Dip a cotton ball into the lemon juice and baking soda solution and apply it to your teeth. Let the lemon and baking soda solution sit on your teeth for around a minute. Brush your teeth to remove the acid.
Another "gel manicure" hack to try. Clean, dry nails + 1 coat of Sally Hansen Hard as Wraps Powerful Acrylic Gel (let it dry completely!) + polish of your choice coats did the trick) + 1 coat of Sally Hansen No Chip Acrylic Top Coat = Shellac fake-out!!