Hello Blackish stains can be due to intake of multivitamins. There is no other option than removing it as they are very hard

Hello Can you elaborate what blackness are you mentioning? If you can share pictures that would us guide you better.

The blackness on the back side of your teeth, especially between the teeth, is usually due to plaque or tartar (calculus) buildup and staining. This area is difficult to clean properly, so deposits can accumulate over time. It is advisable to get a professional cleaning (scaling) done by a dentist. Also, maintain good oral hygiene—brush twice daily, floss regularly, and rinse your mouth after meals. If you notice sensitivity, bleeding gums, or bad breath, please visit a dentist for a proper check-up.

Hello The blacklist which is deposits on the teeth are formed due to improper oral hygiene You need to brush your teeth in the right direction