By definition, the gum barrier is a protection for the client's gums. The 0.1% hydrogen peroxide gel is therefore very low in dosage. It is also used with a mouthpiece that allows the gel deposit to be targeted to the teeth. It is therefore not necessary to apply an additional gingival barrier.
Nevertheless, if you are confronted with clients who report that they have sensitive gums, the gum barrier can be a very suitable solution. This way, you will be performing a classic teeth whitening procedure with an additional protection that is a strong element of reassurance for your clients.