and computer-aided manufacturing (CAD/CAM) restorative materials (CRMs) and assess their energy dissipation abilities. Leeb hardness (HLD), together with its deduced energy dissipation [...] Read more.
The aim of the present study was to evaluate and quantify the damping properties of common resin-based computer-aided design and computer-aided manufacturing (CAD/CAM) restorative materials (CRMs) and assess their energy dissipation abilities. Leeb hardness (HLD), together with its deduced energy dissipation data (HLDdis), and loss tangent values recorded via dynamic mechanical analysis (DMA) were determined for six polymer, four composite, and one ceramic CRM as well as one metal. Data were statistically analyzed. Among resin-based CRMs, the significantly highest HLDdis data were detected for the fiber-reinforced composite FD (p < 0.001) directly followed by the filler-reinforced Ambarino High Class (p < 0.001). The significantly lowest HLDdis values were observed for the polymer-based CRM Telio CAD (p < 0.001). For loss tangent, both PEEK materials showed the significantly lowest data and the polymer-based M-PM the highest results with all composite CRMs in between. HLDdis data, which simultaneously record the energy dissipation mechanism of plastic material deformation, more precisely characterize the damping behavior of resin-based CRMs compared to loss tangent results that merely describe viscoelastic material behavior. Depending on material composition, resin-based CRMs reveal extremely different ratios of viscoelastic damping but frequently show enhanced HLDdis values because of plastic material deformation. Future developments in CAD/CAM restorative technology should focus on developing improved viscoelastic damping effects. Full article
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14 pages, 656 KiB  
Article
Bisphenol A Release from Dental Composites and Resin-Modified Glass Ionomers under Two Polymerization Conditions
by Antonin Tichy, Marketa Simkova, Radka Vrbova, Adela Roubickova, Michaela Duskova and Pavel Bradna
Polymers 2022, 14(1), 46; https://doi.org/10.3390/polym14010046 - 23 Dec 2021
Cited by 10 | Viewed by 3162
Abstract
Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing [...] Read more.
Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing BPA-based monomers, two “BPA-free” composites, and two RM-GICs were polymerized from one side for 20 s at 1300 mW/cm2 or for 5 s at 3000 mW/cm2. The amounts of BPA released in artificial saliva and methanol after 1, 4, 9, 16, 35, 65, 130, and 260 days were measured using liquid chromatography–tandem mass spectrometry. The highest amounts of BPA were released from conventional composites, followed by RM-GICs, while the least was released from “BPA-free” composites. Amounts of released BPA were significantly higher in methanol and decreased gradually after the first day. Fast polymerization (5 s at 3000 mW/cm2) resulted in a significantly higher release of BPA after 1 day, but the effect of polymerization conditions was not significant overall. In conclusion, fast polymerization increased the initial release of BPA, but the released amounts were significantly lower than the current tolerable daily intake (4 μg/kg body weight/day) even in methanol, representing the worst-case scenario of BPA release. Full article
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12 pages, 3059 KiB  
Article
Novel Polymerization of Dental Composites Using Near-Infrared-Induced Internal Upconversion Blue Luminescence
by Shu-Fen Chuang, Chu-Chun Liao, Jui-Che Lin, Yu-Cheng Chou, Tsung-Lin Lee and Ting-Wen Lai
Polymers 2021, 13(24), 4304; https://doi.org/10.3390/polym13244304 - 9 Dec 2021
Cited by 2 | Viewed by 2789
Abstract
Blue light (BL) curing on dental resin composites results in gradient polymerization. By incorporating upconversion phosphors (UP) in resin composites, near-infrared (NIR) irradiation may activate internal blue emission and a polymerization reaction. This study was aimed to evaluate the competency of the NIR-to-BL [...] Read more.
Blue light (BL) curing on dental resin composites results in gradient polymerization. By incorporating upconversion phosphors (UP) in resin composites, near-infrared (NIR) irradiation may activate internal blue emission and a polymerization reaction. This study was aimed to evaluate the competency of the NIR-to-BL upconversion luminance in polymerizing dental composites and to assess the appropriate UP content and curing protocol. NaYF4 (Yb3+/Tm3+ co-doped) powder exhibiting 476-nm blue emission under 980-nm NIR was adapted and ball-milled for 4–8 h to obtain different particles. The bare particles were assessed for their emission intensities, and also added into a base composite Z100 (3M EPSE) to evaluate their ability in enhancing polymerization under NIR irradiation. Experimental composites were prepared by dispensing the selected powder and Z100 at different ratios (0, 5, 10 wt% UP). These composites were irradiated under different protocols (BL, NIR, or their combinations), and the microhardness at the irradiated surface and different depths were determined. The results showed that unground UP (d50 = 1.9 μm) exhibited the highest luminescence, while the incorporation of 0.4-μm particles obtained the highest microhardness. The combined 20-s BL and 20–120-s NIR significantly increased the microhardness on the surface and internal depths compared to BL correspondents. The 5% UP effectively enhanced the microhardness under 80-s NIR irradiation but was surpassed by 10% UP with longer NIR irradiation. The combined BL-NIR curing could be an effective approach to polymerize dental composites, while the intensity of upconversion luminescence was related to specific UP particle size and content. Incorporation of 5–10% UP facilitates NIR upconversion polymerization on dental composites. Full article
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10 pages, 2877 KiB  
Article
Surface Properties of Polymer Resins Fabricated with Subtractive and Additive Manufacturing Techniques
by Amal S. Al-Qahtani, Huda I. Tulbah, Mashael Binhasan, Maria S. Abbasi, Naseer Ahmed, Sara Shabib, Imran Farooq, Nada Aldahian, Sidra S. Nisar, Syeda A. Tanveer, Fahim Vohra and Tariq Abduljabbar
Polymers 2021, 13(23), 4077; https://doi.org/10.3390/polym13234077 - 24 Nov 2021
Cited by 23 | Viewed by 2822
Abstract
This study aimed to compare the surface roughness, hardness, and flexure strength of interim indirect resin restorations fabricated with CAD-CAM (CC), 3D printing (3D), and conventional techniques (CV). Twenty disk (3 mm × Ø10 mm) and ten bar specimens (25 × 2 × [...] Read more.
