Examination of Bleaching Techniques of Vital Tooth : Evaluation Study on Bleaching Effect by Means of Brown Egg Shell and Surface Roughness by Human Enamel

Abstract

Bleaching methods for vital tooth currently performed in dental clinics can be roughly divided into three approaches including office, combination and home bleaching manipulations. The present study was performed in order to compare not only the bleaching effectiveness of different conventional techniques generally employed in dental practices on brown eggshell, but also to examine the influence of these techniques on the human dental enamel surface. Concerning the bleaching effectiveness, ΔL* was calculated from L* values obtained before and at arbitrary times after bleaching by means of a colorimeter that read the contact-type tristimulus directly for comparison. Furthermore, ΔE*ab was also calculated from L*a*b* values similarly obtained in order to examine a possible correlation between ΔE*ab and ΔL* and to propose a simplified method of expressing the bleaching effectiveness. As for the influence on the enamel surface, the surface roughness before and after bleaching was measured by a scanning probe microscope, using a human extracted tooth-derived enamel, and the influence of individual bleaching techniques on the enamel surface was then examined based on the ΔRa thus calculated. As a result, the following conclusions were drawn: 1. The macroscopic bleaching effect was found to be greater in the following order of office, combination and home bleaching. 2. Concerning ΔL* obtained from different bleaching techniques, the value was approx. 17.7 after one treatment and approx. 24.9 after 3 treatments in the case of office bleaching. In the case of combination the bleaching, ΔL* value was approx. 17.6 after one treatment, increased with repeated application of home bleaching, and finally reached approx. 19.4 after 14 treatments. As for the home bleaching, ΔL* increased gradually with repeated application but still remained around 6.5 even after 14 treatments. 3. A distinct correlation between ΔL* and ΔE*ab was confirmed at γ=0.90 or more for all bleaching techniques examined. 4. When the surface roughness expressed as ΔRa was examined by using a human extracted tooth-derived enamel, the value for office bleaching manipulation was significantly larger than those for combination and home bleaching manipulations. No significant difference was, however, observed between combination and home bleaching manipulations.