What can be used to limit the exposure to the etchant?

The correct choice for limiting exposure to the etchant in the context of dental procedures is a rubber dam. A rubber dam is a sheet of rubber or latex that is stretched over the area of the mouth being treated, isolating the teeth and providing a barrier. This not only helps to keep the working area dry and free from saliva but also significantly reduces the risk of etchant exposure to soft tissues, such as gums and cheeks.

Using a rubber dam allows for a controlled application of etching materials, making it easier to apply them selectively to the tooth surface without accidentally affecting surrounding areas. This added layer of protection minimizes the potential for pain or irritation that could arise from contact with the etchant.

In contrast, while cotton rolls can absorb saliva and keep the area dry, they do not provide a complete barrier like a rubber dam does. Matrix bands are used to aid in the restoration process and do not serve to isolate the teeth from etchant exposure. Dental floss is typically used for cleaning between teeth and would not serve a role in limiting exposure to etchants at all. Thus, the rubber dam emerges as the most effective choice for protecting soft tissues from etchant exposure during dental procedures.