This study aimed to compare the surface roughness, hardness, and flexure strength of interim indirect resin restorations fabricated with CAD-CAM (CC), 3D printing (3D), and conventional techniques (CV). Twenty disk (3 mm × Ø10 mm) and ten bar specimens (25 × 2 × 2 mm) were fabricated for the CC, 3D, and CV groups, to be used for surface roughness, micro-hardness, and flexural strength testing using standardized protocol. Three indentations for Vickers micro-hardness (VHN) were performed on each disk and an average was identified for each specimen. Surface micro-roughness (Ra) was calculated in micrometers (μm) using a 3D optical non-contact surface microscope. A three-point bending test with a universal testing machine was utilized for assessing flexural strength. The load was applied at a crosshead speed of 3 mm/min over a distance of 25 mm until fracture. Means and standard deviations were compared using ANOVA and post hoc Tukey–Kramer tests, and a p-value of ≤0.05 was considered statistically significant. Ra was significantly different among the study groups (p < 0.05). Surface roughness among the CC and CV groups was statistically comparable (p > 0.05). However, 3D showed significantly higher Ra compared to CC and CV samples (p < 0.05). Micro-hardness was significantly higher in 3D samples (p < 0.05) compared to CC and CV specimens. In addition, CC and CV showed comparable micro-hardness (p > 0.05). A significant difference in flexural strength was observed among the study groups (p < 0.05). CC and 3D showed comparable strength outcomes (p > 0.05), although CV specimens showed significantly lower (p < 0.05) strength compared to CC and 3D samples. The 3D-printed provisional restorative resins showed flexural strength and micro-hardness comparable to CAD-CAM fabricated specimens, and surface micro-roughness for printed specimens was considerably higher compared to CAD-CAM and conventional fabrication techniques. Full article
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8 pages, 2227 KiB  
Article
Effect of Multiple Enamel Surface Treatments on Micro-Shear Bond Strength
by René Daher, Ivo Krejci, Mustapha Mekki, Charlotte Marin, Enrico Di Bella and Stefano Ardu
Polymers 2021, 13(20), 3589; https://doi.org/10.3390/polym13203589 - 18 Oct 2021
Cited by 5 | Viewed by 1747
Abstract
Objectives: The aim of this study was to evaluate the effect of different enamel surface treatments on the micro-shear bond strength. Materials and methods: Sixty-four approximal surfaces from freshly extracted molars were randomly assigned to eight groups, according to combinations of [...] Read more.
Objectives: The aim of this study was to evaluate the effect of different enamel surface treatments on the micro-shear bond strength. Materials and methods: Sixty-four approximal surfaces from freshly extracted molars were randomly assigned to eight groups, according to combinations of the following enamel surface treatments: ground or unground, 37.5% phosphoric acid etching time of 15 or 30 s, and with or without primer application. The same bonding agent (Optibond FL™ Adhesive, Kerr) was then used for all groups, and a 1.8 mm diameter resin composite (Harmonize™, Kerr) cylinder was built up on the bonded surface. Samples underwent a shear force test at a crosshead speed of 1 mm/min until failure. Bond strength was calculated, and failure modes were inspected under an optical microscope. Results: Bond-strength values ranged from 8.2 MPa for 15 s etched unground enamel with primer application to 19.6 MPa for 30 s etched ground enamel without primer application. ANOVA and Fisher’s LSD post hoc tests revealed significant differences between the groups. Conclusions: Etching time and grinding have a statistically significant effect on the micro-shear bond strength of a three-step etch-and-rinse adhesive system on enamel. Primer application does not seem to be beneficial for enamel adhesion. Full article
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16 pages, 1974 KiB  
Article
Investigating a Commercial Functional Adhesive with 12-MDPB and Reactive Filler to Strengthen the Adhesive Interface in Eroded Dentin
by Madalena Belmar da Costa, António HS Delgado, Tomás Amorim Afonso, Luís Proença, Ana Sofia Ramos and Ana Mano Azul
Polymers 2021, 13(20), 3562; https://doi.org/10.3390/polym13203562 - 15 Oct 2021
Cited by 3 | Viewed by 1644
Abstract
To compare the adhesive interface of eroded dentin formed by a functional dental adhesive and a gold standard strategy, by testing microtensile bond strength (μTBS), hardness/elastic modulus. Permanent sound human molars were randomly allocated to four experimental groups, all subject to artificial erosion [...] Read more.
