What precaution should be taken when placing bands to avoid overhangs?

When placing bands, ensuring proper band isolation is crucial to avoid overhangs. Proper isolation prevents saliva and moisture from contaminating the area being worked on, which can lead to inadequate bonding of the band to the tooth structure. When the band is not properly isolated, the cement may not set correctly, which can cause a gap or excess material that results in an overhang. Effective isolation allows the dental assistant to achieve a clean and precise application, ensuring that the band fits well against the tooth.

While the other options may be relevant in different contexts, they do not specifically address the key concern of preventing overhangs during band placement as directly as proper isolation does. Extra cement could lead to an unwanted buildup, double-checking the contours, while important, does not ensure the placement will be properly executed without the right isolation, and contouring the band is a subsequent step that does not address the immediate concern of moisture control during application.