Hello,
These black stains occur due to following things:
1. Poor oral hygeine
2. High Caffeine diet and iron intake
3. Betel nut chewing
4. Use of excessive chlorhexidine mouthwash
5. Iron deficient anaemia
6. Chromogenic bacteria
You can rule out first 4 causes yourself. In case of 5th and 6th case, please rule out if you are iron deficient anaemic , becoz iron will be available in blood freely which causes these stains.
Chromogenic bacteria also produces
ferritin which causes stains.
Next Steps
if your condition is not resolving after regular scaling, please get your health check up done.
Health Tips
oral hygeine maintainence
avoid coffee/tea