To compare the adhesive interface of eroded dentin formed by a functional dental adhesive and a gold standard strategy, by testing microtensile bond strength (μTBS), hardness/elastic modulus. Permanent sound human molars were randomly allocated to four experimental groups, all subject to artificial erosion (0.05 M citric acid; 3× daily, 5 days). Groups included control Clearfil SE Bond 2 (CFSE), and experimental group Clearfil SE Protect (CFP), at two different time points-immediate (24 h) and long term (3 months–3 M). Samples were sectioned into microspecimens for μTBS (n = 8) and into 2-mm thick slabs for nanoindentation assays (n = 3). Groups CFSE_3M and CFP_3M were stored in artificial saliva. Statistical analysis included two-way ANOVA for μTBS data, while hardness/modulus results were analyzed using Kruskal–Wallis H Test (significance level of 5%; SPSS v.27.0). Although no significant differences were found between mean μTBS values, for different adhesives and time points (p > 0.05), a positive trend, with μTBS rising in the CFP_3M group, was observed. Regarding hardness, no significant differences were seen in the hybrid layer, considering the two variables (p > 0.05), while the reduced elastic modulus rose in CFP_3M when compared to 24 h. Thus, CFP shows similar mechanical and adhesive performance to CFSE in eroded dentin, although it may comprise promising long-term results. This is advantageous in eroded substrates due to their increased enzymatic activity and need for remineralization. Full article
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15 pages, 4890 KiB  
Article
CAD/CAM Resin-Based Composites for Use in Long-Term Temporary Fixed Dental Prostheses
by Franziska Hensel, Andreas Koenig, Hans-Martin Doerfler, Florian Fuchs, Martin Rosentritt and Sebastian Hahnel
Polymers 2021, 13(20), 3469; https://doi.org/10.3390/polym13203469 - 9 Oct 2021
Cited by 18 | Viewed by 3326
Abstract
The aim of this in vitro study was to analyse the performance of CAD/CAM resin-based composites for the fabrication of long-term temporary fixed dental prostheses (FDP) and to compare it to other commercially available alternative materials regarding its long-term stability. Four CAD/CAM materials [...] Read more.
The aim of this in vitro study was to analyse the performance of CAD/CAM resin-based composites for the fabrication of long-term temporary fixed dental prostheses (FDP) and to compare it to other commercially available alternative materials regarding its long-term stability. Four CAD/CAM materials [Structur CAD (SC), VITA CAD-Temp (CT), Grandio disc (GD), and Lava Esthetic (LE)] and two direct RBCs [(Structur 3 (S3) and LuxaCrown (LC)] were used to fabricate three-unit FDPs. 10/20 FDPs were subjected to thermal cycling and mechanical loading by chewing simulation and 10/20 FDPs were stored in distilled water. Two FDPs of each material were forwarded to additional image diagnostics prior and after chewing simulation. Fracture loads were measured and data were statistically analysed. SC is suitable for use as a long-term temporary (two years) three-unit FDP. In comparison to CT, SC featured significantly higher breaking forces (SC > 800 N; CT < 600 N) and the surface wear of the antagonists was (significantly) lower and the abrasion of the FDP was similar. The high breaking forces (1100–1327 N) of GD and the small difference compared to LE regarding flexural strength showed that the material might be used for the fabrication of three-unit FDPs. With the exception of S3, all analysed direct or indirect materials are suitable for the fabrication of temporary FDPs. Full article
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12 pages, 3121 KiB  
Article
Effect of Interpenetrating Polymer Network (IPN) Thermoplastic Resin on Flexural Strength of Fibre-Reinforced Composite and the Penetration of Bonding Resin into Semi-IPN FRC Post
by Minori Hatta, Akikazu Shinya, Harunori Gomi, Pekka K. Vallittu, Eija Säilynoja and Lippo V. J. Lassila
Polymers 2021, 13(18), 3200; https://doi.org/10.3390/polym13183200 - 21 Sep 2021
Cited by 7 | Viewed by 2587
Abstract
The purpose of this study was to evaluate the effects of interpenetrating polymer network (IPN) thermoplastic resin on the flexural strength of fibre-reinforced composite (FRC) with different IPN polymer compositions. The penetration of bonding resin into semi-IPN FRC posts was also evaluated. The [...] Read more.
The purpose of this study was to evaluate the effects of interpenetrating polymer network (IPN) thermoplastic resin on the flexural strength of fibre-reinforced composite (FRC) with different IPN polymer compositions. The penetration of bonding resin into semi-IPN FRC posts was also evaluated. The IPN thermoplastic resin used was UDMA-MMA monomer with either PMMA (0.5%, 2%, 5%) or PMMA-copolymer (0.5%, 2%). A no added IPN polymer resin was also made. Mixed resin was impregnated to S- and E-glass fibre rovings. These resins and resin impregnated fibres were used for flexural strength (FS) test. To evaluate the penetration of bonding resin into semi-IPN post, SEM observation was done with various impregnation time and polymerization mehods (hand-light- and oven-cure). The result of FS was recorded from 111.7 MPa (no-IPN polymer/no-fibre-reinforcement) to 543.0 MPa (5% PMMA/S-glass FRC). ANOVA showed that there were significant differences between fibre-reinforcement and no-fibre-reinforcement (p < 0.01) both in S- and E-glass fibre groups, and between 0.5% PMMA and 5% PMMA in the S-glass FRC group. SEM micrographs showed that the penetration layers of bonding resin into hand-light cured semi-IPN posts were different according to impregnation time. Fibre reinforcement is effective to improve flexural strength. The depth of penetration layer of bonding resin into semi-IPN matrix resin was improved when a hand-light cure was used. Full article
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9 pages, 11696 KiB  
Article
Polymerization Shrinkage of Short Fiber Reinforced Dental Composite Using a Confocal Laser Analysis
by Daisuke Miura, Yoshiki Ishida and Akikazu Shinya
Polymers 2021, 13(18), 3088; https://doi.org/10.3390/polym13183088 - 13 Sep 2021
Cited by 6 | Viewed by 2814
Abstract
The purpose of this study was to investigate the polymerization shrinkage of short fiber reinforced composite (SFRC) using a multicolor confocal displacement laser that can measure the polymerization shrinkage with high accuracy. The three types of SFRCs used in this study were XD [...] Read more.
