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Wang Z, Zhang X, Yao S, Zhao J, Zhou C, Wu J. Development of low-shrinkage dental adhesives via blending with spiroorthocarbonate expanding monomer and unsaturated epoxy resin monomer. J Mech Behav Biomed Mater 2022; 133:105308. [PMID: 35709601 DOI: 10.1016/j.jmbbm.2022.105308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 11/24/2022]
Abstract
Polymerization shrinkage is one of the main drawbacks of dental resin adhesives. In this study, spiroorthocarbonate expanding monomer 3,9-diethyl-3,9-dimethylol -1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU) and unsaturated epoxy resin monomer Diallyl bisphenol A diglycidyl ether (DBDE) were synthesized and utilized as anti-shrinkage-coupling additive of methacrylate-based adhesives. Polymerization process and physicochemical properties including double bond conversion, polymerization shrinkage, compatibility, mechanical performance, thermal stability, contact angle, shear bond strength and cytotoxicity were characterized. Results indicated that adhesives containing anti-shrinkage-coupling additive had reduced volume shrinkage, improved compatibility and enhanced shear bond strength. When the amount of additive was 20 wt%, the volume shrinkage was decreased by 45.8% (4.17 ± 0.32%) and the shear bond strength was increased by 49.6% (19.64 ± 0.99 MPa). The results also showed that the use of additive had no adversely affect on double bond conversion and cytotoxicity. Therefore, novel low-shrinkage resin adhesives were prepared via blending with spiroorthocarbonate expanding monomer and unsaturated epoxy resin monomer.
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Affiliation(s)
- Zonghua Wang
- Department of Prosthodontics, School and Hospital of Stomatology, Cheeloo College of Medicine, Shandong University & Shandong Key Laboratory of Oral Tissue Regeneration & Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration, Jinan, 250012, China
| | - Xiaoran Zhang
- Department of Prosthodontics, School and Hospital of Stomatology, Cheeloo College of Medicine, Shandong University & Shandong Key Laboratory of Oral Tissue Regeneration & Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration, Jinan, 250012, China
| | - Shuo Yao
- Department of Prosthodontics, School and Hospital of Stomatology, Cheeloo College of Medicine, Shandong University & Shandong Key Laboratory of Oral Tissue Regeneration & Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration, Jinan, 250012, China
| | - Jiaxin Zhao
- Research Institute of Polymer Materials, School of Materials Science and Engineering, Shandong University, Jinan, 250061, China
| | - Chuanjian Zhou
- Research Institute of Polymer Materials, School of Materials Science and Engineering, Shandong University, Jinan, 250061, China
| | - Junling Wu
- Department of Prosthodontics, School and Hospital of Stomatology, Cheeloo College of Medicine, Shandong University & Shandong Key Laboratory of Oral Tissue Regeneration & Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration, Jinan, 250012, China.
