Clinical study of the safety and effectiveness of a novel over-the-counter bleaching tray system.

Although paired comparisons of color change after 50-minutes versus after 3 months in the 28 subjects with measurements at both time points revealed a borderline significant difference ( P =0.048; t -test for paired comparisons), it is interesting to note that six subjects actually experienced 0.5 to two shades improvement in color change during follow-up.

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