The purpose of this study was to investigate the polymerization shrinkage of short fiber reinforced composite (SFRC) using a multicolor confocal displacement laser that can measure the polymerization shrinkage with high accuracy. The three types of SFRCs used in this study were XD (Ever X Flow Dentin), XB (Ever X Flow Bulk), and XP (EverX Posterior). In addition, CF (Clearfil majesty ES Flow) with hybrid type filler was used as a control. The measured values of the final polymerization shrinkage rate and amount of polymerization shrinkage rate when the polymerization shrinkage rate became constant (less than 0.1 µm/s) were approximated for all SFRCs. XP had a large aspect ratio of glass fiber filler and showed a significant difference from XD with a small aspect ratio (p < 0.05). There was no significant difference in the measured value of time when the polymerization contraction reached a constant speed (0.1 µm/s or less) for all SFRCs (p > 0.05). There was no significant difference in the measured values of polymerization shrinkage rate after the polymerization shrinkage reached a constant rate for all SFRCs (p > 0.05). These results show that glass fiber with large aspect ratio can alleviate polymerization shrinkage stress. The polymerization behavior of SFRC was found to be dependent on the amount of glass fiber filler, aspect ratio, and orientation. Full article
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12 pages, 2896 KiB  
Article
Application of β-Tricalcium Phosphate in Adhesive Dentin Bonding
by Mohammad H. AlRefeai, Eman M. AlHamdan, Samar Al-Saleh, Abdulaziz S. Alqahtani, Mohammad Q. Al-Rifaiy, Ibraheem F. Alshiddi, Imran Farooq, Fahim Vohra and Tariq Abduljabbar
Polymers 2021, 13(17), 2855; https://doi.org/10.3390/polym13172855 - 25 Aug 2021
Cited by 8 | Viewed by 1935
Abstract
The study aimed at synthesizing β-tricalcium phosphate (β-TCP) nanoparticles and comparing the mechanical properties and dentin interaction of two adhesives: experimental adhesive (EA) and EA with 5 wt.% β-TCP nanoparticles (β-TCP-5%). These filler nanoparticles were synthesized and then characterized with scanning electron microscopy [...] Read more.
The study aimed at synthesizing β-tricalcium phosphate (β-TCP) nanoparticles and comparing the mechanical properties and dentin interaction of two adhesives: experimental adhesive (EA) and EA with 5 wt.% β-TCP nanoparticles (β-TCP-5%). These filler nanoparticles were synthesized and then characterized with scanning electron microscopy (SEM) and micro-Raman spectroscopy. The β-TCP nanoparticles were incorporated in the adhesives to form two groups: gp-1: EA (control) and gp-2: β-TCP-5%. These adhesives were characterized by SEM, energy-dispersive X-ray (EDX) spectroscopy and were also assessed for their micro-tensile bond strength (μTBS) with (TC) and without thermocycling (NTC). Fourier Transform Infrared (FTIR) spectroscopy was performed to evaluate the degree of conversion (DC) of two adhesives. The β-TCP filler was seen as irregularly shaped agglomerates on SEM. The micro-Raman spectra revealed characteristic peaks associated with β-TCP nanoparticles. Both adhesives presented suitable dentin interaction, which was demonstrated by the formation of resin tags of variable depths. The EDX analysis verified the existence of calcium (Ca) and phosphate (P) for the β-TCP-5% group. The greatest μTBS values were shown by β-TCP-5% group samples when they were non-thermocycled (NTC) (β-TCP-5%-NTC: 34.11 ± 3.46) followed by the thermocycled (TC) samples of the same group (β-TCP-5%-TC: 30.38 ± 3.66), compared with the EA group. Although the DC presented by β-TCP-5% group was comparable to the EA group, it was still lower. The addition of β-TCP nanoparticles in the adhesive improved its μTBS and resulted in a suitable dentin interaction, seen in the form of hybrid layer and resin tag formation. Nonetheless, a decreased DC was observed for the β-TCP-5% adhesive. Future studies probing the effect of different filler concentrations on various properties of the adhesive are warranted. Full article
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15 pages, 429 KiB  
Article
Evaluation of the Water Sorption and Solubility Behavior of Different Polymeric Luting Materials
by Nawaf Labban, Rasha AlSheikh, Melvin Lund, Bruce A. Matis, B. Keith Moore, Michael A. Cochran and Jeffrey A. Platt
Polymers 2021, 13(17), 2851; https://doi.org/10.3390/polym13172851 - 25 Aug 2021
Cited by 6 | Viewed by 2287
Abstract
Objective: The study evaluated the water sorption (WSP) and water solubility (WSL) characteristics of different luting agents over a 180-day water storage period. Materials and Methods: Nine luting materials, i.e., conventional resin cement: Panavia F (PF), Rely X ARC (RA), self-adhesive [...] Read more.
