Tooth whitening: tooth color changes following treatment by peroxide and light

This study examined the use of color measurement to determine tooth color in a study of bleaching with peroxide and light used separately and in combination. Two measurement protocols were evaluated for their ability to reveal differences between treatments and confirm tooth shade evaluations.

Before and after treatment, 43 subjects were evaluated for tooth color using a shade guide and a chromameter. Two measurement procedures were used: one measured a single location on each tooth using a fabricated plastic stent, and the other measured nine locations across the buccal surface. Values from the two procedures were compared to each other, and to shade guide measurements.

Tooth color, as measured by both procedures, significantly correlated with shade evaluation. Statistically significant differences between treatment groups were found more often with data from the multiple-site procedure than from the single-site procedure. Incisal-gingival color gradation on tooth surfaces was diminished as a result of whitening treatments. Chromameter measurement data showed that tooth whitening procedures reduced tooth yellowness (b) more reproducibly than they increased whiteness (L).

When more sites per surface were measured, tooth color measurement by the chromameter more closely matched shade with less variability and greater statistical power. Chromameter-derived values can be used to estimate shade values to a reasonable level of accuracy. Decreasing yellowness, particularly at the gingival margin, was an important component of the tooth whitening effect. Following tooth whitening, teeth were more uniform in their color, and this may contribute substantially to the subjective patient recognition of whiter teeth.