Teeth whitening

Color is not just on the surface

The enamel allows part of the light to pass towards the dentin, which is naturally yellower. The visible color therefore depends on several fabrics, their thickness and their optical properties. Removing a coffee deposit can improve the exterior appearance without changing the underlying color. Conversely, a clean tooth may retain a completely normal ivory shade.

Peroxide transforms colored molecules

Peroxides diffuse into dental tissues and react with molecules responsible for coloring, called chromophores. These oxidation reactions modify their structure and their absorption of light. Lightening therefore does not consist of sanding off a yellow layer: it acts chemically on the color, which distinguishes it from cleaning superficial stains.

Carbamide peroxide releases hydrogen peroxide. The percentages indicated on the two types of gels are therefore not directly comparable: 10% carbamide corresponds approximately to 3.5% released hydrogen peroxide. This equivalence explains the labels; it is not used to make a mixture or to choose an exposure time yourself.

A real effect, but not an identical result for everyone

The 2018 Cochrane review brings together 71 trials involving 3,780 adults. She notes short-term clearing compared to placebo, but rates the evidence as low to very low certainty. Differences in products, concentrations and protocols make it impossible to conclude that a home method would systematically be the best.

The starting shade and the origin of the coloring also matter. Discoloration linked to certain medications may require different treatment than common yellowing. The materials of crowns, veneers or composites do not react like dental tissues: the treatment can therefore lighten the teeth while leaving a visible restoration of its original color.

A lamp does not guarantee more whiteness

LEDs and lasers make the treatment very visible, but their benefit must be evaluated separately from that of the gel. A meta-analysis published in 2019, including 28 studies, does not find superiority of light activation for color change in the office. This does not mean that the gel is ineffective: it calls into question the benefit added by light.

Sensitivity is one of the limitations of treatment

Products may cause tooth sensitivity and irritation when touching soft tissues. In home bleaching trials, these effects were generally temporary, with more problems at higher concentrations. Increasing the dose or duration therefore does not constitute an automatic improvement in treatment; comfort and tooth response should guide follow-up.

Whitening toothpastes have another role

A whitening toothpaste can help remove surface stains, but it does not necessarily produce the same color change as a whitening gel. Brushing harder does not improve this action and can damage the tissues. Charcoal and homemade acidic preparations do not offer a proven safer alternative: above all, choose a fluoridated toothpaste and a method suitable for coloring.