For teeth whitening, you can use scaling. Also, if you are in the California region, I can hook you up with a very good dentist in Diamond Bar who uses an hour long session for this activity using the Zoom kit.
HI,
The colour of the teeth can change when there are plaque or tarter deposits on the teeth. Good oral hygiene, brushing and flossing are necessary. Scaling of the teeth can be done. Also you can use a whitening tooth paste. The dentist can also help you by bleaching your teeth to make them white.
The answer is based on information provided. Exact advice is not possible without a proper examination and investigations. You are requested to consult your Doctor. Take care and keep us posted.