When brushing your teeth with baking soda the baking soda can remove some teeth stains that are just small teeth stains.
But if you have severe teeth stains or your teeth are really stained and not as white as before then just plain baking soda won't likely whiten your teeth completely.
If you want to naturally whiten your teeth with baking soda you can use some hydrogen peroxide along with the baking soda to help clean your teeth and whiten your teeth.
Still some teeth stains may require professional cleaning to get your teeth whitened but sometimes baking soda and hydrogen peroxide will whiten your teeth.
It's best to keep whitening your teeth often and clean your teeth often using baking soda, hydrogen peroxide etc or teeth whitening strips before the teeth get too stained or discolored.