TiO2 nanoparticles whiten without peroxide, but the fresh suspension lagged behind

A photocatalytic suspension whitened teeth without peroxide

At-home whitening rests almost without exception on peroxides. The team publishing in the Brazilian Dental Journal tested an alternative: a suspension of titanium dioxide nanoparticles that is activated by ultraviolet light and contains no peroxide. They were also interested in something rarely examined — whether the same suspension can be used more than once.

Forty bovine incisors underwent a 21-day at-home protocol, two hours a day, in four groups of ten samples: fresh 16% carbamide peroxide, the same peroxide collected and reapplied, a fresh 10% TiO2 suspension and a reactivated TiO2 suspension. The suspensions were activated daily with UV light at a wavelength of 385 nm for 50 minutes, and the reused one was reactivated before each application. The pH of all preparations moved the same way, from 6.0 to 7.0 over the protocol. Colour change was measured with a VITA Easyshade V digital spectrophotometer, through CIEDE2000 and the whiteness index.

The finding runs against expectation. The smallest colour change came from the fresh TiO2 suspension, with values closest to the perceptibility and acceptability thresholds, and it differed significantly from the reactivated suspension and from both peroxide groups (p < 0.05). All the other groups crossed the acceptability threshold, and among them there was no difference. The whiteness index did not differ in any comparison (p = 0.475).

Limitations

The work is in vitro, on bovine incisors and with ten samples per group. The abstract does not explain why the reactivated suspension outperformed the fresh one, nor does it report data on enamel roughness or tooth sensitivity.

For your practice

• Change nothing in your protocol for now: the experiment was run on bovine teeth with daily laboratory UV activation, not in a patient's mouth.
• Tell patients asking for peroxide-free whitening exactly this: titanium dioxide photocatalysis exists in the laboratory, clinical evidence does not yet.
• The observation that pH moved between 6.0 and 7.0 is a useful argument in any conversation about the acidity of at-home whitening preparations.