Hello,
There is nothing as best toothpaste but most recommended are the toothpaste with fluoride.
For white teeth see yellow colour is considered normal to people of Asia though you not satisfied you can go for bleaching.
If you have canker sores each month it clearly indicates you have
vitamin deficiency, take vitamin B capsule for it... Please tell us does your canker sores is painful??
For healthy teeth brush twice daily, do warm saline rinse 3 to 4 times a day
Next Steps
get your RCT done apas