2008 Volume 51 Issue 2 Pages 203-209
When investigating of vital tooth bleaching, it is considered difficult to simply apply a clinical result as an index for evaluating the bleaching effect, because of individual variations as well as varied staining substances and degrees of staining. Even in the case of in vitro bleaching experiments, it is also difficult to obtain evenly stained enamel with no individual variation in a relatively short term due to the structural properties of enamel. Thus, an alternative sample that can serve as a standard for evaluating the effects of bleaching is desired. Based on the assumption that a brown eggshell could serve as an effective sample for evaluating vital tooth breaching, we had previously examined the eggshell structure and the stability of staining in relation to the bleaching effect using a colorimetry the result of which suggested its possibility. In the present study, therefore, the bleaching effect in relation to light irradiation time was examined using two commercially available office bleaching agents in Japan, in order to elucidate the possible utility of brown eggshell as an evaluation sample with the aid of a halogen lamp light irradiator for composite resin polymerization. With regard to the bleaching effect, L*, a*, b* value at each irradiation time was calculated by colorimetry, and the effect was then evaluated based on ΔL*, Δa* and Δb* as well as the difference in coloration before and after bleaching to examine a possible approach for evaluating the bleaching effect achieved using brown eggshells. As a result, the following conclusions were obtained: 1. With the aid of light polymerization irradiator used in this study, it was revealed that light irradiation lasting about 4 minutes is most suitable for bleaching in the case of Shofu Hi-Lite 2. With the aid of light polymerization irradiator used in this study, it was indicated that the bleaching could be done more effectively with a prolonged irradiation time in the case of Pyrenees. In the present experiment condition, the most effective time result could be obtained in maximum 9 minutes. 3. In the breaching of the brown eggshell, it was considered that the bleaching effect could be evaluated using ΔL* values before and after bleaching.
