Digital evaluation of dental bleaching. A 5-year in vivo study

The objective of the present study was to assess tooth color changes over a 5-year period after at-home bleaching protocols with 10% carbamide peroxide.

A 4-week overnight at-home bleaching protocol using whitening trays and 10% carbamide peroxide was performed on a total of 49 patients. Tooth color was analyzed in 49 patients using standardized photographs at the beginning of treatment, the end of treatment, after 4 months, after 2 years, and again after 5 years for the 19 still-remaining patients. The values for the color coordinates L*, a*, and b* were recorded and used to calculate the whiteness index (WID) as well as the color difference (ΔE 00), luminosity (L*), chroma (C*), and hue (h°) variation using the CIEDE2000 formula. Statistical analysis was conducted at a significance level of P 0.05, by means of paired Student's t tests.

The color difference and the whiteness index difference were greatest during the first week of treatment and decreased progressively in the subsequent weeks and months. The relapse in color observed 4 months after stabilization showed a noticeable difference compared with the color prior to stabilization. Luminosity showed a significant difference between the beginning and the end of treatment as well as a marked relapse. Similarly, chroma underwent substantial variation during treatment in the teeth of both arches, yet showed only minimal relapse. In contrast, hue displayed only minor changes throughout the treatment and stabilization periods.

The present study confirms the long-term efficacy of at-home bleaching with 10% carbamide peroxide. The whitening effect remained clinically noticeable after 5 years, despite a gradual and expected relapse. Among the color parameters, chroma was the most stable, while luminosity showed an early relapse, and hue showed a minimal relapse. Standardized digital photography proved reliable for long-term color monitoring.