Activated Charcoal Dental Products: Evidence of Effectiveness Is Lacking

Notably, the US Food and Drug Administration does not regulate oral products marketed as cleaners or whiteners, such as these activated charcoal-based products. These products are considered cosmetic, and this should be an alert to both practitioners and patients.³ With patients having easy access to and increased interest in these products due to growing publicity-despite a relative lack of knowledge about them-dental professionals may be inclined to indicate them without fully knowing the possible benefits and side effects.^1,4 Moreover, the literature that supports the use of activated charcoal-based products for various applications in daily dental activity is still being generated.

This article, therefore, is aimed at helping clinicians enhance their knowledge on this topic by presenting the principles and mechanism of action of activated charcoal-based oral care products and showing the evidence supporting their use. The literature on charcoal products was searched using MEDLINE and the Cochrane Central Registry of Controlled Trials, with articles from 1955 to August 2021. The search terms used were "charcoal," "oral," and "dental." The best-quality evidence (eg, meta-analyses, systematic reviews) received the greatest emphasis.

While charcoal is a popular and efficient component for treating poisoning and drug overdose,⁵ is used in water purification, and is a common ingredient in foods in some cultures,¹ it was first reported as an oral hygiene product by Hippocrates,⁶ and culturally many populations still use it.¹ In dentistry today, manufacturers are commercializing dentifrices, mouthwashes, and toothbrushes with bristles containing activated charcoal, advocating the use of charcoal to treat halitosis, remove extrinsic stains, and enhance tooth whitening via a completely natural product.

According to Greenwall et al, the charcoal used is typically a fine powder form of activated charcoal that may be made from nutshells, coconut husks, bamboo, and other carbon-rich sources. The charcoal has been oxidized by controlled reheating or chemical means, presenting variable abrasivity depending on the source and methods used to prepare and mill the charcoal.⁷ However, other than the fact that activated charcoal is a fine powder, information on the size of particles is lacking in the literature.

Regarding its mechanism of action, the aforementioned authors also suggested that activated charcoal binds to surface deposits, holding plaque and other pigments in the pores of charcoal, which may be brushed away.⁷ Some antimicrobial activity by activated charcoal has been advocated as well. Activated charcoal reportedly could remove bacteria from water systems by attaching microorganisms to activated charcoal through strong van der Waals forces.⁸ A laboratory study by Thamke et al evaluated the antimicrobial efficacy of charcoal bristles in toothbrushes.⁸ The authors reported a significant reduction in bacterial counts and fewer colony forming units in charcoal bristles compared with regular toothbrushes. Conversely, another recent laboratory study that evaluated the antimicrobial potential of charcoal-based dentifrices failed to show potential inhibition of Streptococcus mutans biofilm growth.⁹ To date, no clinical studies have been conducted to evaluate the antimicrobial efficacy of charcoal-based dental products on the prevalence/occurrence of caries or gingivitis. The present authors, therefore, cannot state that charcoal toothbrushes can prevent biofilm-mediated diseases, such as caries and gingivitis.

Another important observation is the absence of fluoride in many activated charcoal-based oral care products, especially dentifrices. Because such dentifrices claim to be "natural" products, manufacturers often do not include fluoride in their formulation, and this can compromise the prevention of tooth decay.^5,10 Even in those activated charcoal-based dentifrices that do present fluoride, there is a concern regarding the fluoride release as it is believed that activated charcoal could adsorb the fluoride, reducing its availability in the mouth.⁷ Also, the abrasivity of activated charcoal-based products and associated potential tooth wear has been questioned in the literature.^2,7

A literature review by Brooks et al on charcoal-based dentifrices stated that only 8% of the products contained fluoride.¹ Another review stated that fluoride was present in 13.9% of the charcoal-based mouthwashes studied in the literature.¹¹ The concentration of available fluoride in these products is also a concern. Because of charcoal's good adsorptive capacity^5,12-it was even used to reduce the fluoride concentration in the water of some communities that presented high risk of fluorosis development¹³-adding charcoal to any formulation, eg, toothpastes, mouthwashes, etc, may reduce the amount of fluoride available in the mouth to prevent caries.

In a laboratory study, Panariello et al compared charcoal-based dentifrices with regular dentifrices, both with or without fluoride.⁹ The authors concluded that no charcoal-based dentifrices showed anticaries potential when compared to regular fluoride-containing dentifrices. Therefore, with fluoride being a cariogenic inhibitor, this information raises concerns about charcoal-based products being able to provide adequate protection against enamel demineralization and tooth decay development.

