Can toothpaste intrinsically whiten your teeth?

It should not be underestimated how a white radiant smile can affect our self-esteem and confidence. It is worthwhile to know how to effectively maintain a whiter more radiant smile.

To do this it helps to know the different causes of tooth discolouration, there may be more than you expect. The causes of tooth discolouration can be categorised as extrinsic, which are surface stains that occur either, directly due to chromogens in the foods that we consume (e.g. coffee, tea, and wine) or indirectly due to chemical reactions that take place in the mouth (chlorhexidine mouth wash and tea) [1]. The other category of discolouration is intrinsic, which is due to physical changes in your teeth, for example, this can be due to thinning of the enamel due to ageing (local cause), or due to medications or metabolic disorders (systemic causes) [2].

Dental practitioners typically follow a hierarchy system, starting with the least invasive treatment options to address a patient’s tooth discolouration [2]. This is because higher-tier professional whitening treatments, although more effective, are associated with increased risks of biological side effects [3]. The full extent of these treatment options is beyond the scope of this article; therefore, we will look at the least invasive and most accessible form of tooth whitening – at-home oral hygiene/care.

There are various types of whitening toothpaste on the market, many of which you have likely encountered, tried, or might have considered using. Let’s look at how they work and determine whether they remove extrinsic surface stains or if they are able to intrinsically change the colour of your teeth.

Over-the-counter whitening toothpastes

Abrasive agents

Whitening toothpastes are typically designed to remove and prevent the accumulation of extrinsic surface stains with abrasive agents [1]. During tooth brushing, abrasive particles in whitening toothpaste become lodged between the toothbrush bristles and the stained tooth surface. These particles, being harder than the extrinsic stains, effectively dislodge and remove the stain. This mechanical action is specifically effective against extrinsic stains—those located on the outer enamel layer—and does not significantly impact the tooth’s natural shade [1]. Specialized abrasive systems remain the most common approach for tooth whitening in today’s whitening toothpastes. It is worth noting that highly abrasive whitening toothpaste may negatively impact the integrity of the enamel and may not be appropriate for children or individuals with worn enamel, erosion or exposed dentine [3,4].

Activated Charcoal

In recent years, activated charcoal has garnered significant attention as a natural ingredient in oral care products, particularly whitening toothpastes. Activated charcoal has a high surface area and may assist in tooth whitening by absorbing pigments, chromophores, and surface stains [3]. Like most traditional whitening toothpaste, its whitening effect mainly achieved through abrasion to mechanically remove extrinsic surface stains [5]. With this being said, the use of activated charcoal products is strongly discouraged by dental professionals and scientific literature due to the risk of abrading the enamel causing surface roughness, in more severe cases sensitivity [6].

Chemical agents

Whitening toothpaste may be formulated not only with abrasive agents to physically remove surface stains but also with additional chemical components that enhance their stain-removal efficacy. These chemical agents work synergistically with abrasives to aid in the removal and prevention of extrinsic stains. Examples of commonly used chemical agents are peroxides (hydrogen peroxide and carbamide peroxide) and enzymes [1].

Apart from assisting abrasives in removing extrinsic surface stains, chemical agents such as peroxides are capable of intrinsically altering tooth colour. Peroxides oxidize the organic matrix of the enamel, which transforms the transparent enamel proteins into a more opaque, whiter material, leading to a noticeable alteration in tooth colour [7]. While peroxides are recognized for their ability to intrinsically whiten teeth, their greatest effectiveness is demonstrated in delivery formats such as trays, strips, and paint-on applications. This is due to longer contact times with the tooth surface. In contrast, toothpastes offer relatively shorter exposure times, which can limit the whitening potential of peroxides [1].

A significant concern with whitening toothpastes containing peroxides, such as hydrogen peroxide, is that they typically have a low pH, usually below 5, which is notably more acidic than regular toothpastes. This acidity can be detrimental to dental hard tissues such as enamel and dentine, as it may cause erosion. This can result in permanent damage, increased sensitivity, and a greater susceptibility to fractures [8].

