Dynamic monitoring of refractive index change through photoactive resins (original) (raw)
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Journal of Biomedical Optics, 2007
Light-activated resin-based dental composites are increasingly replacing dental amalgam. However, these materials are limited by inefficient setting reactions as a function of depth that constrain the maximum extent of cure. Insufficient curing can contribute to an overall reduction in biocompatibility of the material. We demonstrate dynamic refractive index measurements of a commercial dental composite throughout cure using spectral domain low coherence interferometry. Our results show a linear relationship between the change in refractive index and polymerization-induced reduction in physical thickness during light-activated curing. This relationship between the optical and physical density demonstrates the potential of this technique as a unique noninvasive tool for measurement of the conversion degree of curing dental composite materials.
Dynamic monitoring of curing photoactive resins: A methods comparison
Dental Materials, 2010
Objective. The aim of this investigation was to determine reaction enthalpy, ion viscosity and curing light transmission changes of unfilled methacrylate-based systems in order to compare methods that monitor photoactive resin polymerization. Methods. Photoinitiator (0.2%, w/v, camphoroquinone), accelerator (0.3%, w/v, amine) and inhibitor (ranging from 0 to 1%, w/v, butylated hydroxytoluene, BHT) were incorporated in an experimental BisGMA/TEGDMA co-monomer mixture (50/50, w/v). The concentration of BHT was varied from 0.00, 0.01, 0.05, 0.10, 0.50 to 1.00% (w/v). Light transmission (LT), reaction enthalpy (UV-differential scanning calorimetry, DSC), and ion viscosity (dielectrical analysis, DEA) were determined during irradiation of the resins (40 s; halogen light curingunit). Statistical analysis was performed using two-way ANOVA followed by post hoc tests (˛= 0.05). Curve fitting and regression calculation were done. Results. There was no significant change in the time to reach the maximum rate of polymerization (reaction time) in the individual systems up to a BHT concentration of 0.05% (P > 0.05). Starting at a concentration of 0.10% BHT an increase in time of reaction could be found from 4.0 s (LT), 4.07 s (DEA) and 4.9 s (DSC) to a maximum of 7.4 s (DSC), 9.43 s (DEA) and 9.67 s (LT). Linear increase (y = 5.588 × x) in time to the maximum speed of reaction could be found with a correlation of R 2 = 0.992. Conclusions. The speed of polymerization reaction is strongly influenced by BHT concentration. The linear relationship should allow for the prediction of the speed of reaction during blending of a methacrylate-based resin. The three test systems allow for monitoring the complex polymerization kinetics of unfilled methacrylate-based systems.
Refractive index evolution of various commercial acrylic resins during photopolymerization
Express Polymer Letters, 2018
A set of commercial (meth)acrylic resins was photopolymerized under identical irradiation conditions and evolution of their refractive index was monitored as a function of double bond conversion. Initial refractive index values ranged from 1.4445 to 1.5454 and then linearly increased with conversion as long as the material was not in the glassy state. This increase was related to an increase of the material density arising during polymerization. Final refractive index values ranged from 1.4804 to 1.5632. The knowledge of the refractive index and of its evolution during the photocuring is indispensable, in particularly to elaborate composite materials (polymer matrix + filler) with well controlled optical properties.
Dental materials : official publication of the Academy of Dental Materials, 2002
A novel laser interferometric method for monitoring linear polymerization shrinkage in dental restoratives is demonstrated. The experimental apparatus consists of a low power Helium-Neon laser, a home-built Michelson interferometer, amplified photodiode detectors, and a computer data acquisition system. The feasibility of using interferometry to measure linear shrinkage was evaluated by measuring the percent linear contraction in five commercially available light cured restorative systems. Five-min interferometric curing profiles were collected for each restorative using a 400 mW/cm2 curing light irradiance. The 'interferograms' were converted into percent linear contraction profiles that revealed the relative kinetics of material shrinkage. The overall percent linear contraction after 5 min compares favorably with literature data for the five commercial restoratives studied here. Interferometry offers several advantages over conventional methods of measuring polymerization ...