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Zhang X, Wang Z, Yao S, Zhou C, Wu J. Development and Dental Applications of Spiro Expanding Monomers as Antishrinkage Additives. ChemistrySelect 2022. [DOI: 10.1002/slct.202201025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Xiaoran Zhang
- Department of Prosthodontics School and Hospital of Stomatology, Cheeloo College of Medicine Shandong University Shandong Key Laboratory of Oral Tissue Regeneration Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration Jinan 250012 China
| | - Zonghua Wang
- Department of Prosthodontics School and Hospital of Stomatology, Cheeloo College of Medicine Shandong University Shandong Key Laboratory of Oral Tissue Regeneration Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration Jinan 250012 China
| | - Shuo Yao
- Department of Prosthodontics School and Hospital of Stomatology, Cheeloo College of Medicine Shandong University Shandong Key Laboratory of Oral Tissue Regeneration Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration Jinan 250012 China
| | - Chuanjian Zhou
- Research Institute of Polymer Materials School of Materials Science and Engineering Shandong University Jinan 250061 China
| | - Junling Wu
- Department of Prosthodontics School and Hospital of Stomatology, Cheeloo College of Medicine Shandong University Shandong Key Laboratory of Oral Tissue Regeneration Shandong Engineering Laboratory for Dental Materials and Oral Tissue Regeneration Jinan 250012 China
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Utilizing a degradation prediction pathway system to understand how a novel methacrylate derivative polymer with flipped external ester groups retains physico-mechanical properties following esterase exposure. Dent Mater 2022; 38:251-265. [PMID: 34933759 PMCID: PMC8828700 DOI: 10.1016/j.dental.2021.12.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/25/2021] [Accepted: 12/08/2021] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The region of failure for current methacrylates (i.e. derivatives of acrylates) are ester bond linkages that hydrolyze in the presence of salivary and bacterial esterases that break the polymer network backbone. This effect decreases the mechanical properties of methacrylate-based materials. METHODS The ethylene glycol dimethacrylate (EGDMA) or novel ethylene glycol ethyl methacrylate (EGEMA) discs were prepared using 40 µL of the curing mixture containing photo/co-initiators for 40 s in a PTFE mold at 1000 mW/cm2. The degree of conversion was used as a quality control measure for the prepared discs, followed by physical, mechanical, and chemical characterization of discs properties before and after cholesterol esterase treatment. RESULTS After 9 weeks of standardized cholesterol esterase (CEase) exposure, EGDMA discs showed exponential loss of material (p = 0.0296), strength (p = 0.0014) and increased water sorption (p = 0.0002) compared to EGEMA discs. We integrated a degradation prediction pathway system to LC/MS and GC/MS analyses to elucidate the degradation by-products of both EGEMA and EGDMA polymers. GC/MS analysis demonstrated that the esterase catalysis was directed to central polymer backbone breakage, producing ethylene glycol, for EGDMA, and to side chain breakage, producing ethanol, for EGEMA. The flipped external ester group linkage design is attributed to EGEMA showing higher resistance to esterase biodegradation and changes in mechanical and physical properties than EGDMA. SIGNIFICANCE EGEMA is a potential substitute for common macromer diluents, such as EGDMA, based on its resistance to biodegradation effects. This work inspires the flipped external group design to be applied to analogs of current larger, hydrophobic strength bearing macromers used in future dental material formulations.
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Kumar D, Ghose D, Bolskar RD, Mutreja I, Jones RS. A novel methacrylate derivative polymer that resists bacterial cell-mediated biodegradation. J Biomed Mater Res B Appl Biomater 2021; 110:991-1000. [PMID: 34855282 DOI: 10.1002/jbm.b.34972] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 11/02/2021] [Accepted: 11/16/2021] [Indexed: 01/25/2023]
Abstract
This study tests biodegradation resistance of a custom synthesized novel ethylene glycol ethyl methacrylate (EGEMA) with ester bond linkages that are external to the central polymer backbone when polymerized. Ethylene glycol dimethacrylate (EGDMA) with internal ester bond linkages and EGEMA discs were prepared in a polytetrafluoroethylene (PTFE) mold using 40 μl macromer and photo/co-initiator mixture cured for 40 s at 1000 mW/cm2 . The discs were stored in the constant presence of Streptococcus mutans (S. mutans) in Todd Hewitt Yeast + Glucose (THYE+G) media up to 9 weeks (n = 8 for each macromer type) and physical/mechanical properties were assessed. Initial measurements EGEMA versus EGDMA polymer discs showed equivalent degree of conversion (45.69% ± 2.38 vs. 46.79% ± 4.64), diametral tensile stress (DTS; 8.12± 2.92 MPa vs. 6.02 ± 1.48 MPa), and low subsurface optical defects (0.41% ± 0.254% vs. 0.11% ± 0.074%). The initial surface wettability (contact angle) was slightly higher (p ≤ .012) for EGEMA (62.02° ± 3.56) than EGDMA (53.86° ± 5.61°). EGDMA showed higher initial Vicker's hardness than EGEMA (8.03 ± 0.88 HV vs. 5.93 ± 0.69 HV; p ≤ .001). After 9 weeks of S. mutans exposure, EGEMA (ΔDTS-1.30 MPa) showed higher resistance to biodegradation effects with a superior DTS than EGDMA (ΔDTS-6.39 MPa) (p = .0039). Visible and scanning electron microscopy images of EGEMA show less surface cracking and defects than EGDMA. EGDMA had higher loss of material (18.9% vs. 8.5%, p = .0009), relative changes to fracture toughness (92.5% vs. 49.2%, p = .0022) and increased water sorption (6.1% vs. 1.9%, p = .0022) compared to EGEMA discs. The flipped external ester group linkage design is attributed to EGEMA showing higher resistance to bacterial degradation effects than an internal ester group linkage design methacrylate.
