The bleaching agent that is applied to whitening strips (Crest Whitestrips ®) is hydrogen peroxide. The first whitening strips product that was brought to market (Whitestrips ® Classic) contained strips that were coated with a 6% hydrogen peroxide whitener. As a variation, whitening strips can also be purchased that have a 9.5% (Whitestrips ® Renewal) or 10% hydrogen peroxide coating (Whitestrips ® Premium and Premium Plus).
The general consensus of dental research and the the dental community as a whole is that the whitening effect produced by peroxide whiteners is simply a function of concentration and time. In the case of whitening strips this is evidenced by the instructions that come with these products. The 10% hydrogen peroxide whitener strips are intended for use over a course of 7 days whereas the 6% kits come with enough strips for 14 days of treatments (twice as long as the more concentrated strip).
The composition of the bleaching agent is itself adhesive and therefore helps to hold the strip in intimate contact with the surface of the teeth being bleached. And since only one side of the whitening strip is coated with the whitener, the plastic strip itself serves as a barrier that minimizes the contact of the bleaching agent with saliva and users soft tissues. This both increases the effectiveness of the whitening process and reduces the whitener's potential for creating side effects.
The nature of the chemistry associated with hydrogen peroxide teeth whitener is essentially the same as when carbamide peroxide (the whitener that is characteristically employed with tray-based teeth whitening systems) is used. In fact, in the oral environment carbamide peroxide whiteners break down into hydrogen peroxide and urea. The hydrogen peroxide component being the one that produces the teeth bleaching effect.
In general, peroxide-based teeth whitening is thought to involve thin-film chemistry. This simply means that to achieve a bleaching effect one does not need to use a lot of peroxide but just enough to cover over the surface of the teeth that need to be lightened. The idea of teeth whitening strips as a product simply takes the concept of thin-film chemistry to an extreme. In the case of whitening strips the whitener that is applied is roughly .20 millimeters thick. A piece of paper generally measures about .1 millimeters in thickness.
There is no way to know for certain what type of whitening results a person will be able to achieve with any type of teeth whitening products. The results people experience when whitening their teeth are variable, period. This is because the teeth of any given population will display a number of different types of tooth staining that have been produced by a variety of causes. As a result, each person will have their own unique level of bleaching potential.
An evaluation of the overall effectiveness of teeth whitening products can be somewhat difficult to determine. In any given study there will be variability related to specifically which participants (by chance) were assigned to which group. There will also be variables such as which whitening systems are compatible with the user's lifestyle and perceptions of whitener use. Since peroxide-based teeth whitening is simply one of cause and effect (meaning the use of an appropriate whitener for an appropriate period of time) the compliance of the user with the whitening system's instructions is of paramount importance in obtaining results.
The published clinical studies we have reviewed seem to suggest that teeth whitening strips coated with 6% hydrogen peroxide whitener can be expected to provide similar whitening results as tray-based systems employing a 10% carbamide peroxide whitener (a technique which at this point is generally accepted to be the unofficial standard for at-home teeth whitening systems). As alluded to previously, since teeth whitening is simply a case of cause and effect, when choosing between teeth whitening strips and a tray-based system, selecting the system whose instructions you find easiest to comply with it typically the best choice. Compliance to the instructions of a whitening technique is easily as important as specifically which methodology is chosen.
The stability of the bleaching results a person achieves when using teeth whitening strips can be expected to be similar in nature to those results achieved when using any peroxide-based teeth whitening products. This is because the fundamental science of the bleaching process is the same with all peroxide whitening systems. Some studies that have evaluated the longevity of the results achieved when using strip-based bleaching have found no significant color relapse after 6 months. These findings seem on par with those results that have been reported for tray-based teeth whitening systems.
Of course each person will have their own individual experience as far as the degree of whitening relapse they experience and their need for touch-up bleaching treatment. Those people who regularly expose themselves to chromogenic agents and events such as coffee, tea, colas, red wine, and smoking will likely find that their tooth color relapses more rapidly than for those who don't. These people will simply need to perform touch-up whitening treatment more frequently.
Since the total amount of color change that is needed during touch-up whitening treatment is typically less than that amount of change produced during the original bleaching process, one can anticipate that the number of whitening treatments needed to achieve their touch-up whitening goals will be fewer.
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