Dynamic cure measurement of dental polymer composites using optical coherence tomography
Lasers in Dentistry XIV, 2008
Dental amalgam is being increasingly replaced by Light-activated resin-based dental composites. However, these materials are limited by inefficient setting reactions as a function of depth, constraining the maximum extent of cure and reducing biocompatibility. In this paper we demonstrate a novel metrological tool for dynamic monitoring of refractive index and thickness change through curing resins using spectral-domain optical coherence tomography. We present real-time measurements from pre-to post-cure of a series of un-filled bisphenol-A diglycidyl ether dimethacrylate (bisGMA) and triethylene glycol dimethacrylate (TEGDMA) resins with different inhibitor concentrations. Our results demonstrate that refractive index measurements are sensitive to the extent of cure of such resins and that the inhibitor concentration strongly affects the cure dynamics and final extent of cure.
A Practical Fiber Optic Sensor to Monitor Resin Cure and Interphase Formation (583)
A fluorescent probe, covalently grafted to glass, is used to study the glass / resin interphase region near the surface. A shift in the fluorescence maximum during resin cure can be monitored when the grafted dye is immersed in epoxy. The position of the fluorescence maximum is used to detect a difference between the bulk resin and interphase. To make the technique practical as a cure sensor, the dye can be grafted to a glass fiber optic.
Optics Communications, 2007
A fiber optic sensing method based on a Fizeau-type interferometric scheme was employed for monitoring linear polymerization shrinkage in dental restoratives. This technique offers several advantages over the conventional methods of measuring polymerization contraction. This simple, compact, non-invasive and self-calibrating system competes with both conventional and other high-resolution bulk interferometric techniques. In this work, an analysis of the quality of interference signal and fringes visibility was performed in order to characterize their resolution and application range. The measurements of percent linear contraction as a function of the sample thickness were carried out in this study on two dental composites: Filtek P60 (3M ESPE) Posterior Restorer and Filtek Z250 (3M ESPE) Universal Restorer. The results were discussed with respect to others obtained employing alternative techniques.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2015
This study correlated the refractive indices (RIs) of unfilled resin mixtures and resin-based composites (RBCs) with color and translucency of conventional and low-shrinkage RBCs. Unfilled resin mixtures based on different ratios of conventional monomers Bisphenol A-glycidyl-methacrylate (BisGMA)/triethyleneglycol-dimethacrylate (TEGDMA) and urethane-dimethacrylate (UDMA)/TEGDMA and a low-shrinkage monomer FIT-852 (FIT, Esstech Inc.)/TEGDMA were used to prepare model RBCs, containing 30 wt % of the organic matrix and 70 wt % of silanated barium-glass fillers (n 5 1.553, Esstech Inc.). The RIs of resins were measured on an ABBE refractometer, those of cured RBCs using the Becke-line method in immersion oils. Color and translucency were determined using an AvaSpec-2048 (Avantes BV) spectrometer. The RIs of unfilled resin mixtures decreased with increasing amounts of TEGDMA. Cured RBCs had higher RIs than their respective resin mixtures. BisGMA-based composites were more translucent with significantly lower L* values than FIT-and UDMA-based RBCs. The RIs of unfilled resins positively correlated with cured RBCs (p 5 0.001), as did the RIs with translucency (p 5 0.001) and color (p 5 0.008). Resin mixtures and corresponding RBCs based on UDMA and its modified low-shrinkage version, FIT, showed similar optical properties. The RIs of unfilled resins appeared to be good predictors of the RIs of cured RBCs. V C 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2015. How to cite this article: Miletic V, Jakovljevic N, Manojlovic D, Marjanovic J, Rosic AA, Dramicanin MD. 2015. Refractive indices of unfilled resin mixtures and cured composites related to color and translucency of conventional and low-shrinkage composites. J Biomed Mater Res Part B 2015:00B:000-000. V C 2015 WILEY PERIODICALS, INC.