Baking soda won't work either. Trust me, the only way is to get them re-done. You must have gotten resin instead of porcelain, because porcelain won't turn yellow. Resin costs $50-100 per tooth, porcelain costs $200-1000 per tooth, depending on where you get it done.So a lot of people get resin because it's cheaper, and it does stain where porcelain does NOT stain. ALL bonds, even porcelain, need replaced after 10-15 years, so you are probably due for replacement by now. I've had mine for 9 years, so I'm waiting for them to start having problems or coming off or something. It's going to cost me a fortune to replace the porcelain. I have eight teeth bonded, all my front teeth. It's the price we pay for beauty!!