Regarding whitening potential, insufficient evidence exists for charcoal-based dentifrices.¹ Greenwall et al suggested that due to the high adsorbance of charcoal, there are no free radicals of whitening agents available to reduce intrinsic stains.⁷ Also, charcoal particles may lead to marginal staining, compromising restoration esthetics. Consideration must also be given to the correlation between the whitening claims of these dentifrices and their abrasivity. De Lima et al showed that whitening dentifrices do not abrade more than brushing with saliva.¹⁴ However, even though activated charcoal particles are fine and their abrasivity depends on the source and preparation method as previously stated,⁷ some attention was given regarding the abrasive potential of charcoal-based dentifrices.

Viana et al conducted a laboratory study that evaluated the abrasive potential of charcoal-based toothpastes associated with an erosive challenge.² The authors concluded that charcoal-based toothpastes did not enhance tooth wear of eroded dental tissues. Osmanaj et al concluded that charcoal-based toothpastes had little influence on the abrasion of tooth structures, but some attention should be given when brushing exposed dentin surfaces.¹⁵ Other studies also did not find differences on enamel surface roughness when brushed with charcoal-based dentifrices, regular fluoridated dentifrices, or whitening toothpastes.^5,10 On the other hand, studies conducted by ElAziz et al and Koc Vural et al found that charcoal-based whitening toothpastes could increase surface roughness, raising concern of biofilm accumulation. Both of these studies also concluded that no clinical acceptable whitening effect could be achieved.^16,17 A toothbrushing simulation study showed that charcoal-based dentifrices affect the gloss and color stability of ceramics earlier than a regular toothpaste.¹⁸ The authors raised concern about recommending charcoal-based dentifrices to patients that present with restorative work due to the abrasive potential of these products on ceramics.

The literature is scarce on scientific information about the influence of charcoal-based dental products on gingival health. According to Brooks et al, there is no evidence that charcoal-based mouthwashes could improve gingival or periodontium health.¹¹ In fact, there also are no clinical studies showing the effectivity of charcoal-based dental products for management of halitosis. Additionally, Greenwall et al made an observation regarding the pigmentation of the tongue, marginal defects of restorations, and toothbrush bristles with the use of charcoal-based dentifrices.⁷ The authors postulated that patients may extend their brushing time to remove this pigmentation, and sometimes restorations may be stained by the accumulation of charcoal particles in cavosurface margins, deep fissures, and other surface defects. This condition may lead patients to resort to restoration work due to the compromise of esthetics. Furthermore, the authors reported that the bristles of the toothbrush may acquire a grayish aspect that resists rinsing and raises the hypothesis that this may be a reason for the commercialization of black-bristled toothbrushes for use with charcoal-based products.

Despite charcoal-based oral care products gaining popularity, the literature regarding evidence to support them for oral health is still scarce. However, frequent advertising and society's push for natural products compels patients to inquire of their dentists about these items. Thus, it is important for clinicians to be aware of current evidence.

In vitro studies have shown that charcoal can absorb fluoride and reduce its availability and concentration, and thus its anticaries effectiveness.⁹ In addition, as discussed, charcoal toothpastes and mouthwashes may have less or even no fluoride compared to regular products. Clinicians, therefore, should instruct their patients in the evidence that is available and avoid prescribing these products for patients with a history of dental caries. In addition, although the claim that charcoal has antimicrobial properties is widely disseminated, no clinical study supports this assertion nor this possible effect on, for instance, the prevention and treatment of gingivitis.

Within the limits of the available literature, charcoal-based products should be prescribed with extreme caution. More evidence is needed to elucidate the real potential of charcoal products for oral health, as well as their side effects. In addition, little or no scientific-based information was found to prove their potential benefits.

Ingrid Fernandes Mathias-Santamaria, DDS, MS, PhD
Clinical Assistant Professor, Division of Operative Dentistry, Department of General Dentistry, and PhD Program in Dental Biomedical Sciences, University of Maryland School of Dentistry, Baltimore, Maryland

Joyce P. Huey, DDS, MEd
Assistant Professor, Division of Operative Dentistry, Department of General Dentistry, University of Maryland School of Dentistry, Baltimore, Maryland; Fellow, International College of Dentists

Howard E. Strassler, DMD
Professor, Division of Operative Dentistry, Department of General Dentistry, University of Maryland School of Dentistry, Baltimore, Maryland; Fellow, Academy of Dental Materials; Fellow, Academy of General Dentistry

Mary Anne Melo, DDS, MSc, PhD
Interim Department Chair, Associate Professor, Director of Operative Dentistry, Department of General Dentistry, and PhD Program in Dental Biomedical Sciences, University of Maryland School of Dentistry, Baltimore, Maryland; Fellow, Academy of Dental Materials