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Affiliation(s)
- Dhiraj Kumar
- Department of Surgical and Developmental Sciences, School of Dentistry, University of Minnesota, Minneapolis, Minnesota, USA
| | - Debarati Ghose
- Department of Surgical and Developmental Sciences, School of Dentistry, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Isha Mutreja
- Minnesota Dental Research Center for Biomaterials and Biomechanics, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis, Minnesota, USA
| | - Robert S Jones
- Department of Surgical and Developmental Sciences, School of Dentistry, University of Minnesota, Minneapolis, Minnesota, USA
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Kumar D, Bolskar RD, Malone S, Mutreja I, Aparicio C, Jones RS. A Novel Dental Polymer with a Flipped External Ester Group Design that Resists Degradation via Polymer Backbone Preservation. ACS Biomater Sci Eng 2020; 6:5609-5619. [PMID: 33178887 DOI: 10.1021/acsbiomaterials.0c00947] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Current dental sealants with methacrylate based chemistry are prone to hydrolytic degradation. A conventional ethylene glycol dimethacrylate (EGDMA) was compared to a novel methacrylate monomer with a flipped external ester group (ethylene glycol ethyl methacrylate - EGEMA) that was designed to resist polymer degradation effects. Fourier transform infrared spectroscopy and water contact angle confirmed a comparable degree of initial conversion and surface wettability for EGDMA and EGEMA. EGDMA disks initially performed better compared to EGEMA as suggested by higher surface hardness and 1.5 times higher diametral tensile strength (DTS). After 15 weeks of hydrolytic and accelerated aging, EGDMA and EGEMA DTS was reduced by 88% and 44% respectively. This accelerated aging model resulted in 3.3 times higher water sorption for EDGMA than EGEMA disks. EGDMA had an increase in grain boundary defects and visible erosion sites with accelerated aging, while for EGEMA the changes were not significant.
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Affiliation(s)
- Dhiraj Kumar
- Division of Pediatric Dentistry, School of Dentistry, University of Minnesota, Moos Health Science Tower, 515 Delaware Street S.E. Minneapolis, MN 55455
| | | | - Sydney Malone
- Division of Pediatric Dentistry, School of Dentistry, University of Minnesota, Moos Health Science Tower, 515 Delaware Street S.E. Minneapolis, MN 55455
| | - Isha Mutreja
- Minnesota Dental Research Center for Biomaterials and Biomechanics, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Moos Health Science Tower, 515 Delaware Street S.E. Minneapolis, MN 55455
| | - Conrado Aparicio
- Minnesota Dental Research Center for Biomaterials and Biomechanics, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Moos Health Science Tower, 515 Delaware Street S.E. Minneapolis, MN 55455
| | - Robert S Jones
- Division of Pediatric Dentistry, School of Dentistry, University of Minnesota, Moos Health Science Tower, 515 Delaware Street S.E. Minneapolis, MN 55455
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Multifunctional monomer acts as co-initiator and crosslinker to provide autonomous strengthening with enhanced hydrolytic stability in dental adhesives. Dent Mater 2019; 36:284-295. [PMID: 31806495 DOI: 10.1016/j.dental.2019.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 10/31/2019] [Accepted: 11/15/2019] [Indexed: 12/23/2022]
Abstract
OBJECTIVE The purpose of this study was to evaluate a new synthesized multifunctional monomer, aminosilane functionalized methacrylate (ASMA), containing polymerizable methacrylate, tertiary amine, and methoxysilane functionalities in dental adhesive formulations, and to investigate the polymerization kinetics, leachates, thermal and mechanical properties of copolymers. METHODS Adhesive contained HEMA/BisGMA (45/55, w/w) was used as a control, and mixtures based on HEMA/BisGMA/ASMA at the mass ratio of 45/(55-x)/x were used as experimental adhesive. Adhesives were characterized with regard to water miscibility, photo-polymerization behavior (Fourier transform infrared spectroscopy, FTIR), leached co-monomers (high performance liquid chromatography, HPLC), thermal properties (modulated differential scanning calorimeter, MDSC), and