Use of shade guides for color measurement in tooth-bleaching studies

Several different methods are used to measure tooth color in bleaching studies. The ADA Acceptance Program Guidelines for Home Use Tooth Whitening Products specify the use of a value-oriented shade guide and/or electronic color measurement devices. Since people perceive color differently, shade guides are a subjective measure. Differences between raters and by the same rater are well documented in the dental literature. The purposes of this article will be to discuss the advantages and disadvantages using shade guides to measure color change related to tooth whitening, and to evaluate the correlation of data gathered from the use of shade guides to electronic color measurement devices. Using an order published by the manufacturer, both the TRUBYTE Bioform and Vita Classical guides can be arranged by value. A study by O'Brien demonstrated however, that the order is flawed and the change in brightness from tab to tab varies greatly. Despite these disadvantages, a review of data from several clinical trials demonstrates that Vita Classical shade guide data is consistent with data gathered using electronic color measurements. Furthermore, the O'Brien data can be used to make both these guides better measurement systems. The ADA Certification program standards define the degree of overall color change that should be considered clinically important. This issue is as critical as the measurement system used. Reporting color changes that are neither detectable to the human eye nor considered by the public to be important offers the profession little usable information. Given that any standard for color change during bleaching must relate to the abilities of the human eye, it is the conclusion of the author that shade guides should remain a critical element of any bleaching study.

Clinicians are frequently exposed to reports of bleaching agents that have been shown to result in a change of 6, 7, 8, etc., tabs. Without understanding the limitations of the shade guide used, reports of a specific shade tab change are of little use and may actually be misleading.