Charcoal toothpastes: what we know so far

Charcoal toothpastes are a recent innovation in the oral healthcare product market, and some pharmacies have started stocking them. The marketing campaigns for these toothpastes are fashionable, trendy, and different to those for other toothpastes. This marketing has enjoyed considerable success, encouraging the introduction of related products, including ‘charcoal toothbrushes’, which have charcoal incorporated into the bristles.

To date, there have been no scientific studies published proving the effectiveness of charcoal toothpastes in tooth whitening, oral hygiene and any claimed preventative and halitosis-controlling effects.

Historically, charcoal, possibly together with chimney soot, was one of several materials used to clean teeth. Unlike materials such as salt, charcoal was not found to abrade teeth and had the added advantage, given its absorbent qualities, of helping to control halitosis. Charcoal is used in many countries in Africa to clean teeth because regular toothpaste in unavailable in rural communities.

Charcoal, especially when activated (i.e. combined with certain agents at high temperature) has a high absorptive capacity. In the 1990s, the World Health Organization (WHO) listed activated charcoal for the treatment of poisoning and overdoses. Activated charcoal has been promoted for many different purposes, including ‘internal cleaning’, weight loss, reducing flatulence and lowering cholesterol levels.

Charcoal toothpastes cannot be assumed to be regular toothpastes to which activated charcoal has been added. In formulating charcoal toothpastes, other agents may be added to enhance the tooth-whitening effect. Agents that help to remove dental plaque from teeth and increase the resistance of the tooth surface to carious (acid) attack, notably fluoride, may not be included because they will be absorbed by the charcoal, possibly reducing its whitening effect. Before purchasing a charcoal toothpaste, patients should consider its contents.

The effect of activated charcoal in toothpaste is a combination of relatively mild abrasion and absorption of tooth surface (extrinsic) stain. There is no evidence that the use of charcoal toothpaste has an effect on intrinsic (internal) staining of teeth or on intrinsic whitening of the teeth. The effect of charcoal in toothpaste on materials forming fillings, crowns and veneers is unknown. Charcoal-containing toothpaste may be found to be most effective when used to delay the recurrence of surface staining on teeth following professional cleaning (scaling) and polishing.

Particles of charcoal included in charcoal toothpaste may accumulate in crevices and other defects in teeth, including cracks in the teeth of older individuals. In addition, particles of charcoal may build up in gaps between dental restorations and teeth, resulting in a grey or black line around restoration margins with less than ideal adaptation. Such negative effects on dental attractiveness may necessitate the costly replacement of the affected fillings, veneers or crowns. The charcoal included in charcoal toothpastes has not been found to have negative abrasive effects. There have been some suggestions that charcoal particles left in the mouth after brushing may have certain antimicrobial effects. However, the evidence for this is weak. Charcoal-containing toothpastes are black in colour and brushing off the colour tends to prolong brushing, or the use of excessive brushing force, which may lead to the abrasion of teeth.

In conclusion, our views on charcoal toothpastes are that:

• Charcoal toothpastes may be found to help remove external (extrinsic) staining on teeth without negative abrasive effects, but the extent and rate of stain removal has not been reported.
• Individuals interested in purchasing a charcoal toothpaste should be encouraged to carefully consider the contents, or lack of certain important components, possibly fluoride, in the formulation of the paste.
• The use of charcoal toothpaste may result in negative aesthetic effects, possibly necessitating the replacement of restorations with less than ideal adaptation, which acquire grey or black marginal charcoal staining.
• Charcoal toothpastes may be found to be most effective when used to delay the recurrence of surface staining on intact teeth following professional cleaning and polishing.

Linda Greenwall

Private practitioner, London

Nairn Wilson

Emeritus professor of dentistry, King’s College London