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The Science of Teeth Whitening

Science of Teeth Whitening
Get details on whitening right here.

For the full story, download our PDF, 3D Whitening:
The Science Behind a White, Bright, and Beautiful Smile.

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 Stains

Stain 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 Tooth Surface

To 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.

The Biology of Tooth Color and Tooth Stains

To understand the dynamics of tooth color, one must start with two interrelated concepts: the biological mechanism that leads to tooth discoloration and stain formation.

Tooth color is the inherent color of the tooth as perceived by others. It is determined by the transparency of the enamel, the color tone of the underlying dentin and any imbedded staining contained between the dentin and the enamel surface. (8,11) It is also associated with the light scattering and absorption properties of the enamel and dentin. Enamel is a quasi-translucent structure which allows the underlying yellowish dentin color to show through. (11)

Stain formation: Researchers have identified many factors that can lead to tooth discoloration and staining, such as bad oral hygiene, dietary considerations (tannins), tobacco usage (tar), medical history and aging. (12,13) Tooth stain formation can be classified based on the stains location relative to the enamel:

Extrinsic stains are located in the tooth pellicle, the tenacious organic film made up of proteins commonly found in saliva that covers the enamel. Pellicle can become stained as a result of daily food consumption and the chromogens, or pigments, contained in food, tobacco and beverages. This film can be cleaned away through dental cleaning and chemical treatments, such as brushing with whitening toothpaste.

Intrinsic stains are located beneath the enamel surface. Overtime, chromagenic materials diffuse into the enamel and accumulate at the dentin level and within the enamel. Aging is the primary cause of intrinsic stains. Other possible causes include taking certain medications and eating and drinking foods and beverages that stain over a long period of time. Generally, the only way to eliminate these stains is by bleaching techniques or using professional or at-home whitening procedures.

Stain particles from food, drink and/or tobacco build-up on tooth enamel. Some stain particles stay trapped in the outer layer of the tooth, while over time others work their way through the enamel. Stain particles that settle beneath the tooth surface make teeth look yellow and dull.

How White is White?: Color Measurement

Color 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
significance.(17)

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.

Sources

8. Joiner A. Tooth colour: a review of the literature. Journal of Dentistry 2004; 32: 3 12

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

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