Healthy teeth are generally a little yellow, because they are human bones, and yellow is not so white. If it is very white, it means that it is either a porcelain tooth or it has been treated in some way and is not a normal tooth. The most important thing for us to protect our teeth is to brush our teeth and clean our mouth at ordinary times, and then keep the elements fully supplemented.
Don't walk away just because your teeth are a little yellow. Too much cleaning of dead porcelain will actually do great harm to our teeth. It's no problem to protect them more at ordinary times.