Posted on July 5, 2018
While the color of one’s teeth may appear to be the only concern when it comes to tooth whitening kits, the color of the solution itself can actually play a significant role, as it plays a major part in that consumer’s perception of quality and efficacy; while the results of a tooth whitening solution matter, the color of the solution matters just as much and manufacturers generally aim for a clear end product that suggests a vivid, clean result. Although these associations are in part psychological, color can also be a very real sign of efficacy, making strict color quality control critical.
Unfortunately, when working with multiple chemicals, color accuracy and consistency can be difficult to maintain. Slight reactions between the components of your solution could cause the color to turn an unappealing shade, become cloudy, or cause the active ingredient to break down, reducing the impact of the blend. Because the color of oral care products such as whitening solutions has both significant aesthetic and functional implications, it is important that operators are able to locate and resolve color problems rapidly. This can be achieved by integrating spectrophotometric color measurement as a central component of your color quality control protocols.
Why Color Matters in Tooth Whitening Solutions
Typically, the active ingredient in whitening solution is either hydrogen peroxide or carbamide peroxide, which are naturally clear or white in color. However, both hydrogen peroxide and carbamide peroxide are susceptible to color changes in the presence of other substances, potentially decreasing aesthetic appeal or product efficacy.1 This is a significant concern, as at-home tooth bleaching solutions are not primarily comprised of their active chemicals; water makes up the largest portion of any solution and mineral deposits in that water can cause a color change when exposed to peroxides and other bleaching agents. Hydrogen peroxide, in particular, is unstable and as such, there is a wide range of minerals which will react poorly with it. These minerals, such as iron, copper, bronze, chromium, zinc, lead, manganese, chloride and silver, are commonly found in water. Even in trace amounts, such minerals have the potential to react poorly with the hydrogen, causing the solution to change color and become less effective.2 Using demineralized water doesn’t entirely guarantee there will be no minerals impacting the hydrogen peroxide in your solution. For example, a small amount of hydrogen peroxide mixed with iron can cause the color of the solution to shift, creating a subtle, unappealing yellow or brownish tint.
In the past, the hydrogen peroxide was kept in a separate tube, which was only combined with the other ingredients once the consumer was ready to use the product. This reduced the risk of unappealing color changes and ensured the product remained stable. Advances in bleaching chemistry, such as the development of solid bleaching agents, have changed this practice and active ingredients no longer have to be kept separate, as chemical reactions are delayed. However, with these advances come the increased risk of an unappealing color result or reduced effectiveness of product due to chemical combinations.3 When the color of a solution changes, this could be an indicator that an undesired chemical reaction has occurred. In addition to color change, hard minerals like calcium and salt have the potential to turn a clear solution cloudy. This haze is another indicator that an unwanted chemical reaction has occurred in your solution and may cause customers to question the quality of the product.
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