2008 Volume 51 Issue 4 Pages 411-418
In response to the demand for opaque resin for esthetic restorations in recent years, various kinds of opaque resin have become available. However, because an opaque resin itself has many kinds of color and various colorations tend to be produced due to some combination with the subsequently layered composite resin, it is difficult to decide the optimal combination for restoration instantly in the clinical practice. Since such difficulty may be avoided by developing an opaque resin with reduced coloration, we have investigated such vesins by using TP values as an index of background color shielding and permeability. In this experiment, the color of dentin in an abutment tooth which was prepared for full veneer crown of vital tooth was first determined and the shade was examined in order to obtain the standard color of opaque resin. An opaque resin of the standard color was prepared by adding three kinds of paint to a composite resin of which the filling rate of zirconia filler was changed. Onto these opaque resins, composite resin samples of Shade A1, A2, A3, A3.5, A4, B1, B2, B3, B4, C2 and C3 were placed and their TP values were determined by using a colorimeter of the contact-type tristimulus value direct reading style in order to obtain a unique opaque resin with minimum content of zirconia filler and the background color was shielded successfully. As a result, the following conclusions were drawn: 1. As for the dentin color of vital tooth, 4 out of 7 teeth examined showed A 3.5 in Vita shade. 2. The background color shielding effect of the opaque resin sample was increased in response to the increased filling rate of zirconia filler. 3. As for the background color shielding effect of layered samples, TP value of 2.0 or below was confirmed for all layered composite resins, provided that the opaque resin sample had A3.5 shade and 6% filling rate of zirconia filler. 4. Concerning the prediction of TP values for layered samples, it was suggested that TP values determined at different times during the course of layering could be predicted from TP values of opaque resin and composite resin samples.