Objective: The study evaluated the water sorption (WSP) and water solubility (WSL) characteristics of different luting agents over a 180-day water storage period. Materials and Methods: Nine luting materials, i.e., conventional resin cement: Panavia F (PF), Rely X ARC (RA), self-adhesive resin cement: Rely X Unicem (RU), Breez (BZ), Maxcem Elite (MX), BisCem (BC) and resin-modified glass ionomer cement: FujiCem (FC), FujiPlus (FP) Rely X luting plus (RL) were assessed and fifty-two-disc specimens of each material were fabricated. All specimens were desiccated until a constant weight (W0) was reached. Thirteen specimens for each luting material were then randomly assigned to one of the four water immersion periods (7, 30, 90, and 180 days). After each period, the specimens were removed from the water and weighed to get W1. The samples were again desiccated for a second time and W2 was measured. Both WSP and WSL were determined by the following equations: WSP (%) = (W1 − W2) × 100/W0 and WSL (%) = (W0 − W2) × 100/W0. Assessments were performed following ISO standards. ANOVA was used to assess the effect of luting agent and time period on water sorption and solubility. Pair-wise comparisons were adjusted using Tukey’s multiple comparison procedure. A significance level of 0.05 was used for all statistical tests. Results: The highest mean WSP and WSL (WSP/WSL) were demonstrated by resin-modified glass-ionomers (RL 18.32/3.25, FC 17.08/4.83, and FP 14.14/1.99), while resin luting agents showed lower WSP and WSL results (PF 1.6/0.67 and RA 1.76/0.46), respectively. The self-adhesive agents exhibited a wide range of WSP and WSL values (RU 1.86/0.13, BZ 4.66/0.93, and MX 3.68/1.11). Self-adhesive cement showed lower WSP and WSL compared with the resin-modified glass-ionomers (p < 0.05). All the materials reached equilibrium after 90-days. Conclusions: Resin-based luting materials have the lowest sorption and solubility. Rely X Unicem self-adhesive luting materials were comparable to resin luting materials for WSL and WSP. Resin-modified glass-ionomer showed the highest water sorption and solubility compared with both resin and self-adhesive materials. Full article
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13 pages, 966 KiB  
Article
The Influence of Modified Experimental Dental Resin Composites on the Initial In Situ Biofilm—A Triple-Blinded, Randomized, Controlled Split-Mouth Trial
by Niklas Burgard, Melanie Kienitz, Claudia Jourdan and Stefan Rüttermann
Polymers 2021, 13(16), 2814; https://doi.org/10.3390/polym13162814 - 21 Aug 2021
Cited by 2 | Viewed by 2046
Abstract
The purpose of the study was to investigate the bacterial viability of the initial biofilm on the surface of experimental modified dental resin composites. Twenty-five healthy individuals with good oral hygiene were included in this study. In a split-mouth design, they received acrylic [...] Read more.
The purpose of the study was to investigate the bacterial viability of the initial biofilm on the surface of experimental modified dental resin composites. Twenty-five healthy individuals with good oral hygiene were included in this study. In a split-mouth design, they received acrylic splints with five experimental composite resin specimens. Four of them were modified with either a novel polymeric hollow-bead delivery system or methacrylated polymerizable Irgasan (Antibacterial B), while one specimen served as an unmodified control (ST). A delivery system based on Poly-Pore® was loaded with one of the active agents: Tego® Protect 5000 (Antiadhesive A), Dimethicone (Antiadhesive B), or Irgasan (Antibacterial A). All study subjects refrained from toothbrushing during the study period. Specimens were detached from the splints after 8 h and given a live/dead staining before fluorescence microscopy. A Friedman test and a post hoc Nemenyi test were applied with a significance level at p < 0.05. In summary, all materials but Antibacterial B showed a significant antibacterial effect compared to ST. The results suggested the role of the materials’ chemistry in the dominance of cell adhesion. In conclusion, dental resin composites with Poly-Pore-loaded active agents showed antibacterial effectiveness in situ. Full article
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12 pages, 47966 KiB  
Article
Characterization of Experimental Short-Fiber-Reinforced Dual-Cure Core Build-Up Resin Composites
by Eija Säilynoja, Sufyan Garoushi, Pekka K. Vallittu and Lippo Lassila
Polymers 2021, 13(14), 2281; https://doi.org/10.3390/polym13142281 - 12 Jul 2021
Cited by 8 | Viewed by 2458
Abstract
As a core build-up material, dual-cured (DC) resin-based composites are becoming popular. The aim of this research was to investigate specific physical and handling properties of new experimental short-fiber-reinforced DC resin composites (SFRCs) in comparison to different commercial, conventional DC materials (e.g., Gradia [...] Read more.
As a core build-up material, dual-cured (DC) resin-based composites are becoming popular. The aim of this research was to investigate specific physical and handling properties of new experimental short-fiber-reinforced DC resin composites (SFRCs) in comparison to different commercial, conventional DC materials (e.g., Gradia Core, Rebilda DC, LuxaCore Z, and Visalys® CemCore). Degree of monomer conversion (DC%) was determined by FTIR-spectrometry using either self- or light-curing mode. The flexural strength, modulus, and fracture toughness were calculated through a three-point bending setup. Viscosity was analyzed at room (22 °C) and mouth (35 °C) temperatures with a rotating disk rheometer. The surface microstructure of each resin composite was examined with scanning electron microscopy (SEM). Data were statistically analyzed with analysis of variance ANOVA (p = 0.05). The curing mode showed significant (p < 0.05) effect on the DC% and flexural properties of tested DC resin composites and differences were material dependent. SFRC exhibited the highest fracture toughness (2.3 MPa m1/2) values and LuxaCore showed the lowest values (1 MPa m1/2) among the tested materials (p < 0.05). After light curing, Gradia Core and SFRCs showed the highest flexural properties (p < 0.05), while the other resin composites had comparable values. The novel DC short-fiber-reinforced core build-up resin composite demonstrated super fracture toughness compared to the tested DC conventional resin composites. Full article
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19 pages, 3154 KiB  
Article
Effect of Ultrasonic Vibration on Structural and Physical Properties of Resin-Based Dental Composites
by Abdul Samad Khan
Polymers 2021, 13(13), 2054; https://doi.org/10.3390/polym13132054 - 23 Jun 2021
Cited by 6 | Viewed by 2334
Abstract
This study aimed to investigate the influence of ultrasonic heat before photo-polymerization on the structural and physical properties of dental composites. Commercially available bulk-fill, nano-hybrid, micro-hybrid, and flowable composites were used. The samples were divided into three groups i.e., (i) without ultrasonic activation, [...] Read more.
