Charcoal toothpaste is often considered the healthiest alternative to toothpaste, and many countries offer them for free, though in many cases, the price of the product can be higher than the price you pay for a toothpaste.
In recent years, the use of charcoal toothpaste has risen in the US, Japan, France and Italy.
But in some countries, such as France, the industry is facing competition from a growing trend of using herbal toothpastes to whiten teeth.
In some countries including the UK, India and the United States, charcoal toothpastas are also sold as herbal toothpaste by some dentists.
A recent study in the journal PLOS One suggested that the use and prices of charcoal mouthwashes, while still relatively low, are rising faster than the overall price of toothpaste or dentures, and have a potential to affect global consumer spending patterns.
The authors of the study said that although the price difference between the two products is negligible, the rising demand could lead to the emergence of alternative products.
The researchers said that while it was unclear whether charcoal toothbrushes would become more popular in the future, they did note that the popularity of herbal toothbrushing is not the only factor that is affecting toothbrush prices.
A study by the International Institute for Sustainable Development in Beijing found that in China, the average cost of charcoal was around 60 cents per litre, compared to around 25 cents per liter for toothpaste and around 13 cents per toothbrush.
Other studies have also suggested that herbal toothbrush prices are rising.
In a recent study published in the New England Journal of Medicine, researchers looked at the price differences between herbal and conventional toothbrushed products and found that while the price per litres of conventional toothpaste fell in 2014 and 2015, the amount of money spent on the herbal toothwash increased.