mechanical properties (dynamic mechanical analyzer, DMA). Stress relaxation times and the corresponding moduli, obtained from stress relaxation tests, are used in a simulated linear loading case. RESULTS As compared to the control, ASMA-containing adhesives showed higher water miscibility, lower viscosity, improved monomer-to-polymer conversion, significantly greater Tg and rubbery modulus. HPLC results indicated a substantial reduction of leached HEMA (up to 85wt%) and BisGMA (up to 55wt%) in ethanol. The simulation reveals that the ASMA-containing adhesive becomes substantially stiffer than the control. SIGNIFICANCE ASMA monomer plays multiple roles, i.e. it serves as both a co-initiator and crosslinker while also providing autonomous strengthening and enhanced hydrolytic stability in the adhesive formulations. This multifunctional monomer offers significant promise for improving the durability of the adhesive at the composite/tooth interface.
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Song L, Ye Q, Ge X, Misra A, Tamerler C, Spencer P. New silyl-functionalized BisGMA provides autonomous strengthening without leaching for dental adhesives. Acta Biomater 2019; 83:130-139. [PMID: 30366133 DOI: 10.1016/j.actbio.2018.10.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/30/2018] [Accepted: 10/22/2018] [Indexed: 12/27/2022]
Abstract
Resin-based composite has overtaken dental amalgam as the most popular material for direct restorative dentistry. In spite of this popularity the clinical lifetime of composite restorations is threatened by recurrent decay. Degradation of the adhesive leads to gaps at the composite/tooth interface-bacteria, bacterial by-products and fluids infiltrate the gaps leading to recurrent decay and composite restoration failure. The durability of resin-dentin bonds is a major problem. We address this problem by synthesizing silyl-functionalized BisGMA (e.g., silyl-BisGMA), formulating dental adhesives with the new monomer and determining the physicochemical properties and leaching characteristics of the silyl-BisGMA adhesives. Silyl-BisGMA was synthesized by stoichiometric amounts of BisGMA and 3-isocyanatopropyl trimethoxysilane (IPTMS). The control adhesive was a mixture based on HEMA/BisGMA (45/55, w/w). In the experimental formulations, BisGMA was partially or completely replaced by silyl-BisGMA. Water miscibility, polymerization behavior (Fourier transform infrared spectroscopy, FTIR), thermal property (modulated differential scanning calorimetry, MDSC), mechanical properties in dry and wet conditions (dynamic mechanical analysis, DMA), and leached species (HPLC) were investigated. Data from all tests were submitted to appropriate statistical analysis (α = 0.05). Silyl-BisGMA-containing adhesives exhibited comparable water miscibility, lower viscosities, and significantly improved degree of conversion of CC bond as compared to the control. After 4 weeks aqueous aging, the glass transition temperature and rubbery moduli of the experimental copolymers were significantly greater than the control (p < 0.05). HPLC results indicated a substantial reduction of leached HEMA (up to 99 wt%) and BisGMA (up to 90 wt%). By introducing silyl-functional group, the new BisGMA derivative exhibited potential as a monomer that can lead to dental adhesives with improved mechanical properties and reduced leaching under conditions relevant to the oral environment. STATEMENT OF SIGNIFICANCE: The low-viscosity adhesive that bonds the composite to the tooth (enamel and dentin) is intended to seal and stabilize the composite/tooth interface, but it degrades leading to a breach at the composite/tooth margin. As the most popular crosslinking monomer in adhesives, Bisphenol A-glycerolate dimethacrylate (BisGMA) has limitations, e.g. susceptible to hydrolysis and concomitant property degradation. A methoxysilyl-functionalized BisGMA derivative (silyl-BisGMA) was introduced in this work to respond to these limitations. Our results indicated that by introducing silyl-BisGMA, higher crosslinked networks were obtained without sacrificing the homogeneity, and the leached amount of HEMA was reduced up to 99%. This novel resin offers potential benefits including prolonging the functional lifetime of dental resin materials.