This study aimed to investigate the influence of ultrasonic heat before photo-polymerization on the structural and physical properties of dental composites. Commercially available bulk-fill, nano-hybrid, micro-hybrid, and flowable composites were used. The samples were divided into three groups i.e., (i) without ultrasonic activation, (ii) ultrasonic activation at 15 Hz for 30 s, and (iii) ultrasonic activation at 15 Hz for 60 s. The degree of conversion percentage (DC%) and structural changes were evaluated with Fourier transform infrared spectroscopy. The presence of voids in restored tooth cavities were investigated with micro-computed tomography. The statistical analysis was performed using a one-way analysis of variance (ANOVA) post hoc Tukey’s test. The DC% was significantly increased with ultrasonic application in all groups except for flowable composites, whereby flowable composite showed a significant increase with 30 s ultrasonic activation only. The highest DC% was observed in 60 s ultrasonically activated nano-hybrid and micro-hybrid composites. The voids were reduced linearly with ultrasonic application in flowable and bulk-fill composites; however, non-linear behavior was observed with micro-hybrid and nano-hybrid composites, whereby the difference was significant within the groups. The frequency and time of the ultrasonic application is an important factor to consider and can be used to preheat composites before clinical application. Full article
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9 pages, 11982 KiB  
Article
Fracture Behavior of Short Fiber-Reinforced Direct Restorations in Large MOD Cavities
by Márk Fráter, Tekla Sáry, Eszter Vincze-Bandi, András Volom, Gábor Braunitzer, Balázs Szabó P., Sufyan Garoushi and András Forster
Polymers 2021, 13(13), 2040; https://doi.org/10.3390/polym13132040 - 23 Jun 2021
Cited by 20 | Viewed by 3321
Abstract
The aim of this research was to study the impact of using a short fiber-reinforced composite (SFRC) core on the fatigue performance and fracture behavior of direct large posterior composite restorations. Moreover, the influence of the consistency (flowable or packable) of occlusal composite [...] Read more.
The aim of this research was to study the impact of using a short fiber-reinforced composite (SFRC) core on the fatigue performance and fracture behavior of direct large posterior composite restorations. Moreover, the influence of the consistency (flowable or packable) of occlusal composite coverage was assessed. A total of 100 intact molars were collected and randomly distributed into five groups (n = 20). Deep mesio-occlusal-distal (MOD) cavities were prepared in all groups. After adhesive treatment and rebuilding the missing interproximal walls with conventional composite, the specimens in four experimental groups were restored by an SFRC core (everX Flow), which was applied and cured either in bulk or in oblique layers (each 2 mm thick). Packable (G-aenial Posterior) or flowable (G-aenial Injectable) conventional composites were used as a final occlusal layer. The control group was restored with only packable conventional composite. Fatigue survival was measured for all specimens using a cyclic loading machine until a fracture occurred or a total of 25,000 cycles was achieved. Kaplan–Meyer survival analyses were conducted, followed by pairwise log-rank post hoc comparisons. The static load-bearing capacity of surviving teeth was tested using a universal testing machine. Fracture patterns were evaluated visually. There was no statistically significant (p > 0.05) difference in terms of survival between the tested groups. All groups for which flowable SFRC was used showed statistically significantly higher load-bearing capacities compared to the control group (p < 0.05). There were no significant differences regarding fracture resistance among the fiber-reinforced study groups. Regarding the fracture pattern during the survival analysis, all specimens that received SFRC showed a dominantly restorable type of fracture, while the control specimens presented a dominantly non-restorable type. The use of flowable SFRC as a reinforcing core for large MOD direct restorations showed promising achievements regarding fracture behavior. Full article
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15 pages, 21479 KiB  
Article
Influence of Different Conditioning Treatments on the Bond Integrity of Root Dentin to rGO Infiltrated Dentin Adhesive. SEM, EDX, FTIR and MicroRaman Study
by Firas K. Alqarawi, Mazen F. Alkahtany, Khalid H. Almadi, Afnan A. Ben Gassem, Faris A. Alshahrani, Mohammad H. AlRefeai, Imran Farooq, Fahim Vohra and Tariq Abduljabbar
Polymers 2021, 13(10), 1555; https://doi.org/10.3390/polym13101555 - 12 May 2021
Cited by 17 | Viewed by 2465
Abstract
The present study aimed to synthesize and equate the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and 5 wt.% reduced graphene oxide rGO) containing adhesive. Scanning electron microscopy (SEM)-Energy-dispersive X-ray spectroscopy (EDX), Micro-Raman spectroscopy, push-out bond strength test, and [...] Read more.
The present study aimed to synthesize and equate the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and 5 wt.% reduced graphene oxide rGO) containing adhesive. Scanning electron microscopy (SEM)-Energy-dispersive X-ray spectroscopy (EDX), Micro-Raman spectroscopy, push-out bond strength test, and Fourier Transform Infrared (FTIR) spectroscopy were employed to study nano-bond strength, degree of conversion (DC), and adhesive-dentin interaction. The EA was prepared, and rGO particles were added to produce two adhesive groups, EA-rGO-0% (control) and rGO-5%. The canals of sixty roots were shaped and prepared, and fiber posts were cemented. The specimens were further alienated into groups based on the root canal disinfection technique, including 2.5% sodium hypochlorite (NaOCl), Photodynamic therapy (PDT), and ER-CR-YSGG laser (ECYL). The rGO nanoparticles were flake-shaped, and EDX confirmed the presence of carbon (C). Micro-Raman spectroscopy revealed distinct peaks for graphene. Push-out bond strength test demonstrated highest values for the EA-rGO-0% group after NaOCl and PDT conditioning whereas, rGO-5% showed higher values after ECYL conditioning. EA-rGO-0% presented greater DC than rGO-5% adhesive. The rGO-5% adhesive demonstrated comparable push-out bond strength and rheological properties to the controls. The rGO-5% demonstrated acceptable DC (although lower than control group), appropriate dentin interaction, and resin tag establishment. Full article
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12 pages, 2001 KiB  
Article
Influence of Post-Core and Crown Type on the Fracture Resistance of Incisors Submitted to Quasistatic Loading
by Sadullah Uctasli, Yakup Boz, Sercan Sungur, Pekka K. Vallittu, Sufyan Garoushi and Lippo Lassila
Polymers 2021, 13(7), 1130; https://doi.org/10.3390/polym13071130 - 2 Apr 2021
Cited by 18 | Viewed by 5408
Abstract
The aim of this paper was to evaluate the fracture resistance and failure type of maxillary incisor teeth, rebuilt with various types of post-core restorations and full crowns made of either direct conventional particulate filler composite (PFC, G-aenial Anterior, GC, Tokyo, Japan) or [...] Read more.
