Teeth Whitening: What Actually Works

How whitening works

Peroxide-based gels break down the pigment molecules trapped within the enamel and the underlying dentine layer of the tooth. In-office systems use higher concentrations of peroxide under controlled gum protection and sometimes a curing light, producing visible results within a single appointment.

Custom-made home trays use a lower concentration of gel worn over one to two weeks, giving a gentler but equally effective route to a lighter shade for most people. Many practices combine an initial in-office session with take-home trays to maintain and extend the result.

What whitening will not change

Crowns, veneers and composite fillings do not respond to whitening gel and will not lighten alongside the natural teeth. If these restorations are visible in the smile, whitening the surrounding natural teeth first and then matching new restorations to the lighter shade is the usual approach.

Deep tetracycline staining from childhood antibiotic exposure, fluorosis marks, and a single dark root-treated tooth all respond poorly to conventional whitening and are better managed with veneers, bonding or internal bleaching of the specific tooth.

Sensitivity and safety

Temporary sensitivity to cold is common during and shortly after a whitening course and usually settles within twenty-four to forty-eight hours of finishing treatment. Desensitising gels applied before or after whitening, and spacing out sessions, manage this well for almost everyone.

Whitening should always follow a professional cleaning and a check for untreated decay or exposed root surfaces, since applying peroxide gel over an unhealthy tooth or exposed dentine can cause significant discomfort.

Maintaining the result

Whitened teeth are not immune to future staining from tea, coffee, red wine, tobacco or turmeric-rich foods. A touch-up with home trays every six to twelve months, along with routine cleaning visits, keeps the result looking fresh for years.