Special Issue "Polymers for Oral and Dental Health"

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

Deadline for manuscript submissions: closed (28 November 2021).

Special Issue Editors

Prof. Dr. Andrea Scribante
E-Mail Website
Guest Editor
Unit of Orthodontics and Paediatric Dentistry, Section of Dentistry, Department of Clinical, Surgical, Diagnostic and Paediatric Sciences, University of Pavia, 27100 Pavia, Italy
Interests: orthodontics; adhesive dentistry; dental materials; adhesive dentistry; CAD/CAM; intraoral scanner; computerized cast; shear; bond strength; bracket; fiber-reinforced composite; miniscrew
Special Issues, Collections and Topics in MDPI journals
Dr. Simone Gallo
E-Mail Website
Co-Guest Editor
Department of Clinical, Surgical, Diagnostic and Paediatric Sciences, Section of Dentistry, University of Pavia, Pavia, Italy
Interests: Polymeric dental materials; Dentistry; polymeric adhesion; Orthodontics

Special Issue Information

Dear Colleagues,

Polymers represent a widespread category of materials with applications both in medicine and in dentistry, and this is attributed not only to their surface characteristics but also their mechanical and biological properties, along with easy processability and low cost. They consist of high-molecular-mass macromolecules formed by the repetition of the respective monomers. In dentistry, some of the most commonly used polymers are polyethylene (PE), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene glycol (PEG), polydimethylsiloxane (PDMS), polyurethane (PUR), polylactic acid (PLLA), poly(e-caprolactone) (PCL), polypyrrole (PPy), hexamethyldisilazane (HMDS), N-isopropylacrylamide (NIPAM), and N-tert-butylacrylamide (TBA). The mechanical properties of these biomaterials are related to their bulk characteristics; however, their interaction with tissues strictly depends on their surface, which justifies the possibility of using polymer coatings to increase the biocompatibility of bulk materials.

Considering the specific applications of polymers, these cover almost every field of dentistry. The current restorative procedures are based on restorations with composite resins that are made of monomers that become polymeric after photopolymerization. This is the same for dental adhesives, which represent a prerequisite to guarantee the adhesion of restorations to the dental surface, as well as that of brackets and retainers in orthodontics. Moreover, cements like resin-modified glass-ionomers, which contain a resinous component, are used for the adhesion of orthodontic bands to posterior teeth besides having many applications in pedodontics. In addition, fiber-reinforced composites are used for post-orthodontic tooth retention and for splinting mobile teeth.

Polymeric materials are also encountered in prosthodontics, for example, with acrylic resins dentures and with adhesives for metal or ceramic, and polymers are suitable as 3D-printing materials due to their versatility. Recently, the synthetic polyetheretherketone (PEEK) has also been proposed as a new implant material.

Finally, polymers (even of natural origin) are also used to fabricate scaffolds, inducing an in situ regeneration of dentin- and pulp-like tissues, to realize membranes for guided tissue regeneration (GTR), and then as delivery systems of various drugs or bioactive macromolecules to treat different oral and periodontal pathologies.

In conclusion, polymer-based materials are playing a central role in dentistry and knowledge of their properties should be improved to take advantage of further potentialities in clinical practice. Therefore, it is our pleasure to invite you to submit a manuscript for this Special Issue on developments and applications of polymeric materials in dentistry. Full papers, communications, and reviews are welcome.

Potential topics include but are not limited to the following:

  • Polymer-based dental materials
  • Resin composites
  • Adhesives
  • Restorative dentistry
  • Prosthodontics
  • Orthodontics
  • Pediatric dentistry
  • Regenerative therapies
  • Drug delivery systems

Please refer to the non-exhaustive list of keywords for further hints.

