The 35% Carbamide Peroxide strength whitening gel is considered a higher concentration and generally is the highest strength gel used by dentists for in-office teeth whitening. The higher strength formula whitens teeth faster and with fewer treatments than the 22% strength whitening gel. However, the user may experience increased tooth sensitivity and gum irritation, common side effects of peroxide based teeth whitening. Both tooth sensitivity and gum irritation are temporary and will subside within about a day following each treatment. If your teeth and/or gums are known to be sensitive or if you are considering peroxide based teeth whitening for the first time, the 22% whitening gel is recommended. The 22% whitening gel will whiten teeth as well as the 35% with a few more treatments but with less potential for discomfort.
For both the 22% and 35% whitening gel, it is advised on instructions-for-use cards provided that "Should tooth sensitivity persist, reduce treatment frequency and/or duration. If continued discomfort is apparent, discontinue use and consult your dentist." MGS recommends that first time users try a lower concentration first.
All whitening gels are intended for use by individuals with healthy teeth and gums. Gel should not be used if you have periodontal disease, decayed teeth or open mouth sores. A de-sensitizing gel > product link is available to reduce the transient sensitivity. MGS recommends the use of the sensitivity pen.