The blackness you are seeing 6 months after cleaning is not necessarily permanent. It can be due to surface stains, plaque/tartar buildup, or a specific type of black extrinsic stain. Tea/coffee, tobacco, certain foods, iron supplements and some mouthwashes can contribute to staining.
Since you notice it between the teeth as well, I would recommend an examination to make sure it is only staining and not tartar or tooth decay. Black spots caused by decay need different treatment and cannot be removed simply by cleaning.
Next Steps
* Get the teeth examined once to identify whether it is stain, tartar or decay.
* If it is surface staining/tartar, professional cleaning and polishing can remove it.
* Brush twice daily for 2 minutes with fluoride toothpaste and clean between the teeth daily with floss/interdental brushes.
* If you drink tea/coffee frequently, rinse your mouth with water afterward.
* If you use chlorhexidine mouthwash regularly, discuss stopping it with your dentist, as it can cause brown staining with prolonged use.
Health Tips
You don’t need to completely stop all foods. Try to reduce frequent consumption of strongly staining foods/drinks such as:
* Tea and coffee
* Cola/dark-coloured beverages
* Tobacco/smoking
* Dark sauces and highly pigmented foods
These can cause extrinsic stains over time.
Also, don’t use lemon, charcoal, salt or abrasive DIY whitening methods to scrub the black areas.
If the blackness keeps returning quickly despite good oral hygiene and regular cleaning, send a clear photo of the front and inner sides of the teeth. I can help you understand whether it looks more like stain/tartar or something that needs further dental treatment.