Prof. Dr. Andrea Scribante
Dr. Simone Gallo
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polymers
  • dentistry
  • dental materials
  • restorative
  • resin
  • composite
  • adhesive
  • orthodontics
  • regenerative therapies
  • drug delivery

Published Papers (8 papers)

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Research

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Article
SEM/EDS Evaluation of the Mineral Deposition on a Polymeric Composite Resin of a Toothpaste Containing Biomimetic Zn-Carbonate Hydroxyapatite (microRepair®) in Oral Environment: A Randomized Clinical Trial
Polymers 2021, 13(16), 2740; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13162740 - 16 Aug 2021
Cited by 1 | Viewed by 749
Abstract
Toothpastes containing biomimetic hydroxyapatite have been investigated in recent years; the behavior of this material in the oral environment has been evaluated directly on dental enamel showing a marked remineralizing activity. To propose microRepair®-based toothpastes (Zn-carbonate hydroxyapatite) for the domiciliary oral [...] Read more.
Toothpastes containing biomimetic hydroxyapatite have been investigated in recent years; the behavior of this material in the oral environment has been evaluated directly on dental enamel showing a marked remineralizing activity. To propose microRepair®-based toothpastes (Zn-carbonate hydroxyapatite) for the domiciliary oral hygiene in patients with dental composite restorations, the aim of this study was to evaluate the deposition of Zn-carbonate hydroxyapatite on a polymeric composite resin with Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry (SEM/EDS) analysis. Twenty healthy volunteers underwent the bonding of 3 orthodontic buttons on the vestibular surfaces of upper right premolars and first molar. On the surface of the buttons, a ball-shaped mass of composite resin was applied and light-cured. Then, the volunteers were randomly divided into two groups according to the toothpaste used for domiciliary oral hygiene: the Control toothpaste containing stannous fluoride and the Trial toothpaste containing microRepair®. The buttons were debonded after 7 days (T1—first premolar), after 15 days (T2—second premolar), and after 30 days (T3—first molar) to undergo the SEM/EDS analysis. The deposition of calcium, phosphorus, and silicon was assessed through EDS analysis and data were submitted to statistical analysis (p < 0.05). SEM morphologic evaluation showed a marked deposition of the two toothpastes on the surfaces of the buttons. EDS quantitative analysis showed an increase of calcium, phosphorus, and silicon in both the groups, with a statistically significant difference of calcium deposition at T3 for the Trial group. Therefore, the use of toothpaste containing Zn-carbonate hydroxyapatite could be proposed as a device for domiciliary oral hygiene because the deposition of hydroxyapatite on polymeric composite resin could prevent secondary caries on the margins of restorations. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Article
Assessment of Bond Integrity, Durability, and Degree of Conversion of a Calcium Fluoride Reinforced Dentin Adhesive
Polymers 2021, 13(15), 2418; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13152418 - 23 Jul 2021
Viewed by 728
Abstract
Our study aimed to synthesize and compare the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and EA containing 5 wt.% calcium fluoride (CaF2) nano-crystals (CaF2 adhesive-CAFA). CaF2 nano-crystals were synthesized by reacting two solutions (containing [...] Read more.
Our study aimed to synthesize and compare the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and EA containing 5 wt.% calcium fluoride (CaF2) nano-crystals (CaF2 adhesive-CAFA). CaF2 nano-crystals were synthesized by reacting two solutions (containing calcium and fluoride) in a glass chamber using a heated air system. The EA was produced using a mix of monomers, photo-initiators, camphorquinone, and electron initiators. The synthesized CaF2 nano-crystals were centrifuged to guarantee that inside the adhesive there is homogenized dispersion of the filler particles. Their integration in the EA yielded two groups; Gp-1: EA (without CaF2, control) and Gp-2: (5 wt.% CaF2 containing adhesive, CAFA). Sixty teeth were prepared and set to form bonded specimens using the two adhesives. The CaF2 nano-crystals were irregularly shaped with an average particle size of 30–200 nm. The highest μTBS values were obtained for CAFA-non-thermocycled (NTC) samples (32.63 ± 3.15), followed by EA-NTC (31.80 ± 3.75) specimens. On thermocycling (TC), both adhesive groups presented lower μTBS values (CAFA-TC: 29.47 ± 3.33 and EA-TC: 24.04 ± 3.69). Hybrid layer (HL) formation and resin tags of varying depths were perceived for both adhesive groups. The EDX analysis demonstrated the presence of carbon (C), silica (Si), calcium (Ca), and fluoride (F) for CAFA group. Micro-Raman spectroscopy revealed distinct peaks for CaF2 nano-crystals. The CAFA group presented the greatest DC. The addition of CaF2 nano-crystals in the adhesive caused improved bond μTBS and DC. The incorporation also demonstrated suitable dentin interaction, depicted by appropriate HL and resin tag development. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Communication