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Mohammad Raei Nayini M, Bastani S, Moradian S, Croutxé-Barghorn C, Allonas X. Manipulating the Surface Structure of Hybrid UV Curable Coatings through Photopolymerization-Induced Phase Separation: Influence of Inorganic Portion and Photoinitiator Content. MACROMOL CHEM PHYS 2017. [DOI: 10.1002/macp.201700377] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Mohsen Mohammad Raei Nayini
- Department of Printing Science and Technology; Institute for Color Science and Technology; Vafamanesh St, Sayad Shirazi North HWY PB: 54-16765 Tehran Iran
| | - Saeed Bastani
- Department of Surface Coatings and Corrosion; Institute for Color Science and Technology; Vafamanesh St, Sayad Shirazi North HWY PB: 54-16765 Tehran Iran
- Center of Excellence for Color Science and Technology; Institute of Color Science and Technology; Vafamanesh St, Sayad Shirazi North HWY PB: 54-16765 Tehran Iran
| | - Siamak Moradian
- Center of Excellence for Color Science and Technology; Institute of Color Science and Technology; Vafamanesh St, Sayad Shirazi North HWY PB: 54-16765 Tehran Iran
| | - Céline Croutxé-Barghorn
- Laboratory of Macromolecular Photochemistry and Engineering; University of Haute Alsace; ENSCMu; 3 rue Alfred Werner 68093 Mulhouse France
| | - Xavier Allonas
- Laboratory of Macromolecular Photochemistry and Engineering; University of Haute Alsace; ENSCMu; 3 rue Alfred Werner 68093 Mulhouse France
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Song L, Ye Q, Ge X, Misra A, Tamerler C, Spencer P. Self-Strengthening Hybrid Dental Adhesive via Visible-light Irradiation Triple Polymerization. RSC Adv 2016; 6:52434-52447. [PMID: 27774144 DOI: 10.1039/c6ra09933e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A self-strengthening methacrylate-based dental adhesive system was developed by introducing an epoxy cyclohexyl trimethoxysilane (TS) which contains both epoxy and methoxysilyl functional groups. The experimental formulation, HEMA/BisGMA/TS (22.5/27.5/50, wt%), was polymerized by visible-light. Real-time Fourier transform infrared spectroscopy (FTIR) was used to investigate in situ the free radical polymerization of methacrylate, ring-opening cationic polymerization of epoxy, and photoacid-induced sol-gel reactions. Among the three simultaneous reactions, the reaction rate of the free radical polymerization was the highest and the hydrolysis/condensation rate was the lowest. With 40s-irradiation, the degrees of conversion of the double bond and epoxy groups at 600 s were 73.2±1.2%, 87.9±2.4%, respectively. Hydrolysis of the methoxysilyl group was initially <5%, and increased gradually to about 50% after 48 h dark storage. Photoacids generated through the visible-light-induced reaction were effective in catalyzing both epoxy ring-opening polymerization and methoxysilyl sol-gel reaction. The mechanical properties of copolymers made with TS concentrations from 5 to 35 wt% were obtained using dynamic mechanical analysis (DMA). In wet conditions, the storage moduli at 70 °C and glass transition temperature were significantly higher than that of the control (p<0.05); these properties increased with TS concentration and storage time. The post reaction of hydrolysis/condensation of alkoxysilane could provide persistent strengthening whether in a neutral or acidic environment and these characteristics could lead to enhanced mechanical properties in the oral environment. The cumulative amount of leached species decreased significantly in the TS-containing copolymers. These results provide valuable information for the development of dental adhesives with reduced leaching of methacrylate monomers and enhanced mechanical properties under the wet, oral environment.
