Even the highest-class composite material will not do its job if placed in a moist environment. Saliva, water vapour from breathing, gingival blood – each of these acts at the microscopic level, compromising the bond between material and tooth.
The rubber dam – a latex or silicone sheet isolating the working field – eliminates this problem entirely. A clinical study by Falacho et al. (Journal of Esthetic and Restorative Dentistry, 2023) showed that rubber dam isolation significantly increases the bond strength of adhesives to enamel – and that without proper isolation, adhesive properties are objectively reduced.
It is not a convenience. It is a condition of properly performed work.