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Dzwonkowska-Zarzycka M, Sionkowska A. Photoinitiators for Medical Applications-The Latest Advances. Molecules 2024; 29:3898. [PMID: 39202977 PMCID: PMC11357272 DOI: 10.3390/molecules29163898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Revised: 08/05/2024] [Accepted: 08/11/2024] [Indexed: 09/03/2024] Open
Abstract
Photopolymerization is becoming increasingly popular in industry due to its copious advantages. The vital factor in the entire pre-polymerization formulation is the presence of photoinitiators. Depending on the application, photoinitiators have different features. Hence, scientists are particularly interested in developing new photoinitiators that can expand the scope of applications and be used to create products with the features demanded by current trends. This brief review summarizes the photoinitiators used in dental materials and hydrogels and those obtained from natural and synthetic sources.
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Affiliation(s)
- Monika Dzwonkowska-Zarzycka
- Department of Organic Chemistry, Faculty of Chemical Technology and Engineering, Bydgoszcz University of Science and Technology, Seminaryjna 3, 85-326 Bydgoszcz, Poland
| | - Alina Sionkowska
- Department of Biomaterials and Cosmetic Chemistry, Faculty of Chemistry, Nicolaus Copernicus University in Torun, Gagarina 7 Street, 87-100 Torun, Poland
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Fayad BR, Zohdy MM, Hussein GA, Farag EA. Color stability and marginal adaptation of ceramic veneers cemented using different composite resins. Minerva Dent Oral Sci 2024; 73:88-95. [PMID: 37066892 DOI: 10.23736/s2724-6329.23.04761-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
BACKGROUND The purpose of this study was to compare the color stability and marginal adaption of lithium disilicate veneers before and after thermocycling using various resin composite materials employed as cement. METHODS Laminate veneer preparation was done on an acrylic tooth according to standardized procedures. The veneer preparations were duplicated into twenty-one dies. The veneers were fabricated from lithium disilicate using the CEREC in Lab system. According to the cement type, the twenty-one die specimens were randomly divided into three equal groups: group I, with light cured adhesive resin cement (N.=7), group II, with flowable light cured composite, and group III, with preheated nano filled composite. The cemented specimens underwent 5000 thermocycling cycles. Color was assessed using a reflective spectrophotometer. The vertical marginal gap, following cementation and thermocycling, was measured using a digital microscope. One-way ANOVA followed by Tukey's post-hoc test was used to statistically assess the data. RESULTS After thermocycling, there was no statistically significant difference in ΔE among cement type groups for color stability (P=0.369). However, the preheated composite showed the lowest ΔE mean values. Within adhesive resin cement and flowable composite groups, marginal gap means values recorded after thermocycling were significantly higher than those after cementation (P=0.013 and P<0.001, respectively). CONCLUSIONS Although preheated composite cement showed the highest marginal discrepancy, it would be the best choice regarding color stability.
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Affiliation(s)
- Basma R Fayad
- Department of Fixed Prosthodontics, British University, Cairo, Egypt -
| | - Maged M Zohdy
- Department of Fixed Prosthodontics, British University, Cairo, Egypt
- Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
| | - Ghada A Hussein
- Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
| | - Engy A Farag
- Department of Fixed Prosthodontics, British University, Cairo, Egypt
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Yudin VV, Shurygina MP, Egorikhina MN, Aleynik DY, Linkova DD, Charykova IN, Kovylin RS, Chesnokov SA. Pore Structure Tuning of Poly-EGDMA Biomedical Material by Varying the O-Quinone Photoinitiator. Polymers (Basel) 2023; 15:polym15112558. [PMID: 37299356 DOI: 10.3390/polym15112558] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/12/2023] Open
Abstract
Porous polymer monoliths with thicknesses of 2 and 4 mm were obtained via polymerization of ethylene glycol dimethacrylate (EGDMA) under the influence visible-light irradiation in the presence of a 70 wt% 1-butanol porogenic agent and o-quinone photoinitiators. The o-quinones used were: 3,5-di-tret-butyl-benzoquinone-1,2 (35Q), 3,6-di-tret-butyl-benzoquinone-1,2 (36Q), camphorquinone (CQ), and 9,10-phenanthrenequinone (PQ). Porous monoliths were also synthesized from the same mixture but using 2,2'-azo-bis(iso-butyronitrile) (AIBN) at 100 °C instead o-quinones. According to the results of scanning electron microscopy, all the resulting samples were conglomerates of spherical, polymeric particles with pores between them. Use of mercury porometry showed that the interconnected pore systems of all the polymers were open. The average pore size, Dmod, in such polymers strongly depended on both the nature of the initiator and the method of initiation of polymerization. For polymers obtained in the presence of AIBN, the Dmod value was as low as 0.8 μm. For polymers obtained via photoinitiation in the presence of 36Q, 35Q, CQ, and PQ, the Dmod values were significantly greater, i.e., 9.9, 6.4, 3.6, and 3.7 μm, respectively. The compressive strength and Young's modulus of the porous monoliths increased symbatically in the series PQ < CQ < 36Q < 35Q < AIBN with decreasing proportions of large pores (over 12 μm) in their polymer structures. The photopolymerization rate of the EGDMA and 1-butanol, 30:70 wt% mixture was maximal for PQ and minimal for 35Q. All polymers tested were non-cytotoxic. Based on the data from MTT testing, it can be noted that the polymers obtained via photoinitiation were characterized by their positive effect on the proliferative activity of human dermal fibroblasts. This makes them promising osteoplastic materials for clinical trials.
