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Title
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Fate of resin-based materials in dental restorations : identification of monomers and degradation products from resin-based dental materials in vitro and in vivo
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Author
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Abstract
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| Since 2011, the World Health Organization has encouraged a global phase-down of the use of dental amalgam and actively supported the use of alternative, resin-based dental materials. Resin-based dental materials usually consist of a mixture of inorganic filler particles attached to a resin matrix. The organic resin-based matrix consists most commonly of (meth)acrylate monomers and functional additives (photo- and co-initiators, stabilizers and others). Upon restoration, the resin-based materials need to be cured by polymerization of the resin matrix, but this process is not complete, resulting in the release of chemicals after restorative treatments. This thesis aimed to answer three important questions regarding resin-based dental materials: 1. What are the ingredients of dental composites and sealants? 2. To which chemicals are patients possibly exposed during and after dental restoration surgery? 3. To what extent are dental composites degraded after restoration, and which degradation products do they release? The composition of resin-based dental materials was investigated using liquid chromatography coupled to high-resolution mass spectrometry. Major components, such as the monomers BisEMA, BisGMA, TEGDMA and UDMA, were identified although they were not always stated in the MSDSs. Minor components included photoinitiators, such as ethyl 4-dimethyl aminobenzoate (EDMAB) and (meth)acrylate impurities originating from production of main ingredients. Unreacted monomers and not covalently bound additives can leach out of the polymer matrix after restorative treatment, a process which can be aggravated by degradation of the polymer due to exposure to various stressors in the mouth, such as pH and enzymes in saliva. To test this hypothesis, dental monomers and polymerized dental resin-based materials were immersed for 24 h in chemical media and human pooled saliva in order to identify leached monomers and degradation products. During in vitro chemical degradation, uncured monomers were rapidly hydrolyzed to mono- and demethacrylated degradation products. Degradation in human pooled saliva for 24 h to mimic the in vivo situation, resulted in the identification of both monomers and their degradation products. The liver metabolism of leached monomers was simulated using an in-house assay using human liver microsomes and human liver cytosols. During Phase I incubation the (meth)acrylic acid in the monomers was rapidly removed followed by oxidative and hydroxylation pathways. For BisPMA, an O-dealkylation pathway resulted in the formation of BPA. Carbamate groups present in TCD-DI-HEA and UDMA were resistant to biotransformation reactions. Phase II biotransformation products were only observed for BisPMA and included conjugation reactions with sulphate and glucuronic acid. In the final part of the thesis, a study was carried out for the first time aiming to quantitatively and qualitatively monitor the release of parent compounds and their degradation products in saliva from patients undergoing multiple restorations. Saliva samples were collected at various time points after restorative treatment. Monomers are only present in saliva shortly after restoration, but several degradation products can be detected weeks after the restoration confirming a long-term release. Results from this thesis show that patients may be exposed to monomers and their degradation products after restorative surgery, for which little to no toxicological data exists. If possible, it can be considered to limit the number of teeth treated per session and to plan multiple restorations with several weeks in between in order to limit exposure to chemicals from resin-based dental materials. |
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Language
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English
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Publication
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Antwerpen
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Universiteit Antwerpen, Faculteit Farmaceutische, Biomedische en Diergeneeskundige Wetenschappen, Departement Farmaceutische Wetenschappen
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2021
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Volume/pages
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206 p.
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Note
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Covaci, Adrian [Supervisor]
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Landuyt, Van, Kirsten L. [Supervisor]
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Full text (open access)
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