Is Tooth Whitening Effective?
The first aspect of tooth whitening (sometimes called tooth "bleaching") to recognize is that to be truly effective, and clinically significant, the whitening agent (usually a form of hydrogen peroxide or carbamide peroxide) effectiveness depends on two major factors:
- Strength (concentration) of the whitening agent
- Length of contact of the gel with the tooth surface
For these reasons, most over-the-counter "whitening rinses" or "whitening toothpastes" produce minimal esthetic results. The peroxides included in them are very diluted and in contact with the teeth for usually less than 2 minutes. They cannot effectively whiten teeth at those low concentrations and for such short periods of working time.
Alternatively, over-the-counter whitening strips, coated with higher concentrations of peroxide gels, remain in contact with the teeth from 30-60 minutes, making them much more effective. Many patients find these effective enough to satisfy their cosmetic dental goals.
The effectiveness of tooth whitening also depends upon the specific individual's age and initial tooth shade. Older teeth are naturally darker and more resistant to whitening, and certain shades of teeth (gray or brown shades) are much harder to whiten than other shades (such as yellow). It should also be remembered that restored teeth (with porcelain crowns, veneers, or composite fillings) cannot be whitened, and their shades will not match the whitened teeth and my need to be replaced to establish a cosmetic result.
Is Tooth Whitening Damaging To Teeth?
Decades ago, bleaching gels were acidic and could damage enamel and root surfaces. However, current whitening gels are buffered to have a neutral pH and do not etch teeth. The gels themselves do not damage the enamel, but the peroxides in the gels can burn the gingival tissues (gums) at the base of the teeth. Certain products used in the dental office are used in conjunction with heating or laser light applications and can cause unpredictable tooth sensitivity due to irritation of the pulp (nerve) of the tooth. Root surfaces are very porous when viewed under a microscope exhibit thousands of tiny (tubule openings (pores) that can react unpredictably to the application of heated or light activated peroxides. This can result in severe tooth sensitivity or even the need for root canal therapy. The whitening effects of heated or laser-activated gels is usually due to the immediate dehydration of the tooth and rebounds back to a darker shade when the tooth rehydrates.
The technique which best balances effectiveness with gentleness to the pulp is tray whitening, where carbamide peroxide gels (which are less irritating than hydrogen peroxide gels) of varying strengths are placed in custom trays and held against the teeth for between 30 minutes and overnight. Tray whitening does not usually promote severe tooth sensitivity and if any sensitivity is encountered the whitening can be suspended immediately.
For detailed and specific information regarding bleaching reference our Tooth Whitening course .