Yellow film on teeth of a person in their 30s is not so bad. First of all, it is important to remember that everyone's teeth have different shades to them. Some people have a yellow shade while others have a grey shade. The good news is that teeth with yellow shades are the ones that have the best results. Secondly, in order to remove the yellow film we must know what we are dealing with. Stains are usually classified as extrinsic (outside the enamel) or intrinsic (inside the enamel). Stains that are extrinsic may be able to be brushed off; however, a lot of them need to be removed by a dentist with different instruments (hand instruments, ultrasonic scalers, etc.) or possibility of bleaching. The best way to get rid of the yellow staining is to get an evaluation by a dentist to know what it is and how to removed it. Hope this helps.
My best to you!
William F. Scott IV, DMD
Please consult with your dentist on your concern of your teeth. You can try changing some habits like drinking coffee from a straw or you can look into whitening options.
Thank you for your question.