In this work the color dependence of resin composites with the background color was evaluated. The objective was to
measure since what thickness the color of the sample stops being influenced by the color of the background over which
the resin is placed and the methodology used in experiment was based in analyzing the contrast of digital images of the
sample over a black background. The results shown that since 0.8 mm the images contrast becomes almost constant; it
prove that since this thickness the color of resin composite depends on the optical resin properties only. The experiment
was repeated under three conditions of luminosity to evaluate the influence of it on the image contrast and the results
obtained were identical.
Selection of the proper shade and color matching of restorations to natural dentition continues to be one of the most frustrating problems in dentistry and currently available shade guide presents a limited selection of colors compared to those found in natural dentition.
This investigation evaluation if the composites resins shade B2 are equivalent to the Vita shade guide B2.
Twelve composite resins (Renamel Microfill Super Brite- Cosmedent USA, Renamel Universal Brite- Cosmedent USA, Renamel Microfill Body- Cosmedent USA, Renamel Universal Body- Cosmedent USA, Opallis EB2-FGM, Opallis DB2-FGM, Filtek Supreme XT-3M/ESPE, Filtek Z250-3M/ESPE, Filtek Z350-3M/ESPE, Z100-3M/ESPE, 4 Seasons Dentin-Ivoclar/Vivadent, Tetric Ceram-Ivoclar/Vivadent) shade B2 were used. From each composite, two specimens were made in a steel matrix with 8.0 mm diameter and 10.0 mm different predetermined thickness (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 mm). The specimens were 40 seconds light polymerized by LED Ultrablue (DMC). The specimens were measured 10 times each to determine the shade using a reflectance spectrophotometer (Pocket Spec).
According to results was verified that not any of composites resins shade B2 evaluated in this study presented values of color difference (ΔE) equivalent to the Vita shade guide B2 and the 2 mm thickness showed the closer match to the Vita shade guide B2.
The dental bleaching is known for many years. Recently a technique employing light has
open up new and exciting possibilities. Besides its vast application there are still many
important points to be understood about teeth photon bleaching. In this work we present an
"in vitro" experiment to explore the main mechanisms involved during the photon action in
tooth whitening. Our results indicated that light at same wavelengths are great absorbed by
pigments creating a local heating which considerably increase the bleaching rate. This
results in a fast reaction without heating the whole dental structure. We discuss details of
our experiment. Work supported by Fapesp and CNPq.
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