One of the important duties fulfilled by members of the ADA's Dental Instruments & Material Equipment (DIME) committee is to keep abreast of and interpret the many studies and learned articles published within the dental community. Here, committee member Dr Chris Callahan provides an overview of an informative paper, recently reviewed.
Much work has been done on validating therapeutic agents used in oral hygiene. There is ongoing public interest in charcoal-based products for general health care. Charcoal has been used in toothpaste, mouthwash, toothbrush bristles, floss, tooth whitening strips and even chewing gum. This 2020 literature review article in the British Dental Journal by John K. Brooks, Nasir Bashirelahi, Ru-ching Hsia and Mark A. Reynolds examined the available research on charcoal-based mouthwashes. A significant reference list provides a broad resource for the current uses of charcoal in dental products.
The paper's aim was to review any clinical and laboratory evidence that the use of charcoal mouthwashes reduces gingival inflammation, promotes tooth whitening, or causes any adverse effects. Inclusion criteria proposed was clinical trials with a minimum of six months follow up. Active ingredients in products were assessed by reading product labels and documentation.
Results
Ten clinical articles were identified as being found by MEDLINE and Scopus search. Unfortunately, no studies met the inclusion criteria.
Product ingredients
Thirty-six products were found containing charcoal- based active ingredients. Other therapeutic ingredients found were fluoride 5/36, xylitol 5/36, chlorhexidine or cetylpiridinium chloride 3/36. Alcohol was present in 3/36. Oils including tea tree, peppermint, limonene, thymol and menthol were also included. Glycerin 7/36, and Coconut oil 17/36 were provided as possible lubricating agents.
Hydrogen peroxide was found in one product.
Beneficial effects
At the time of publication, clinical or laboratory-based research had not demonstrated any therapeutic benefit for any criteria. The following observations were made on possible justification for use of charcoal in dental products.
Laboratory studies have shown some antimicrobial properties for charcoal as a powder or toothbrush bristle coating.
The presence of charcoal may well reduce available fluoride where included in products such as toothpaste or mouthwash. Charcoal has been used at a community level to reduce fluoride levels in water supplies.
Systemic charcoal administration reduces halitosis to a limited degree in trimethylaminuria. This has not been demonstrated with use of mouthwash.
Neither glycerin or coconut oil have been demonstrated to provide any effect against xerostomia.
The whitening effect of charcoal has been debated. Marginal staining may arise on restorations. One in vitro study found slight improvement in surface staining. Largely the effect would seem to be inconclusive.
Adverse reactions
Of the polycyclic aromatic hydrocarbons present in charcoal, four of 15 are considered carcinogenic. This is of concern where mouthwashes containing oils were advocated for the longer time exposure procedure of 'oil pulling'. Consensus has not been reached about the inclusion of alcohol in charcoal-based mouthwashes.
At least two of the mouthwashes were described in documentation as being abrasive. Some level of abrasive effect has also been demonstrated in toothpastes.
In summary, no positive evidence has been found to support the inclusion of charcoal in mouthwash. While an article such as this would seem to be disappointing to some, the disproving of a theory is a necessary and significant scientific process.