Influence of Polymeric Restorative Materials on the Stress Distribution in Posterior Fixed Partial Dentures: 3D Finite Element Analysis
Polymers 2021, 13(5), 758; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13050758 - 28 Feb 2021
Cited by 5 | Viewed by 1046
Abstract
Background: This study evaluated the effect of interim restorative materials (acrylic resin (AR), resin composite (RC) or polyetheretherketone (PEEK) for dental computer-aided design/computer-aided manufacturing (CAD/CAM)) on the stress distribution of a posterior three-unit fixed partial denture. Methods: The abutment teeth (first molar and [...] Read more.
Background: This study evaluated the effect of interim restorative materials (acrylic resin (AR), resin composite (RC) or polyetheretherketone (PEEK) for dental computer-aided design/computer-aided manufacturing (CAD/CAM)) on the stress distribution of a posterior three-unit fixed partial denture. Methods: The abutment teeth (first molar and first premolar) were modeled using the BioCAD protocol containing 1.5 mm of axial reduction and converging axial walls. A static structural analysis was performed in the computer-aided engineering software, and the Maximum Principal Stress criterion was used to analyze the prosthesis and the cement layers of both abutment teeth. The materials were considered isotropic, linearly elastic, homogeneous and with bonded contacts. An axial load (600 N) was applied to the occlusal surface of the second premolar. Results: Regardless of the restorative material, the region of the prosthetic connectors showed the highest tensile stress magnitude. The highest stress peak was observed with the use of RC (129 MPa) compared to PEEK and AR. For the cement layers, RC showed the lowest values in the occlusal region (7 MPa) and the highest values for the cervical margin (14 MPa) compared to PEEK (21 and 12 MPa) and AR (21 and 13 MPa). Conclusions: Different interim restorative materials for posterior fixed partial dentures present different biomechanical behavior. The use of resin composite can attenuate the stress magnitude on the cement layer, and the use of acrylic resin can attenuate the stress magnitude on the connector region. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Article
TEGDMA (Triethylene Glycol Dimethacrylate) Induces Both Caspase-Dependent and Caspase-Independent Apoptotic Pathways in Pulp Cells
Polymers 2021, 13(5), 699; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13050699 - 25 Feb 2021
Viewed by 498
Abstract
Monomers leached from resin-based composites (RBCs) may reach intrapulpal concentrations of the millimolar (mM) range, which could contribute to inflammation. The aim of this investigation was to assess the cytotoxicity of triethylene glycol dimethacrylate (TEGDMA) monomers on pulp cells as well as to [...] Read more.
Monomers leached from resin-based composites (RBCs) may reach intrapulpal concentrations of the millimolar (mM) range, which could contribute to inflammation. The aim of this investigation was to assess the cytotoxicity of triethylene glycol dimethacrylate (TEGDMA) monomers on pulp cells as well as to identify molecular mechanisms leading to apoptosis. Pulp cells were harvested from molars extracted for orthodontic reasons and cultured through an explant method. To assess cytotoxicity, cells underwent a 5-day exposure to 0.75, 1.5, and 3 mM TEGDMA and were subject to cell counting and WST-1 staining. Based on the findings, cells were subsequently exposed to 0.1, 0.2, 0.75, 1.5, and 3 mM TEGDMA for 24 h to uncover the details of apoptosis. Changes in the production or cleavage of the apoptosis-specific proteins caspase-8, caspase-9, caspase-3, caspase-12, and Apoptosis-Inducing Factor (AIF) were measured by Western blot. The 5-day study showed concentration- and time-dependent cytotoxicity. Significant cell death was detected after 24 h with TEGDMA concentrations of 1.5 and 3 mM. One-day exposure to TEGDMA led to the activation of caspase-8, -9, -3, and -12 and an increased AIF production. Results suggest that relevant concentrations of TEGDMA monomers, leached from RBCs, induce apoptosis in pulp cells through both caspase-dependent as well as caspase-independent mechanisms. Endoplasmic reticulum stress and the activation of caspase-independent apoptotic pathways may be further mechanisms by which monomers induce apoptosis in pulp cells. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Article
Bonding and Thermal Cycling Performances of Two (Poly)Aryl–Ether–Ketone (PAEKs) Materials to an Acrylic Denture Base Resin
Polymers 2021, 13(4), 543; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13040543 - 12 Feb 2021
Cited by 1 | Viewed by 808
Abstract
Poly(aryl–ether–ketone) materials (PAEKs) are gaining interest in everyday dental practices because of their natural properties. This study aims to analyze the bonding performance of PAEKs to a denture acrylic. Testing materials were pretreated by grinding, sandblasting, and priming prior to polymerization with the [...] Read more.