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Affiliation(s)
- Vladimir V Yudin
- G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, 49 Tropinina, 603950 Nizhny Novgorod, Russia
| | - Margarita P Shurygina
- G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, 49 Tropinina, 603950 Nizhny Novgorod, Russia
| | - Marfa N Egorikhina
- Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University of the Ministry of Health of the Russian Federation, 10/1 Ploshchad Minina i Pozharskogo, 603005 Nizhny Novgorod, Russia
| | - Diana Ya Aleynik
- Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University of the Ministry of Health of the Russian Federation, 10/1 Ploshchad Minina i Pozharskogo, 603005 Nizhny Novgorod, Russia
| | - Daria D Linkova
- Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University of the Ministry of Health of the Russian Federation, 10/1 Ploshchad Minina i Pozharskogo, 603005 Nizhny Novgorod, Russia
| | - Irina N Charykova
- Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University of the Ministry of Health of the Russian Federation, 10/1 Ploshchad Minina i Pozharskogo, 603005 Nizhny Novgorod, Russia
| | - Roman S Kovylin
- G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, 49 Tropinina, 603950 Nizhny Novgorod, Russia
| | - Sergey A Chesnokov
- G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, 49 Tropinina, 603950 Nizhny Novgorod, Russia
- Federal State Budgetary Educational Institution of Higher Education, Privolzhsky Research Medical University of the Ministry of Health of the Russian Federation, 10/1 Ploshchad Minina i Pozharskogo, 603005 Nizhny Novgorod, Russia
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Overviews on the Progress of Flowable Dental Polymeric Composites: Their Composition, Polymerization Process, Flowability and Radiopacity Aspects. Polymers (Basel) 2022; 14:polym14194182. [PMID: 36236127 PMCID: PMC9570751 DOI: 10.3390/polym14194182] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/06/2022] [Accepted: 10/01/2022] [Indexed: 11/17/2022] Open
Abstract
A review article has been conducted including the main research results and comments referring to flowable dental polymeric materials. To begin with, the synthesis and composition of this category of composites is discussed, revealing the major components of the commercial products in terms of chemistry and proportion. Later, the polymerization characteristics are unfolded regarding the reaction time and rate, volumetric shrinkage and depth of cure for both photocurable and self-curable composites. To continue, some perspectives of the pre-treatment or accompanying processes that a clinician may follow to enhance the materials' performance are described. Fluidity is certainly associated with the progress of polymerization and the in-depth conversion of monomers to a polymeric network. Last, the aspects of radiopacity and translucency are commented on, showing that all flowable polymeric composites satisfy the radiography rule, while the masking ability depends on the fillers' properties and specimen thickness. The reviewing article is addressed to all field scientists and practitioners dealing with flowable dental composites studies or applications.
