Thanks for writing your query.
Chewing gums are not related to teeth whitening.
If your teeth are discoloured,i would suggest you visit a dentist
in your area and get the scaling done,if after scaling you have stains there are various options for teeth whitening according to your situation like bleaching/veneering/porcelain crown etc.....
If you need instant whitening you can opt for zoom bleaching,it gives instant teeth whitening but it is expensive(15-20 thousand).
Use mouth wash for 15 day,maintain good oral hygiene
,brush twice daily and rinse your mouth after each meal,biannual dental visits and scaling (if needed).
Hope this will be helpful.
Dr. Gunjan Gupta