Effect of whitening with 10% carbamide peroxide still visible after five years

The lightening survives five years, but part of the colour returns in the first four months

At-home whitening with 10% carbamide peroxide in a custom tray is one of the oldest protocols in esthetic dentistry, yet the question every patient asks — how long will it last — has rarely been answered with data extending beyond a year or two. The team around Hampé-Kautz therefore followed the same cohort for a full five years.

The protocol was standard: four weeks of nightly tray wear with 10% carbamide peroxide in 49 patients. Colour was recorded by standardised photography at baseline and at the end of treatment, then after four months, after two years and, in the 19 patients who remained in follow-up, after five years. The whiteness index and the colour difference according to the CIEDE2000 formula were calculated from the L*, a* and b* coordinates, with lightness, chroma and hue tracked separately.

The effect curve proved steep at the start and flat afterwards. The largest shift in colour and in the whiteness index occurred within the first week of wear, and in the following weeks and months the gain progressively diminished. The colour rebound recorded four months after stabilisation was clearly noticeable compared with the colour before stabilisation. The individual colour components did not behave alike: lightness changed markedly during treatment but also relapsed fastest; chroma changed considerably in both arches and proved the most stable; hue changed the least. After five years the effect was still clinically visible, with a gradual and expected colour rebound.

Limitations

The study has no comparison group without whitening, and the dropout is large — from 49 patients at baseline to 19 after five years, which makes the five-year finding the weakest link in the chain.

For your practice

• Explain the shape of the curve to the patient in advance: the largest jump in whiteness comes in the first week, so expectations for the third and fourth week should be realistic.
• Schedule a colour check around the fourth month — that is when the rebound is most noticeable and when it makes sense to discuss refreshing the gel.
• Standardised digital photography proved reliable for long-term follow-up; a simple in-office photographic protocol is worth more than memory and a shade guide.