Optical modifying agents

You may have seen purple toothpaste, also referred to as a colour corrector or a tooth toner, trending on social media due to its immediate whitening effect. These toothpastes contain an optical modifying agent, a pigment called blue covarine. Optical modifying agents in toothpaste may also intrinsically alter tooth colour, except this is achieved by enhancing the perceived whiteness of teeth through visual effects rather than chemical alteration of tooth structure.

Blue covarine functions by depositing a thin, semi-transparent blue film onto the tooth surface during brushing. This film alters the way light reflects off the teeth, shifting the colour perception from yellow towards blue, which the human eye interprets as whiter and brighter teeth. This optical effect provides an immediate, though temporary, improvement in tooth whiteness without chemically changing the tooth enamel [3,9].

Important considerations:

• Temporary Effect: The optical whitening is not permanent and diminishes as the blue film wears off [3].
• Variability in Efficacy: The effectiveness can vary based on individual factors, including the presence of the acquired pellicle, which is necessary for the blue film to adhere properly [3].
• Interaction with Other Agents: The presence of other substances, such as activated charcoal in some toothpastes, may adsorb the blue pigment, potentially reducing the whitening effect [3].

In ingredient lists, blue covarine is typically listed by its Colour Index (CI) number, which is CI42090.

Nano-hydroxyapatite

According to literature, nano-hydroxyapatite is a biomimetic mineral, that can immediately improve the appearance of your teeth, and through continuous use it can create a long-lasting whitening effect. Its whitening effect is achieved through its ability to restore and enhance the natural structure of enamel, this means that is amongst the whitening toothpaste that can whiten teeth intrinsically [10].

How does it work?

• Filling Microcracks and Surface Defects: Nano-hydroxyapatite particles adhere to the enamel surface, filling in microcracks and defects. This repair process enhances the enamel’s smoothness and lustre, contributing to a whiter appearance [10].
• Remineralization: Some nano-hydroxyapatite particles dissociate into calcium and phosphate ions, which penetrate the enamel to remineralize demineralized areas. This process strengthens the enamel and restores its natural translucency [10].
• Formation of a White Opaque Enamel Layer: With prolonged use, nano-hydroxyapatite can form a new white, opaque enamel layer on the tooth’s surface. This layer reflects light, masking the underlying yellowish dentin and making teeth appear whiter [10].
• Stain Prevention: Nano-hydroxyapatite particles bind to plaque bacteria, reducing their accumulation and preventing biofilms from forming that capture chromogens and create new stains [10].

The whitening efficacy of nano-hydroxyapatite in toothpaste has been shown to be dose-dependent, with a concentration of 10% being more effective than lower concentrations  [4]. There is a vast number of toothpastes on the market that contain nano-hydroxyapatite concentrations as low as 1%, if your goal is to whiten your teeth with nano-hydroxyapatite, then make sure that you are using a toothpaste that contains at least 10%.

“Nano-hydroxyapatite could be added to commercial toothpastes at a concentration of up to 10%, as this concentration showed visually perceptible tooth whitening performance in our study while being considered biologically safe.” – Shang et al. (2022) [4]

Conclusion

Traditionally, whitening toothpastes have relied on abrasive agents to remove extrinsic surface stains, and this method remains the most prevalent approach today. However, such abrasive formulations may not be suitable for everyone, particularly individuals with worn or thinning enamel, as they can exacerbate sensitivity or enamel erosion.

To address these concerns and enhance whitening efficacy, modern toothpastes have incorporated additional agents that target intrinsic discolouration. These include chemical agents like peroxides, optical modifiers such as blue covarine pigment, and biomimetic compounds like nano-hydroxyapatite.

Among these, nano-hydroxyapatite stands out due to its dual benefits for both aesthetics and oral health. As a compound that closely resembles the natural mineral component of tooth enamel, nano-hydroxyapatite can integrate into the enamel structure, filling microcracks and surface defects. This not only enhances the tooth’s appearance by creating a smoother, whiter surface but also strengthens enamel and reverses the precursors of cavities.

To answer the question in the title, yes, there are toothpastes designed to intrinsically whiten your teeth. We believe nano-hydroxyapatite is the best among them for preserving a natural whiter smiler for a lifetime.