So How Does Teeth Whitening Really Work?Teeth whitening occurs by two means—by either acting on tooth stains on the outer layer of the tooth or below the enamel surface and/or preventing the generation of new stains. This is achieved via stain removal, stain bleaching, and stain protection.
The Removal of Surface StainsStain removal whitens teeth by using chemical and physical actions, such as abrasion, chemical stain disruption, and removal. These different actions either destroy or disrupt the stain at the top of the enamel, exposing cleaner, whiter enamel. Several whitening products base their benefits on these types of actions. For example:
- Whitening pastes contain special silica molecules that polish the enamel.
- Whitening pastes and rinses can also contain sodium hexametaphosphate (SHMP) that helps prevent the formation of future stains and disrupts the stain pellicle, facilitating its removal.
- Toothbrushes remove stains on the outer layer of the tooth by the mechanical action of the bristles on the tooth surface.
The Removal of Stains Beneath the EnamelTo remove stubborn stains that accumulate below the enamel surface, bleaching is an appropriate option. Bleaching is a chemical process in which color is eliminated by oxidation of stain molecules. The bleaching power of the different whitening products varies according to their particular concentration of hydrogen peroxide, a bleaching agent commonly used in whitening procedures at the dental office and in-home teeth whitening systems such as Crest 3D White Whitestrips.
How White is White?: Color MeasurementColor is a subjective response of the observer to the physical interaction of the object of view with light.(13) This subjectivity is seen when describing tooth color. Researchers have noted that aesthetic aspects of tooth color are difficult to quantify, making tooth color perception highly prone to individual variation.(8) Disagreement in shade matching the same tooth has been widely observed, both between professionals and when the same professional is grading the color of the same tooth at different occasions.(14)
As it is particularly important to scientifically track the success of new technologies that whiten teeth, a large body of research has been conducted to objectively measure the color of the tooth.(15)
While a variety of scales and measurement techniques have been used to assess tooth color, (8,15) some may be subjective and non-linear, making progress tracking difficult. A common method of measuring tooth color utilizes shade guides, such as the Vita Shade Guide (16) in which the tooth and the guide are observed simultaneously. The results of using this guide depend on several factors, including the observer’s experience, external light and the observer’s physiological condition.
A more successful mechanism of measuring color was developed by the Commission International de l’Eclairage (CIE), which defined a color space CIE Lab using the accepted theory of color perception based on three separate color receptors: blue (L), red (a), and green (b).(15) With this system, color differences can be objectively expressed in units that can be related to both visual perception and clinical
This methodology has been successfully applied to determine the efficacy of whitening systems by transforming digital high-resolution images of anterior dentition of the teeth taken with standard polarized lighting conditions into numerical values. The whitening benefit is defined as a decrease in b (decrease in yellowness), decrease in a (decrease in redness) and increase in L (increase in lightness).(17)
To learn more, download our PDF, 3D Whitening: The Science Behind a White, Bright, and Beautiful Smile.
11. Watts A, Addy M. Tooth discoloration and staining: a review of the literature. British Dental Journal 2001; 190: 309–316
12. Vogel R. Intrinsic and extrinsic discolouration of the dentition. A review. Journal of Oral Medicine 1975; 30: 99–104
13. Bridgeman I. The nature of light and its interaction with matter. In McDonald R, editor. Colour physics for industry. Huddersfield: H. Charlesworth & Co Ltd; 1987. p 1–34
14. Culpepper WD. A comparative study of shade-matching procedures. Journal of Prosthetic Dentistry 1970: 24:166–173
15. Miller L. Organizing colour in dentistry. Journal of American Dental Association 1987 (special issue) 26E-40E
16. Munsell AH. A color notation. Baltimore: Munsell Color Co, 1981
17. Gerlach RW, Zhou X. Vital Bleaching and Whitening Strips: Summary of Clinical Research on Effectiveness and Tolerability. Journal of Contemporary Dental Practice; 2001; 2: 1–16