Charcoal Toothpaste Has Entered the Composite Chat

Charcoal toothpaste has the personality of a wellness product that has wandered into dentistry wearing excellent marketing and very little humility. It promises purification, brightness, and a faintly apocalyptic bathroom sink. Barros and colleagues’ Surface properties and susceptibility to staining of a resin composite after brushing with different whitening toothpastes asks a more useful question: what does all this enthusiastic scrubbing do to composite resin?

The answer is not soothing. In this laboratory study, whitening toothpaste (WT) composition changed surface microhardness (SMH), surface roughness (Ra), and later coffee staining behaviour. Charcoal, in particular, did not emerge as the friend of the restoration.

The Data Anchor

The authors prepared 120 Filtek Z250 micro-hybrid resin composite specimens and divided them into six groups: distilled water, regular toothpaste, and four Colgate Luminous White formulations containing silica plus pyrophosphate, pentaphosphate plus pyrophosphate, hydrogen peroxide plus pyrophosphate, or charcoal plus pyrophosphate.

Specimens were brushed for 825 cycles, simulating 30 days of brushing, then immersed in coffee for 30 minutes daily for another 30 days. They measured colour change, SMH, and Ra at baseline, after brushing, and after coffee exposure. After toothpaste use, the charcoal group had the lowest SMH values at 70.92 ± 5.40, compared with about 82 to 87 in most other toothpaste groups. For roughness, silica plus pyrophosphate reached 0.50 ± 0.00 μm after brushing and 0.53 ± 0.01 μm after coffee; charcoal plus pyrophosphate was close behind at 0.48 ± 0.01 μm and 0.53 ± 0.01 μm.

Key Findings

• Charcoal was hardest on hardness. The charcoal toothpaste group had the lowest post-brushing SMH and differed statistically from all other groups at that time point.
• Roughness rose across the board. Every group changed over time, but silica plus pyrophosphate and charcoal plus pyrophosphate produced the highest roughness values after brushing and coffee.
• Coffee found the weakened surface. After coffee exposure, the charcoal group had the highest ΔE*ab and ΔE₀₀ colour-change values among the evaluated groups.
• The clinical warning is narrow but useful. This was in vitro, using one micro-hybrid composite, one brushing simulation, and one coffee protocol; it is not a direct prediction of every restoration in every mouth.

Whitening advice becomes rather less glamorous when the patient’s anterior composite has been recruited into the abrasion experiment at home.

💡 The Clinical Bottom Line

The gold standard here is not panic; it is specificity. If a patient has visible composite restorations and wants whitening toothpaste, the restoration surface deserves the same chairside conversation as the enamel.

This study supports a cautious line on abrasive or charcoal whitening products around composite resin. The promise of a brighter smile is less compelling when the restoration is being turned into a better coffee trap.

Dr Samuel Rosehill is a general dentist with a prosthodontic focus, practising at Ethical Dental in Coffs Harbour, NSW. He holds a BDSc (Hons) from the University of Queensland, an MBA, an MMktg, and an MClinDent in Fixed & Removable Prosthodontics (Distinction) from King’s College London.

Reference: Barros et al. Surface properties and susceptibility to staining of a resin composite after brushing with different whitening toothpastes. Restorative Dentistry and Endodontics, 2025. DOI: 10.5395/rde.2025.50.e6