Objectives: To evaluate the effectiveness of Opalescence PF 10% just after treatment, at 6-month follow-up and at a 14-month follow-up period. Methods: Opalescence PF 10% was applied nightly for 14 days. The color of teeth 11 and 21 of 17 subjects were measured with a spectrophotometer (L*; a*; b*) before treatment, just after treatment (14 days), after 6 months and after 14 months. Subjects were instructed to take note of any tooth sensitivity.Results: For all three components (L*, a* and b*) statistical significant differences ( p < 0.05) in the values between base-line, after treatment (14 days later), after 6 months and after 14 months were found (Wilcoxon Signed Rank Sum Test). The decrease in L* was about 20% after 6 months and about 50% after 14 months. The a* value decreased approximately 14% after 6 months but was worse after 14 months than at the beginning. The b* value decreased the least with about 9% after 6 months and about 8% after 14 months. The decrease in DE_ ab was _20% after 14 months. Less than 20% of the subjects experienced mild tooth sensitivity just after treatment.Conclusion: Significantly whiter teeth were found after treatment as well as after a 6-month follow-up period. The whiteness/brightness (L*) decreased with _50% after 14 months and the a* value with _50% after 7 months, while the yellowness (b* value) remained even after 14 months.Clinical implications: The product is an effective tooth whitener resulting in only low tooth sensitivity. Re-bleaching could be done at about 14 months.

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