Effectiveness and color stability of bleaching techniques on blood-stained teeth: An in vitro study

Abstract

Objective: Evaluate the effectiveness and color stability of bleaching techniques on blood-stained teeth.

Material and methods: The teeth were stained by blood and allocated to groups: walking bleach, inside/outside, and in-office bleaching. L*, a*, b*, C*, h° color coordinates were measured using a clinical spectrophotometer at baseline, weekly (T1-T2-T3), and at 1-week (T4), 6-months (T5), and 1-year (T6) follow-up evaluations. ${\mathrm{\Delta E}}_{\mathrm{ab}}^{*}$ , ${\mathrm{\Delta E}}_{00}$ , and ${\mathrm{\Delta WI}}_D$ were calculated between sequential evaluation timepoints and between baseline and each evaluation timepoint. Color coordinates and WI_D differences in each timepoint and technique were analyzed by Wilcoxon Signed Rank, Kruskal-Wallis and Mann-Whitney U test, respectively. ${\mathrm{\Delta E}}_{\mathrm{ab}}^{*}$ , ${\mathrm{\Delta E}}_{00}$ , and ${\mathrm{\Delta WI}}_D$ were interpreted by color visual thresholds.

Results: The techniques presented a significant increase in L* and WI_D and, a significant decrease in a* and b* until the completion of treatments. Statistical differences between the techniques for a*, b* and WI_D were observed from T1 until T3. All techniques demonstrated excellent effectiveness for ${\mathrm{\Delta E}}_{\mathrm{ab}}^{*}$ , ${\mathrm{\Delta E}}_{00}$ , and ${\mathrm{\Delta WI}}_D$ between baseline and each evaluation and follow-up timepoints. However, at T6, it was possible to identify a rebound effect for all techniques.

Conclusions: All bleaching techniques presented excellent effectiveness. The stability of the whitening produced was maintained for 6 months.

Clinical significance: Effective whitening of blood-stained teeth was achieved using walking bleach (sodium perborate), inside/outside (hydrogen peroxide - 7.5%) and in-office techniques (hydrogen peroxide - 35%). The bleaching techniques were effective after the completion of the treatments. A slight rebound was observed at 1 year follow-up.

Keywords: blood stain; color difference; color visual thresholds; hydrogen peroxide; nonvital tooth bleaching; sodium perborate.