The aim of this paper was to evaluate the fracture resistance and failure type of maxillary incisor teeth, rebuilt with various types of post-core restorations and full crowns made of either direct conventional particulate filler composite (PFC, G-aenial Anterior, GC, Tokyo, Japan) or indirect CAD/CAM restorations (composite Cerasmart 270 and glass ceramic LiSi Block from GC). One hundred (n = 10/group) central incisors were cut and divided into 10 experimental groups restored with different approaches. In approach A, teeth were restored with a core build-up composite (Gradia Core, GC) for a core and full crown of PFC. Approach B had teeth restored using composite core and prefabricated fiber posts, and a complete crown of either PFC or CAD/CAM. Approach C contained teeth restored with a core of short fiber-reinforced composite (everX Flow, GC) and prefabricated fiber posts, and a complete crown of either PFC or CAD/CAM. In approach D, the teeth had a core of short fiber-reinforced composite only, and a complete crown of either PFC or CAD/CAM restorations. The root canals were prepared, and when posts were used, they were luted with either a dual-cure resin cement (LinkForce, GC) or everX Flow. As the control, sound teeth (n = 10) were used. Restorations were quasi-statically loaded until fracture. Failure type was visually investigated. The interface between the fiber post and luting cement was investigated using SEM, before and after completion of the loading test. The data were analyzed by analysis of variance (p = 0.05) followed by Tukey’s test. None of the restorative approaches restored the fracture load strength of intact teeth (p < 0.05). Restorations with additional fiber posts (Approaches B and C) had higher load-bearing capacity (p < 0.05) than restorations without fiber posts (Approaches A and D). Restorations that had short fiber-reinforced composite cores with or without fiber posts presented more repairable failures. Using short fiber-reinforced composite as post-luting and core build-up material with conventional fiber posts proved to be a promising method to strengthen severely damaged incisors. Full article
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Review

Jump to: Research

13 pages, 685 KiB  
Review
An Updated Review of Salivary pH Effects on Polymethyl Methacrylate (PMMA)-Based Removable Dental Prostheses
by Faris A. Alshahrani, Fatemah AlToraibily, Maryam Alzaid, Amr A. Mahrous, Maram A. Al Ghamdi and Mohammed M. Gad
Polymers 2022, 14(16), 3387; https://doi.org/10.3390/polym14163387 - 19 Aug 2022
Cited by 8 | Viewed by 2552
Abstract
Salivary pH is a neglected factor that may affect the performance of removable dental prostheses (RDP). This study aimed to review literature in reference to the role of salivary pH on the performance of RDP and materials used for their fabrication. From January [...] Read more.
Salivary pH is a neglected factor that may affect the performance of removable dental prostheses (RDP). This study aimed to review literature in reference to the role of salivary pH on the performance of RDP and materials used for their fabrication. From January 1990 until December 2021, a search was done on PubMed, Scopus, and Web of Science databases using removable dental prostheses, salivary pH, PMMA, Denture base, and physical properties as keywords. Articles that met the inclusion criteria (full-length articles have investigated the effect of salivary pH on RDP materials in vitro and in vivo) were included. Out of 433 articles, 8 articles that met the inclusion criteria were included. All studies used artificial saliva with different salivary pH ranging between 3 and 14. Two articles investigated the role of salivary pH on the cytotoxicity of denture base resins and soft liner. One article studied the durability and retention of attachments, one article analyzed the performance of PEEK materials, one article researched the fatigue resistance of a denture base, one article investigated the corrosion of RPD framework cast and milled Co–Cr, one article studied the strength and clasp retention and deformation of acetal and PEEK materials, and one evaluated changes in mass and surface morphology of CAD–CAM fiber-reinforced composites for the prosthetic framework. Different salivary pH affected all included materials in this review except PEEK materials. The most adverse effect was reported with alkaline and acidic; however, the acidic showed the most deterioration effect. Salivary pH has a role in the selection of material used for RDP fabrication. Full article
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26 pages, 845 KiB  
Review
Remineralizing Effects of Resin-Based Dental Sealants: A Systematic Review of In Vitro Studies
by Maha Ibrahim AlGhannam, Mana’a Saleh AlAbbas, Jumanah Abdulla AlJishi, Muath Abdulrahman AlRuwaili, Jehan AlHumaid and Maria Salem Ibrahim
Polymers 2022, 14(4), 779; https://doi.org/10.3390/polym14040779 - 17 Feb 2022
Cited by 9 | Viewed by 3146
Abstract
The incorporation of remineralizing additives into sealants has been considered as a feasible way to prevent caries by potential remineralization through ions release. Thus, this systematic review aimed to identify the remineralizing additives in resin-based sealants (RBS) and assess their performance. Search strategies [...] Read more.