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Can TPO as Photoinitiator Replace "Golden Mean" Camphorquinone and Tertiary Amines in Dental Composites? Testing Experimental Composites Containing Different Concentration of Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide. Int J Mol Sci 2022; 23:ijms231911594. [PMID: 36232894 PMCID: PMC9569800 DOI: 10.3390/ijms231911594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/21/2022] [Accepted: 09/26/2022] [Indexed: 11/25/2022] Open
Abstract
The aim of this research was to compare the biomechanical properties of experimental composites containing a classic photoinitiating system (camphorquinone and 2-(dimethylami-no)ethyl methacrylate) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator. The produced light-cured composites consisted of an organic matrix-Bis-GMA (60 wt.%), TEGDMA (40 wt.%) and silanized silica filler (45 wt.%). Composites contained 0.27; 0.5; 0.75 or 1 wt.% TPO. Vickers hardness, microhardness (in the nanoindentation test), diametral tensile strength, resistance to three-point bending and the CIE L* a* b* colorimetric analysis was performed with each composite produced. The highest average Vickers hardness values were obtained for the composite containing 1 wt.% TPO (43.18 ± 1.7HV). The diametral tensile strength remains on regardless of the type and amount of photoinitiator statistically the same level, except for the composite containing 0.5 wt.% TPO for which DTS = 22.70 ± 4.7 MPa and is the lowest recorded value. The highest average diametral tensile strength was obtained for the composite containing 0.75 wt.% TPO (29.73 ± 4.8 MPa). The highest modulus of elasticity characterized the composite containing 0.75 wt.% TPO (5383.33 ± 1067.1 MPa). Composite containing 0.75 wt.% TPO has optimal results in terms of Vickers hardness, diametral tensile strength, flexural strength and modulus of elasticity. Moreover, these results are better than the parameters characterizing the composite containing the CQ/DMAEMA system. In terms of an aesthetic composite containing 0.75 wt.%. TPO is less yellow in color than the composite containing CQ/DMAEMA. This conclusion was objectively confirmed by test CIE L* a* b*.
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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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Zhang X, Zhang Q, Meng X, Ye Y, Feng D, Xue J, Wang H, Huang H, Wang M, Wang J. Rheological and Mechanical Properties of Resin-Based Materials Applied in Dental Restorations. Polymers (Basel) 2021; 13:2975. [PMID: 34503014 PMCID: PMC8433687 DOI: 10.3390/polym13172975] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 08/28/2021] [Accepted: 08/28/2021] [Indexed: 11/26/2022] Open
Abstract
Resin-based materials have been prevalent for dental restorations over the past few decades and have been widely used for a variety of direct and indirect procedures. Typically, resin-based dental materials are required to be flowable or moldable before setting and can provide adequate mechanical strength after setting. The setting method may include, but is not limited to, light-curing, self-curing or heating. In this review, based on different indications of resin-based dental materials (e.g., dental filling composite, dental bonding agent, resin luting cement), their rheological and mechanical properties were reviewed. Viscous and flexible properties were focused on for materials before setting, while elastic properties and mechanical strength were focused on for materials after setting. At the same time, the factors that may affect their rheological and mechanical properties were discussed. It is anticipated that the insightful information and prospections of this study will be useful to the future development and fabrication of resin-based dental restorative materials.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Jing Wang
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 Xincun Rd., Zibo 255000, China; (X.Z.); (Q.Z.); (X.M.); (Y.Y.); (D.F.); (J.X.); (H.W.); (H.H.); (M.W.)
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Lara L, Rocha MG, de Menezes LR, Correr AB, Sinhoreti MAC, Oliveira D. Effect of combining photoinitiators on cure efficiency of dental resin-based composites. J Appl Oral Sci 2021; 29:e20200467. [PMID: 34320117 PMCID: PMC8315791 DOI: 10.1590/1678-7757-2020-0467] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 03/06/2021] [Accepted: 04/05/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Camphorquinone is the most conventionally used photoinitiator in Dentistry. Although different alternative photoinitiators have been proposed, no photoinitiator was capable of completely substituting camphorquinone. The combination of photoinitiators has been considered the best alternative. OBJECTIVES To evaluate the effect of combining Norrish type I and II photoinitiators on the cure efficiency of dental resin-based composites. METHODOLOGY Experimental composites were produced containing different photoinitiator systems: Norrish type I-only, mono-alkyl phosphine oxide (TPO); Norrish type II-only, camphorquinone (CQ); or its combination, CQ and TPO, in a 1: 1 molar ratio. UV-vis absorption spectrophotometry was performed to assess the consumption of each photoinitiator after curing (n=3). A multi-wave LED (Bluephase® G2, Ivoclar Vivadent) was pre-characterized and used with a radiant exposure of 24 J/cm2. The degree of conversion was evaluated by Raman spectrometry, and the elution of the monomers by nuclear magnetic resonance analysis (n=3). Data were analyzed using ANOVA and Tukey's test (α=0.05; β=0.2). RESULTS The combination of CQ and TPO increased the consumption of the photoinitiator system compared to CQ-only (p=0.001), but presented similar consumption compared to TPO-only (p=0.52). There was no significant difference in the degree of conversion between the composites regardless of the photoinitiator system (p=0.81). However, the elution of the monomers was reduced when both photoinitiators were combined. TPO-based material presented the highest elution of monomers. CONCLUSIONS The combination of the photoinitiator systems seems to be beneficial for the cure efficiency of dental resin-based composites.
