The primary benefit of using rubber dam isolation during dental restorative treatments is improved moisture control. Maintaining a dry operative field is crucial for the adhesion and longevity of restorative materials such as composites. The rubber dam effectively prevents saliva, blood, and other fluids from contaminating the treatment area, ensuring optimal bonding conditions. Additionally, it aids in reducing bacterial contamination and improves overall treatment quality. While other benefits exist, control of moisture is the key clinical advantage that justifies rubber dam use in restorative procedures.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition.