Designed to be used with custom trays your dental professional created for you, the Natural Elegance Plus At-Home Tooth Whitening Refill Kit is a carbamide peroxide tooth whitening kit that contains potassium nitrate and fluoride. Made of a neutral pH, it reportedly reduces patient sensitivity and is kind to enamel. The water-based formulation is designed to keep teeth hydrated for reduced sensitivity. The fluoride is said to allow for anti-caries benefits, an increase in enamel micro-hardness and improvements to overall enamel health. Although we use a special non-sensitive urea amide peroxide formula in the tooth whitening gel, and generally it has a good tolerance for all healthy teeth, but sometimes sensitivity occurs. Not suitable for use in children under 12 years of age. If you have very sensitive teeth, or have any type of dental disease, gum disease, such as caries, ulcers, etc., please do not use. If necessary, consult a medical professional. If you are pregnant, breastfeeding or have any dental or gum problems; If there is any irritation, sensitivity, please stop using and consult a medical professional