An in vitro comparison of bleaching methods for discoloured non-vital teeth

Objectives: The aim of this study was to compare three different methods of bleaching non-vital discoloured teeth. Methods: 40 extracted premolar teeth with intact crowns were stained intrinsically with blood products. The teeth were randomly and equally divided into four groups: a control and three bleaching groups. Method 1: 10% carbamide peroxide gel loaded into a custom fitted bleaching tray for 8 hours each day; Method 2: Sodium perborate mixed with sterile water, sealed into the access cavity and changed weekly; Method 3: 10% carbamide peroxide gel sealed into the access cavity and changed weekly; Method 4 (control): Sterile water in the access cavity changed weekly. The colour of the mid-labial tooth surface was recorded using a colorimeter before bleaching, and at intervals of 1 day, 7 days and 14 days. Colour was computed on the CIE L*a*b* colour space system. Results: The mean value for lightness (L) increased for all four methods. Significant differences (p<0.005) between lightness at day 0 (L0) and at day 14 (L14) were seen for methods 1, 2 and 4. The greatest mean difference was for method 2 (p<0.001). Conclusions: A number of methods were effective in bleaching teeth in which blood products were the cause of discolouration, however the greatest change in lightness was achieved using sodium perborate and water.