On the permanence of tooth bleaching

Bleaching (alias whitening) is increasingly the chosen means of modifying the appearance of teeth for cosmetic reasons. Behbehani et al. (2012) acquired the largest known data set for the effects of bleaching over time (300 patients for ∼1year), but the analysis then was rather superficial and did not exploit the full depth of information available in it.

Data collected by Behbehani et al. (2012) were re-analysed to explore in detail the variation in outcome between patients and over time.

There is a distinct regression in shade scale value with time, taking something over 1year to approach stability. There appears to be an intrinsic shade that cannot be altered, at around 1 unit (0.5M1 on the Vita 3D bleached shade guide). Some patients (11/300 at 1year) appear to be worse-off after treatment, especially those with lighter starting shades, while many get no real benefit, with a change ≤2 units.

The effects of bleaching are often transient, but the reversion to a darker shade than the original may be due to the cumulative damage done to the organic matrix of enamel. The ethics of the treatment are questioned, as are over-the-counter products and whitening toothpastes. It might be appropriate to suggest to a patient that there is no point unless the shade is darker than some (Vita) shade value, say ∼1M2, but in any case informed consent is in need of improvement. All observations of the effects of bleaching ought to be made on timescales longer than 1year to be meaningful.