Poly(aryl–ether–ketone) materials (PAEKs) are gaining interest in everyday dental practices because of their natural properties. This study aims to analyze the bonding performance of PAEKs to a denture acrylic. Testing materials were pretreated by grinding, sandblasting, and priming prior to polymerization with the denture acrylic. The surface morphologies were observed using a scanning electron microscope and the surface roughness was measured using atomic force microscopy. The shear bond strength (SBS) values were determined after 0 and 2500 thermal cycles. The obtained data were analyzed using a paired samples t-test and Tukey’s honestly significant difference (HSD) test (α = 0.05). The surface characteristics of testing materials after different surface pretreatments showed obvious differences. PAEKs showed lower surface roughness values (0.02–0.03 MPa) than Co-Cr (0.16 MPa) and zirconia (0.22 MPa) after priming and sandblasting treatments (p < 0.05). The SBS values of PAEKs (7.60–8.38 MPa) met the clinical requirements suggested by ISO 10477 (5 MPa). Moreover, PAEKs showed significantly lower SBS reductions (p < 0.05) after thermal cycling fatigue testing compared to Co-Cr and zirconia. Bonding performance is essential for denture materials, and our results demonstrated that PAEKs possess good resistance to thermal cycling fatigue, which is an advantage in clinical applications. The results imply that PAEKs are potential alternative materials for the removable of prosthetic frameworks. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Article
Microwave-Assisted Fabrication of Mesoporous Silica-Calcium Phosphate Composites for Dental Application
Polymers 2021, 13(1), 53; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13010053 - 25 Dec 2020
Cited by 4 | Viewed by 841
Abstract
Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized [...] Read more.
Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized in terms of molecular structure, crystallinity, morphology, chemical composition, and mineralization potential by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). The application of microwave irradiation resulted in the formation of different types of calcium orthophosphates such as calcium deficient hydroxyapatite (CDHA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP) on the SBA-15 surface, depending on the type of coating solution. The composites for which the progressive formation of hydroxyapatite during incubation in simulated body fluid was observed were further used in the production of final pharmaceutical forms: membranes, granules, and pellets. All of the obtained pharmaceutical forms preserved mineralization properties. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Article
Effect of Over-Etching and Prolonged Application Time of a Universal Adhesive on Dentin Bond Strength
Polymers 2020, 12(12), 2902; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12122902 - 03 Dec 2020
Cited by 3 | Viewed by 732
Abstract
This study investigated the effect of over-etching and prolonged application time of a universal adhesive on dentin bond strength. Ninety extracted human molars were ground to dentin and randomly allocated into nine groups (G1–9; n = 10 per group), according to the following [...] Read more.
This study investigated the effect of over-etching and prolonged application time of a universal adhesive on dentin bond strength. Ninety extracted human molars were ground to dentin and randomly allocated into nine groups (G1–9; n = 10 per group), according to the following acid etching and adhesive application times. In the control group (G1), phosphoric acid etching was performed for 15 s followed by application of the universal adhesive Scotchbond Universal (3M) for 20 s, as per manufacturer’s instructions. In groups G2–5, both the etching and adhesive application times were either halved, doubled, quadrupled, or increased eightfold. In groups G6–9, etching times remained the same as in G2–5 (7.5 s, 30 s, 60 s, and 120 s, respectively), but the adhesive application time was set at 20 s as in the control group (G1). Specimens were then restored with a nanofilled composite material and subjected to microtensile bond strength testing. Bond strength data were statistically analyzed by ANOVA and Tukey’s post-hoc tests (α = 0.05). The relationship of bond strength with etching and adhesive application time was examined using linear regression analysis. Treatment of dentin with halved phosphoric acid etching and adhesive application times (G2) resulted in a significant bond strength decrease compared to the control group (G1) and all other test groups, including the group with halved acid etching, but 20 s of adhesive application time (G6). No significant differences in bond strength were found for groups with multiplied etching times and an adhesive application time of 20 s or more, when compared to the control group (G1). In conclusion, a universal adhesive application time of at least 20 s is recommended when bonding to over-etched dentin. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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Review

