Papers by Keyword: Degree of Conversion

Abstract: In this work, urethane dimethacrylate (UDMA) was used as dental resin as an non-toxic alternative to Bisphenol A-glycidyl methacrylate (Bis-GMA). Additionally, UDMA combine with triethylene glycol dimethacrylate (TEGDMA) monomer with various concentration ratio, meanwhile camphorquinone (CQ) and diphenyl-(2,4,6-trimethylbenzoyl) phosphine (TPO) as photoinitiator. First, UDMA:TEGDMA with ratio of 40:60, 50:50, 60:40, 70:30 and 80:20 wt.% was prepared. Second, the solution was ultrasonic for 15 min with introduction of CQ and TPO (1:2 wt%). Third, irradiation of UV LED with wavelength of 375 nm for 2 min to initiate polymerization reaction of monomers. Scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA) and mechanical properties were used to investigate the morphology, chemical bonding of polymerization reaction, decomposition temperature and tensile strength. Based on our findings, we found that that UDMA:TEGDMA ratio of 50:50 wt% demonstrates uniform and smooth surface, high degree of conversion, and good mechanical strength, which is promising for dental resin.

Abstract: The search for optimal conditions for the method of synthesis of copper (II) salts to create a unified one-step method for obtaining salts from natural raw materials was the purpose of this work. During the process of salt production, it is desirable that the product accumulates in the solid phase and is easily separated by phase separation methods. The study of the direct interaction of copper (II) oxide with acids in organic liquid media using a bead mill as a reactor and grinding agent of different nature showed that besides the usual places of localization of product that take place in practice, we can meet unusual places of localization of product, such as the surface of a foreign solid phase in the reactor zone, for example, the surface of the grinding agent, reactor elements, etc. It was found that in some cases, localization on a solid surface could be a favorable localization option in terms of the speed of the process. But it happens not always, because it requires specific methods of separation of film from surface, which can be very expensive. Often, the localization of the product on the solid surfaces is an extremely unfavorable localization option. It was found that different variants of product localization of interaction CuO with acids which were implemented in different proportions, prevented the creation of a unified method for producing salts in such systems

Abstract: The objectives of this study were to compare the polymerization of three experimental light-cured orthodontic adhesives by determining their degree of conversion (DOC) and to compare the results with a control (Transbond XT; 3M Unitek, USA). Three formulas of an in-house orthodontic adhesive were divided according to monomer ratio (BisGMA:TEGDMA) into group 1 (8:2), 2 (7:3), and 3 (6:4), respectively, with 60-70 weight % of filler amount and 0.5 % of photoinitiator (TPO). All specimen (n=5 per group) were cured with a LED curing unit. The DOC was estimated using Fourier transform infrared (FTIR) spectrometer (Nicolet 6700, Madison, Michigan, USA) immediately following polymerization and on Day 1, Day 7, and Day 30. For statistical analysis, Kruskal-Wallis and Friedman tests were used to compare the materials and the periods, respectively, with p=0.05. The result showed that the DOC was significantly different among the groups and time periods. The highest and lowest DOC at each of the periods were obtained from group 3 and group 1, respectively. Among the time periods, the DOC values of all groups increased considerably on Day 1 following curing as compared to when it was measured immediately, and the DOC gradually increased until Day 30. In conclusion, the experimental orthodontic adhesive in group 3 with a monomer ratio of 6:4 provided the highest DOC among all the adhesives and was superior to Transbond XT at all periods of examination.

Abstract: Introduction: The aim of this in-vitro study was to analyze the polymerization ability of 3 light-cured orthodontic adhesives by determining the degree of conversion (DC). Materials and Methods: Fourier transform infrared spectroscopy (FTIR) was used to evaluate the DC after polymerization immediately, 1 day, 7 days, and 30 days. The adhesives investigated were Transbond XT (3M Unitek, USA), Grengloo (Ormco Corp., USA), and Green Glue (Hangzhou Biomaterials, China). Twelve stainless steel brackets (n=4) were used and the adhesives were cured with Bluephase G2 (Ivoclar Vivadent, Liechtenstein). The data were analyzed by Kruskal-Wallis test for comparing materials and Friedman test for comparing the time periods. Results: The DC values were significantly different among the materials and among the time periods. The highest DC in each period was obtained for Grengloo and the lowest DC was observed for Transbond XT. Thus, there were significant differences between the DC values of Grengloo and Transbond XT in each period. Among the time periods, DC% at T1 (Immediately) and T3 of the material were significantly different. The DC values of all adhesives increased extremely from immediately following curing to 1 day and then slightly increased from 1 day to 7 days. Conclusions: Grengloo showed the highest levels of DC at all tested periods. The percentage values of DC largely increased from immediately following curing to 1 day. This concluded that monomers in orthodontic adhesives kept converting even after completion of photoactivation.

Abstract: The composite, based on a polymer matrix such as Bisphenol A glycol dimethacrylate (Bis-GMA), urethane dimethacrylate (UDMA), and triethyleneglycoldimethacrylate (TEGDMA) and a reinforced-ceramic filler has been used in dental restorative materials. The light curing composite consists of Bis-GMA, TEGDMA, UDMA, Bis-GMA/TEGDMA, Bis-GMA/UDMA, or UDMA/TEGDMA polymer systems and a fumed silica filler with 35 weight ratio loading was synthesized using camphorquinone (CQ) and 2-(dimet6hyloamino)ethyl methacrylate (DMAEMA) as an initiator system. FTIR spectroscopy was used to determine the degree of conversion (DC) of the composites. Polymerization shrinkage and physical properties such as hardness strength and flexural strength were correlated with the composites containing different polymer systems.