I’ve been using the Colgate Optic White Oxygen toothpaste and Optic White Overnight whitening pen for nearly a month and the difference is amazing! After 3 days I already saw a difference and experienced no sensitivity. The overnight whitening pen is also very easy to use with no aftertaste or weird feeling. You have to use the products consistently to see a difference, but super happy with my results and this is definitely a home staple product.