In 1636, Delights for Ladies by Sir Hugh Plat has a recipe for making teeth whiter.

To keepe the teeth both white and sound. Take a quart of hony, as much Vinegar, and halfe so much white wine, boyle them together and wash your teeth therwith now and then

Also, the Romans were known to use urine - sometimes- to whiten their teeth. I forget who wrote the poem, but I recall one famous orator writing about another gentleman who was so vain and showed off his pearly whites that the orator basically said "Yes, we know you have perfect white teeth because we also know you wash them in urine!" I wish I could recall the actual words but it was along those lines.

Edit: The Roman I couldn't recall was Catullus. The poem is really funny in Latin.