If the rubber dam is lying on the tooth surface it may allow leakage of saliva, a problem particularly when the dam has been applied during adhesive restorative procedures, but also with endodontics. The margin should be everted into the gingival crevice as shown in Figure 14.
The operator stretches the rubber away from the tooth whilst the assistant directs a stream of cold air from the triple syringe onto the mucosa. With the use of a flat plastic instrument the margin of the rubber dam may be tucked into the gingival crevice, providing a tight seal.
Alternatively, some operators apply floss ligatures, as shown in Figure 15, using a flat plastic to push the floss above the cingulum, and tying a knot securely on the labial aspect of the tooth.