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Affiliation(s)
- Lucas Lara
- Universidade Estadual de Campinas – UNICAMPFaculdade de Odontologia de PiracicabaDepartamento de Odontologia RestauradoraPiracicabaSPBrasilUniversidade Estadual de Campinas – UNICAMP, Faculdade de Odontologia de Piracicaba, Departamento de Odontologia Restauradora, Piracicaba, SP, Brasil.
| | - Mateus Garcia Rocha
- Universidade Federal do Rio de JaneiroInstituto de Macromoléculas Professora Eloisa ManoRio de JaneiroRJBrasilUniversidade Federal do Rio de Janeiro, Instituto de Macromoléculas Professora Eloisa Mano, Rio de Janeiro, RJ, Brasil.
| | - Livia Rodrigues de Menezes
- Universidade Federal do Rio de JaneiroInstituto de Macromoléculas Professora Eloisa ManoRio de JaneiroRJBrasilUniversidade Federal do Rio de Janeiro, Instituto de Macromoléculas Professora Eloisa Mano, Rio de Janeiro, RJ, Brasil.
| | - Américo Bortolazzo Correr
- Universidade Estadual de Campinas – UNICAMPFaculdade de Odontologia de PiracicabaDepartamento de Odontologia RestauradoraPiracicabaSPBrasilUniversidade Estadual de Campinas – UNICAMP, Faculdade de Odontologia de Piracicaba, Departamento de Odontologia Restauradora, Piracicaba, SP, Brasil.
| | - Mario Alexandre Coelho Sinhoreti
- Universidade Estadual de Campinas – UNICAMPFaculdade de Odontologia de PiracicabaDepartamento de Odontologia RestauradoraPiracicabaSPBrasilUniversidade Estadual de Campinas – UNICAMP, Faculdade de Odontologia de Piracicaba, Departamento de Odontologia Restauradora, Piracicaba, SP, Brasil.
| | - Dayane Oliveira
- University of FloridaDivision of Operative DentistryDepartment of Restorative Dental SciencesGainesvilleFLUnited StatesUniversity of Florida, Division of Operative Dentistry, Department of Restorative Dental Sciences, Gainesville, FL, United States.
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The Photoinitiators Used in Resin Based Dental Composite-A Review and Future Perspectives. Polymers (Basel) 2021; 13:polym13030470. [PMID: 33540697 PMCID: PMC7867280 DOI: 10.3390/polym13030470] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 01/27/2021] [Accepted: 01/29/2021] [Indexed: 11/26/2022] Open
Abstract
The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin.
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Misinterpretation of ISO 4049 standard recommendations: Impact on Young's modulus and conversion degree of dental composites. J Mech Behav Biomed Mater 2020; 110:103947. [DOI: 10.1016/j.jmbbm.2020.103947] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 06/16/2020] [Accepted: 06/21/2020] [Indexed: 11/19/2022]
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A blue to red light sensitive photoinitiating systems based on 3,5-di-tert-butyl-o-benzoquinone derivatives for free radical polymerization. Eur Polym J 2020. [DOI: 10.1016/j.eurpolymj.2020.109573] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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A Combined Approach for the Aesthetic Management of Stained Enamel Opacities: External Bleaching Followed by Resin Infiltration. Case Rep Dent 2018; 2018:1605842. [PMID: 30116645 PMCID: PMC6079618 DOI: 10.1155/2018/1605842] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 05/11/2018] [Accepted: 06/19/2018] [Indexed: 11/18/2022] Open
Abstract
Stained enamel opacities are frequently encountered in dental practice. However, due to the risk of unaesthetic outcome, managing such lesions by resin infiltration techniques alone is not advised. Therefore, performing external bleaching before resin infiltration procedure is mandatory to eliminate stains from the hypomineralized lesions in order to aesthetically infiltrate them. In this work, we describe clinical cases in which external bleaching and resin infiltration techniques were used for managing stained enamel hypomineralized lesions related to traumatic dental injuries and molar incisor hypomineralization. Despite the fact that this approach has some limitations, it could be concluded that external bleaching associated with the resin infiltration technique shows promising results to aesthetically manage stained enamel opacities when the stain is totally removed after bleaching.
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