A lot has come into question about how abrasive activated charcoal is. This is a great question to ask of any toothpaste or oral hygiene product. And unless it has been tested it is hard to say. In dentistry we have a measure called Relative Dentin Abrasivity (RDA), which indicates how abrasive a product is.
Some of the best selling toothpastes on the market have high RDA values. When RDA values are 200 or more, the toothpaste can be too abrasive for daily use and can have negative effects on your teeth. A large problem with activated charcoal products is that they either don't have tested RDA values or if they do, they are not advertised. Therefore we really don't know if many products out there are too abrasive or not.
On top of RDA values there are other factors that you need to consider, such as how long or how many times a day your are brushing, amount of toothpaste being used, brushing force, or even what kind of bristles you have on your toothbrush (i.e. soft, medium, hard). With all that being said activated charcoal can be a great product as long as it is in a safe form. It's a great stain remover, but also a great odor adorber, helping to combat bad breath in the mouth.
White Birch Whitening Toothpaste has been tested to be 45 on the RDA scale, making it 50% less abrasive than Colgate Optic White (RDA 100). Another great thing is that White Birch is made with WHITE activated charcoal (NOT BLACK, like all the others on the market today). No more messy sinks!