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Affiliation(s)
- Linyong Song
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
| | - Qiang Ye
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
| | - Xueping Ge
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
| | - Anil Misra
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.; University of Kansas, Department of Civil Engineering, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
| | - Candan Tamerler
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.; University of Kansas, Department of Mechanical Engineering, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
| | - Paulette Spencer
- University of Kansas, Bioengineering Research Center, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.; University of Kansas, Department of Mechanical Engineering, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA
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Song L, Ye Q, Ge X, Misra A, Spencer P. Mimicking nature: Self-strengthening properties in a dental adhesive. Acta Biomater 2016; 35:138-52. [PMID: 26883773 DOI: 10.1016/j.actbio.2016.02.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 10/22/2022]
Abstract
Chemical and enzymatic hydrolysis provoke a cascade of events that undermine methacrylate-based adhesives and the bond formed at the tooth/composite interface. Infiltration of noxious agents, e.g. enzymes, bacteria, and so forth, into the spaces created by the defective bond will ultimately lead to failure of the composite restoration. This paper reports a novel, synthetic resin that provides enhanced hydrolytic stability as a result of intrinsic reinforcement of the polymer network. The behavior of this novel resin, which contains γ-methacryloxyproyl trimethoxysilane (MPS) as its Si-based compound, is reminiscent of self-strengthening properties found in nature. The efforts in this paper are focused on two essential aspects: the visible-light irradiation induced (photoacid-induced) sol-gel reaction and the mechanism leading to intrinsic self-strengthening. The FTIR band at 2840cm(-1) corresponding to CH3 symmetric stretch in -Si-O-CH3 was used to evaluate the sol-gel reaction. Results from the real-time FTIR indicated that the newly developed resin showed a limited sol-gel reaction (<5%) during visible-light irradiation, but after 48h dark storage, the reaction was over 65%. The condensation of methoxysilane mainly occurred under wet conditions. The storage moduli and glass transition temperature of the copolymers increased in wet conditions with the increasing MPS content. The cumulative amounts of leached species decreased significantly when the MPS-containing adhesive was used. The results suggest that the polymethacrylate-based network, which formed first as a result of free radical initiated polymerization, retarded the photoacid-induced sol-gel reaction. The sol-gel reaction provided a persistent, intrinsic reinforcement of the polymer network in both neutral and acidic conditions. This behavior led to enhanced mechanical properties of the dental adhesives under conditions that simulate the wet, oral environment. STATEMENT OF SIGNIFICANCE A self-strengthening dental adhesive system was developed through a dual curing process, which involves the free radical photopolymerization followed by slow hydrolysis and condensation (photoacid-induced sol-gel reaction) of alkoxylsilane groups. The concept of "living" photoacid-induced sol-gel reaction with visible-light irradiation was confirmed in the polymer. The sol-gel reaction was retarded by the polymethacrylate network, which was generated first; the network extended the life and retained the activity of silanol groups. The self-strengthening behavior was evaluated by monitoring the mechanical properties of the hybrid copolymers under wet conditions. The present research demonstrates the sol-gel reaction in highly crosslinked network as a potentially powerful strategy to prolong the functional lifetime of engineered biomaterials in wet environments.
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