Sri Vikram Palagummi1, Taeseung Hong2, Zhengzhi Wang3, Chang Kwon Moon4, Martin Y M Chiang5. 1. Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD, United States. 2. Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD, United States; Department of Materials Science and Engineering, Pukyong National University, Busan, Republic of Korea. 3. Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan, Hubei, China. 4. Department of Materials Science and Engineering, Pukyong National University, Busan, Republic of Korea. 5. Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD, United States. Electronic address: martin.chiang@nist.gov.
Abstract
OBJECTIVE: To provide conditions for the validity of the exposure reciprocity law as it pertains to the photopolymerization of dimethacrylate-based dental composites. METHODS: Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMA and UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the composites used camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system. A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and a microprobe thermocouple was used to simultaneously measure the degree of conversion (DC), the polymerization stress (PS) due to the shrinkage, and the temperature change (TC) in real time during the photocuring process. The instrument has an integrated LED light curing unit providing irradiances ranging from 0.01W/cm2 to 4W/cm2 at a peak wavelength of 460nm (blue light). Vickers hardness of the composites was also measured. RESULTS: For every dental composite there exists a minimum radiant exposure required for an adequate polymerization (i.e., insignificant increase in polymerization with any further increase in the radiant exposure). This minimum predominantly depends on the resin viscosity of composite and can be predicted using an empirical equation established based on the test results. If the radiant exposure is above this minimum, the exposure reciprocity law is valid with respect to DC for high-fill composites (filler contents >50% by mass) while invalid for low-fill composites (that are clinically irrelevant). SIGNIFICANCE: The study promotes better understanding on the applicability of the exposure reciprocity law for dental composites. It also provides a guidance for altering the radiant exposure, with the clinically available curing light unit, needed to adequately cure the dental composite in question. Published by Elsevier Inc.
OBJECTIVE: To provide conditions for the validity of the exposure reciprocity law as it pertains to the photopolymerization of dimethacrylate-based dental composites. METHODS: Composites made from different mass ratios of resin blends (Bis-GMA/TEGDMA and UDMA/TEGDMA) and silanized micro-sized glass fillers were used. All the composites used camphorquinone and ethyl 4-dimethylaminobenzoate as the photo initiator system. A cantilever beam-based instrument (NIST SRI 6005) coupled with NIR spectroscopy and a microprobe thermocouple was used to simultaneously measure the degree of conversion (DC), the polymerization stress (PS) due to the shrinkage, and the temperature change (TC) in real time during the photocuring process. The instrument has an integrated LED light curing unit providing irradiances ranging from 0.01W/cm2 to 4W/cm2 at a peak wavelength of 460nm (blue light). Vickers hardness of the composites was also measured. RESULTS: For every dental composite there exists a minimum radiant exposure required for an adequate polymerization (i.e., insignificant increase in polymerization with any further increase in the radiant exposure). This minimum predominantly depends on the resin viscosity of composite and can be predicted using an empirical equation established based on the test results. If the radiant exposure is above this minimum, the exposure reciprocity law is valid with respect to DC for high-fill composites (filler contents >50% by mass) while invalid for low-fill composites (that are clinically irrelevant). SIGNIFICANCE: The study promotes better understanding on the applicability of the exposure reciprocity law for dental composites. It also provides a guidance for altering the radiant exposure, with the clinically available curing light unit, needed to adequately cure the dental composite in question. Published by Elsevier Inc.
Authors: Sébastien Beun; Christian Bailly; Anne Dabin; José Vreven; Jacques Devaux; Gaëtane Leloup Journal: Dent Mater Date: 2008-07-14 Impact factor: 5.304
Authors: Aurealice Rosa Maria Martins; Luciana Machado-Santos; Regis Cleo Fernandes Grassia; Rafael Pino Vitti; Mário Alexandre Coelho Sinhoreti; William Cunha Brandt Journal: Eur J Dent Date: 2021-01-07