Disadvantages of paint-on teeth whiteners (Colgate Simply White Night ® and Crest Night Effects ®).

One general criticism of paint-on teeth whitening products is associated with their ability (or lack thereof) to stay put on a tooth's surface long enough to create whitening results. Teeth whitening with peroxides is simply a case of cause and effect. To achieve tooth lightening an appropriate peroxide whitener must be in contact with the tooth's surface for an appropriate duration of time. If these conditions are not met, the whitening effect produced will either be very minimal or take an extended number of treatments.

Other types of teeth whitening systems use delivery appliances that aid in creating contact between the bleaching agent and the surface of the teeth being lightened. "Tray-based teeth whitening" refers to a technique where a bleaching gel is placed into a plastic tray that is then placed over the user's teeth. The tray insures intimate contact between the bleaching gel and each tooth's surface. The tray also protects the gel somewhat from being diluted or washed away by oral fluids.

Teeth whitening strips offer yet another means by which to deliver a bleaching agent to the surface of teeth. With this technique a plastic strip that has been impregnated on one side with a bleaching agent is placed on the surface of the teeth being treated. While it doesn't seem likely that a strip can provide the same degree of intimate contact with tooth surfaces as a bleaching tray can, or protect the bleaching agent from the oral environment as well, the studies we have reviewed seem to suggest that the use of whitening strips can approach the effectiveness of tray-based systems.

As opposed to tray-based or whitening strip methodology, the nature of paint-on teeth whitening technique does not afford the same degree of protection for the whitening agent. While clearly the whitening film does achieve direct contact with the tooth surface, the person's oral environment will have a significant effect on how well the whitener is able to stay intact and in place.

The instructions for paint-on products typically suggest that the surface of the teeth should be dried first. Either 30 seconds of air drying or else wiping the teeth with a washcloth. It seems that this step helps to improve the adherence of the film to teeth. The instructions also usually encourage the user to minimize activities that might dislodge the whitening film. The avoidance of rinsing, eating, and drinking and also minimizing the amount of friction produced by lip, cheek, and tongue movements aids in preserving the integrity of the whitening film.

We did find one study that specifically addressed the issue of retention of paint-on teeth whitener during teeth bleaching treatments. Our Date, 2003 reference added a dye to Crest Night Effects ® so they could evaluate how much of this product was dislodged during use. This study determined that 3/4ths of the bleaching film remained in place during overnight bleaching treatments.

How easy is it to apply a paint-on teeth whitener?

Another criticism aimed at paint-on teeth whitening products has to do with their ease of use. The application of paint-on teeth whiteners, while seemingly easy, can be awkward. Drying teeth, applying the product, ensuring application of the whitener to the entire surface of each tooth can each be more of a challenge than one might expect.

Our Date, 2003 reference evaluated user application of paint-on whitener. They added a blue dye to Crest Night Effects ® samples so they could determine the extent to which coverage of the front side of front teeth of each user was achieved. They determined that the study's participants were able to accomplish 85% coverage. Clearly a tray-based teeth whitening system would achieve a greater degree of coverage.

How effective are paint-on teeth whiteners as compared to other at-home teeth whitening products?

We were unable to find any reference to any dental study that directly compared the relative effectiveness of the four primary types of at-home teeth whitening systems (tray-based teeth whitening using a carbamide peroxide bleaching gel, whitening strips, paint-on teeth whiteners, and teeth whitening toothpaste). In fact, most of the literature we found regarding paint-on teeth whiteners only compared their use to no treatment, other paint-on products, or else teeth whitening toothpastes. This seemed to suggest to us that many studies were purposely designed so a direct comparison between paint-on teeth whitening technique and other at-home bleaching systems known to be effective was avoided.

Our review of dental literature has allowed us to formulate an opinion about the relative effectiveness of paint-on teeth whitening products. Our opinion is that a person will most likely achieve a greater degree of tooth whitening, and achieve it more quickly, when using either a tray-based teeth whitening technique with a carbamide peroxide bleaching gel or else teeth whitening strips (assuming all other factors are equal).

This is not to suggest that paint-on teeth whiteners do not work. Peroxide-based teeth whiteners absolutely can produce results. But in regards to being able to deliver an effective bleaching agent to a tooth surface for an adequate amount of time, tray teeth whitening with a carbamide peroxide gel or else teeth whitening strips seem to have the upper hand.

Are all paint-on teeth whiteners equally effective?

It would be our opinion that the forms of paint-on teeth whiteners that are intended for overnight use (Colgate Simply White Night ®, Crest Night Effects ®) produce better whitening results than their daytime counterparts (Barlow, 2003). However, we do not know if this is related to:

• The longer treatment time typically associated with the use of an overnight paint-on whitener.
  
  
• The ability of an overnight paint-on product to create a more adherent film on the tooth's surface (our conjecture).

or a combination of both.