In vitro color stability of provisional restorations.

A provisional restoration must protect the prepared tooth, provide comfort and function and be esthetically acceptable and color stable. This study measured the degree of color change of provisional restorations. Five commercially available resins were evaluated: Trim, Tab, Kind, Snap and Duralay. Five cylindrical samples of each resin were fabricated by mixing the powder and the liquid to a predetermined ratio and pouring the mix into a mold. The Minolta Chroma Meter II Reflectance was used to establish the baseline color L* a* b*. The resins were then subjected to accelerated in vitro aging in a Weather-O-Meter and color readings were recorded. The color differentials on delta E* were computed for each sample (delta E*ab = [(delta L*)2+(delta b*)2]1/2). The difference is a quantitative measurement of color change. The National Bureau of Standards describes delta E* as units (NBS Unit = delta E*ab x 0.92). With this parameter only the allowable delta E*ab need be specified rather than the range of allowable L*, a*, b* values. This is important for color comparison and quality control functions. The results showed that Kind had a slight color change delta E* = -1.72, Trim demonstrated the most color change delta E* = -13.84, while the remaining resins demonstrated a noticeable change in color due to in vitro aging.