Refractive indices of unfilled resin mixtures and cured composites related to color and translucency of conventional and low‐shrinkage composites

Abstract

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 = 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 = 0.001), as did the RIs with translucency (p = 0.001) and color (p = 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. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 7-13, 2017.

Translucency and color stability of resin composite and dental adhesives as modeling liquids – A one-year evaluation

“…In the present work, refractive index mismatches between the modeling liquid (unfilled resin) and composite (highly filled resin) may be expected to affect the way light is transmitted within materials containing the former, 13,14,15 thereby changing the translucency and opacity of the resulting composites. This expectation was confirmed at baseline, in which specimens containing SBMP or SB showed 29%-60% higher TP than the control, (Figures 1a, 1b).…”

Effect of UV aging on translucency of currently used esthetic CAD‐CAM materials

“…In this study, the specimens were obtained using a low speed cutting device and a diamond blade; so it was possible to slice specimens with fairly smooth and homogeneous surface. As described before, the reflectance values of the backings will affect the calculated or observed colors, as the color of the backing and the optical continuity between the translucent material and the backing each affect the color of the translucent material on that backing . As the optical continuity could be also achieved by using optical liquids or glycerin; some studies did not use these materials as they prepared the specimens flat .…”

Optical properties of composite restorations influenced by dissimilar dentin restoratives

“…The choice of shades is not always easy, considering that color of the composite changes after polymerization [11][12][13][14]. This change is affected by the initiator system [14,15] as well as the change in the refractive indices of the polymer relative to the fillers [16,17]. Furthermore, a number of factors may cause long-term color change, such as dehydration, chemical degradation, leakage, poor bonding and increased, surface roughness [18].…”