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Review
Bond Strength of Universal Adhesives to Dentin: A Systematic Review and Meta-Analysis
Polymers 2021, 13(5), 814; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13050814 - 07 Mar 2021
Cited by 6 | Viewed by 2177
Abstract
Currently, the availability of a wide variety of universal adhesives makes it difficult for clinicians to choose the correct system for specific bonding situations to dentin substrate. This study aimed to determine whether there are any alternative techniques or additional strategies available to [...] Read more.
Currently, the availability of a wide variety of universal adhesives makes it difficult for clinicians to choose the correct system for specific bonding situations to dentin substrate. This study aimed to determine whether there are any alternative techniques or additional strategies available to enhance the bond strength of universal adhesives to dentin through a systematic review and meta-analysis. Two reviewers executed a literature search up to September 2020 in four electronic databases: PubMed, ISI Web of Science, Scopus, and EMBASE. Only in vitro studies that reported the dentin bond strength of universal adhesives using additional strategies were included. An analysis was carried out using Review Manager Software version 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). The methodological quality of each in vitro study was assessed according to the parameters of a previous systematic. A total of 5671 potentially relevant studies were identified. After title and abstract examination, 74 studies remained in systematic review. From these, a total of 61 studies were included in the meta-analysis. The bond strength of universal adhesives to dentin was improved by the use of one of the following techniques: Previous application of matrix metalloproteinases (MMP) inhibitors (p < 0.001), prolonged application time (p = 0.007), scrubbing technique (p < 0.001), selective dentin etching (p < 0.001), non-atmospheric plasma (p = 0.01), ethanol-wet bonding (p < 0.01), prolonged blowing time (p = 0.02), multiple layer application (p = 0.005), prolonged curing time (p = 0.006), and hydrophobic layer coating (p < 0.001). On the other hand, the use of a shortened application time (p = 0.006), and dentin desensitizers (p = 0.01) impaired the bond strength of universal adhesives to dentin. Most of the analyses performed showed a high heterogenicity. The in vitro evidence suggests that the application of universal adhesives using some alternative techniques or additional strategies may be beneficial for improving their bonding performance to dentin. This research received no external funding. Considering that this systematic review was carried out only with in vitro studies, registration was not performed. Full article
(This article belongs to the Special Issue Polymers for Oral and Dental Health)
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