hello,very good evening, first we have to find out cause's of yellow colour teeth. stain are two types external eg: tobacco, internal eg: flurosis. dentist give the treatment according to type of stain .apart from that you have to know tooth color are not white it depends upon enamel rods appear. so in my opinion you have to visit dentist -thank you.

Good evening reasons for yellow teeth are multifactorial,first is diagnosis of the type of stain, secondly according to the type,you have many options to make your tooth whiter, if it's external cleaning, bleaching will help.if internal then masking with the help of veeners is the only choice.