Tooth Whitening
Whitening toothpastes function by removing surface stains to reveal the natural appearance of the underlying enamel. The main types of agent that have been included in whitening toothpastes to remove stain are listed below with their proposed modes of action:
- Physical cleaners: insoluble abrasive particles that abrade away stained pellicle on the surface of the tooth. [Barbakow et al, 1987; White, 2001]
- Surfactants: amphiphilic molecules that solubilize the organic matrix of the stained pellicle, facilitating the action of the abrasive. [Barbakow et al, 1987; White, 2001]
- Polyphosphates: mild calcium chelating agents with high affinity for enamel surfaces can reduce the amount of adsorbed pellicle to which stains are bound, and they can reduce pellicle mineralization. [Yankell et al, 1995; Tantbirojn and Douglas, 1998; Grossman et al, 1987; Yankell et al, 1999]
- Bleaches: strong oxidizing agents that chemically alter stain molecules, degrading them or causing them to lose their ability to absorb radiation in the visible region. [Nathoo and Gaffar, 1995]
- Lytic enzymes: agents which digest the organic matrix (protein or carbohydrate) of the pellicle. [White, 2001]
Of these treatments, only bleaches (such as peroxide) have been shown to penetrate the enamel surface to remove subsurface stains. Peroxide requires extended time to bleach effectively, and its lack of oral substantivity and the presence of efficient peroxide-degrading enzymes in pellicle means contact time with the tooth surface is very short in vivo. [Nathoo and Gaffar,1995]
The efficacy of lytic enzymes is similarly uncertain as they also take time to act and are not orally substantive.
Whitening toothpastes most commonly achieve superior stain control performance through use of a more effective abrasive system and/or incorporation of polyphosphates.
