Not only do you risk overdose, several other risks of using charcoal toothpaste have been brought forward. The biggest concerns include:
Abrasiveness. Used regularly charcoal can damage tooth enamel and gum tissue.
Over-absorption. Charcoal may absorb beneficial items such as needed medications.
Constipation. Intestinal blockages and constipation can be a result of long term use of charcoal, in addition to black stools and a discolored tongue.
After effects. Even those who love charcoal toothpaste report needing to use regular toothpaste after a charcoal treatment to rinse it away and give fresh breath, otherwise a black residue may remain
No fluoride. Charcoal toothpaste can’t be used in place of regular toothpaste as it doesn’t contain the necessary component of fluoride, which fights dental decay. “Fluoride is nature’s cavity fighter and can cut tooth decay by up to 40 percent.” Source: Daily Burn
Unknown safety. There are few studies on the benefits of charcoal as a dietary supplement, so both short and long-term effects are unknown.
Unknown effectiveness. Charcoal’s whitening effect is largely speculative. There have been no scientifically accepted studies that confirm charcoal’s whitening claims.