Bleaching of Vital Tooth : Application of Brown Eggshell as a Bleaching Standard

Abstract

For the assessment of bleaching effect on vital teeth, various approaches have been performed in the clinical practice including subjective assessments before and after operation or objective ones using a measuring tool, and a number of reports have examined its clinical efficacies. However, it seems difficult to apply the clinical efficacy thus obtained solely as an index for evaluating the bleaching effect because of potential individual variations and/or differences in the degree of coloring. Even in the in vitro experimental model for bleaching, it was difficult to have evenly colored enamel with no individual variation within a relatively short time due to the structural property of enamel. Therefore, an alternative sample which can be used as a standard for evaluating the bleaching effect is desired. We have searched for a material capable of assessing the bleaching effect on vital teeth simply and distinctly. The present study examined whether or not brown eggshell is suitable as an index for evaluating the bleaching effect through examinations on the structure of brown eggshell, its altered colors in response to the use of ethanol or acetone, potential individual differences in the color of an eggshell, and altered colors in response to the state of eggshell or those with times. Altered colors before and after application were assessed on a color measuring scale by using an office bleaching agent. In consequence, it was confirmed that an eggshell usually has both good and poor light-permeable portions with individual variations irrespective of the kind of egg used. It was also suggested that the color shows no change in response to the use of ethanol or acetone and the color of an individual egg which was selected after light-permeable check was relatively homogeneous except for both apical sites. In addition, it was found that the determined color score differs according to the state of the eggshell, that is, moistened or dried state, and the color of the eggshell changes with time elapsed. However, a relatively stable result could be obtained by preserving the shell in a thermostatic chamber for one day after boiling. In an actual experiment using an office bleaching agent, a distinct difference was observed macroscopically and the L*a*b* values showed characteristic changes. In summary, it is suggested that a brown eggshell can be applied as a bleaching standard for evaluating the effect of vital tooth bleaching agent.