“Life is like a mirror—smile at it and it smiles back at you.”

The above quote is one of dozens that extoll the power of smiling. Quotes about smiling tend to emphasize how it can boost confidence, enhance communication, help make friends, improve your mood, and otherwise confer positive benefits.

You probably won’t be surprised to learn that people have sought ways to whiten their teeth since ancient times. Ancient Egyptians used a whitening paste of ground pumice and wine vinegar, while ancient Romans whitened their teeth by rinsing with urine, with its ammonia serving as a bleaching agent. Along with these tried and surprisingly true teeth whitening efforts, the ancients probably experimented with other whitening methodologies that weren’t passed down through history due to their lack of success.

Success in one’s personal and professional life is often driven by confidence, which in turn tends to be influenced by one’s self-esteem. However, confidence-spurring self-esteem can be compromised by one’s self-image, particularly over concerns about their smile. As noted, 17th-century naturalist John Ray said, “Beauty is power; a smile its sword.”