The incorporation of remineralizing additives into sealants has been considered as a feasible way to prevent caries by potential remineralization through ions release. Thus, this systematic review aimed to identify the remineralizing additives in resin-based sealants (RBS) and assess their performance. Search strategies were built to search four databases (PubMed, MEDLINE, Web of Science and Scopus). The last search was conducted in June 2020. The screening, data extraction and quality assessment were completed by two independent reviewers. From the 8052 screened studies, 275 full-text articles were assessed for eligibility. A total of 39 laboratory studies matched the inclusion criteria. The methodologies used to assess the remineralizing effect included microhardness tests, micro-computed tomography, polarized-light microscopy, ions analysis and pH measurements. Calcium phosphate (CaP), fluoride (F), boron nitride nanotubes (BNN), calcium silicate (CS) and hydroxyapatite (HAP) were incorporated into resin-based sealants in order to improve their remineralizing abilities. Out of the 39 studies, 32 studies focused on F as a remineralizing agent. Most of the studies confirmed the effectiveness of F and CaP on enamel remineralization. On the other hand, BNN and CS showed a small or insignificant effect on remineralization. However, most of the included studies focused on the short-term effects of these additives, as the peak of the ions release and concentration of these additives was seen during the first 24 h. Due to the lack of a standardized in vitro study protocol, a meta-analysis was not conducted. In conclusion, studies have confirmed the effectiveness of the incorporation of remineralizing agents into RBSs. However, the careful interpretation of these results is recommended due to the variations in the studies’ settings and assessments. Full article
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12 pages, 429 KiB  
Review
Effect of Fiber Reinforcement Type on the Performance of Large Posterior Restorations: A Review of In Vitro Studies
by Enas Mangoush, Sufyan Garoushi, Lippo Lassila, Pekka K. Vallittu and Eija Säilynoja
Polymers 2021, 13(21), 3682; https://doi.org/10.3390/polym13213682 - 26 Oct 2021
Cited by 13 | Viewed by 4473
Abstract
To reinforce extensively prepared cavities, different types of fiber reinforcement are utilized. Polyethylene and glass fibers are the most commonly used fibers in that purpose; each type has its own advantages over the other type. Therefore, the aim of this study is to [...] Read more.
To reinforce extensively prepared cavities, different types of fiber reinforcement are utilized. Polyethylene and glass fibers are the most commonly used fibers in that purpose; each type has its own advantages over the other type. Therefore, the aim of this study is to review the literature to evaluate and compare the influence of different fiber reinforcement types on the performance of posterior large composite restorations. Two independent authors performed a comprehensive literature search using MEDLINE/PubMed, Google Scholar, and a manual search for cross references until July 2021. Authors selected only studies that contain comparisons between glass (continuous or short) and polyethylene (woven) fiber-reinforced composites (FRCs) in posterior cavities of human teeth, and that report the effect of fiber inclusion on fracture resistance, microleakage, and marginal adaptation of restorations. A number of 2711 potentially relevant articles were obtained from the electronic search. After extensive assessment, 2696 articles were ineligible to be included in the review, and only 15 articles met the inclusion criteria. Four out of nine studies, which tested the fracture resistance of FRC restorations, revealed similar performance of the glass and polyethylene fibers. The rest of the studies (n = 5) revealed statistically significant differences between the two types of fiber reinforcement, with the majority showed superior reinforcement of glass fiber. Moreover, the reviewed studies revealed that, using fibers within the composite restorations would reduce the microleakage and improve the marginal adaptation of the restoration regardless of the fiber type. FRCs tend to strengthen the restorations of structurally compromised teeth and improve their performance compared to plain composite restorations. Full article
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9 pages, 826 KiB  
Review
Effect of Composite Core Materials on Fracture Resistance of Endodontically Treated Teeth: A Systematic Review and Meta-Analysis of In Vitro Studies
by Maciej Zarow, Marzena Dominiak, Katarzyna Szczeklik, Louis Hardan, Rim Bourgi, Carlos Enrique Cuevas-Suárez, Juan Eliezer Zamarripa-Calderón, Naji Kharouf and Dimitar Filtchev
Polymers 2021, 13(14), 2251; https://doi.org/10.3390/polym13142251 - 9 Jul 2021
Cited by 15 | Viewed by 3681
Abstract
Various material properties are involved in the success of endodontically treated restorations. At present, restorative composites are commonly employed as core build-up materials. This study aimed to systematically review the literature to assess the effect of using composite core materials on the in [...] Read more.
Various material properties are involved in the success of endodontically treated restorations. At present, restorative composites are commonly employed as core build-up materials. This study aimed to systematically review the literature to assess the effect of using composite core materials on the in vitro fracture of endodontically treated teeth. Two different reviewers screened the literature, up to June 2021, in five distinct electronic databases: PubMed (MedLine), Scopus, Scielo, ISI Web of Science, and EMBASE. Only in vitro studies reporting the effect of the use of composite core materials on the fracture resistance of endodontically treated teeth were included. A meta-analysis was carried out using a software program (Review Manager v5.4.1; The Cochrane Collaboration, Copenhagen, Denmark). The risk of bias in each study was assessed following the parameters of another systematic review. A total of 5016 relevant papers were retrieved from all databases. After assessing the title and abstract, five publications remained for qualitative analysis. From these, only three studies remained for meta-analysis. The fracture strength of endodontically treated teeth where a core build-up composite was used was statistically significantly higher than the control (p = 0.04). Most of the analyses showed a high heterogenicity. The in vitro evidence suggests that the composite core build-up with higher filler content tended to improve the fracture resistance of the endodontically treated teeth, in comparison with conventional composite resins. This research received no external funding. Considering that this systematic review was only carried out on in vitro papers, registration was not performed. Furthermore, there were no identified clinical studies assessing core build-up materials; therefore, more well-designed research on these materials is needed. Full article
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