Answered by Shaykh Shuaib Ally
Question: Is it permissible to use charcoal (of wood) / charcoal (of wood) derivative as an ingredient for a tooth whitening powder?
Answer: Assalamu ‘alaykum,
I pray that you are well.
You can use anything to whiten your teeth that does not cause bodily harm, or is not itself impure.
If the items you have mentioned fit that description, there is nothing preventing their usage.
God knows best.