Which of the following best defines mechanical gingival retraction?

Mechanical gingival retraction is best defined as using a retraction cord. This method involves the placement of a cord in the sulcus around a tooth to displace the gingival tissue temporarily. This retraction allows for better visibility and access to the tooth structure, which is essential during dental procedures such as crown preparations and impressions. The cord helps to create a more accurate impression by minimizing the interference of the gingiva with the restoration process.

While other methods may involve materials or techniques used in dentistry, they do not specifically focus on the mechanical aspect of retracting the gingiva. For instance, using adhesive materials generally pertains to the bonding processes, employing topical anesthetics is related to pain management, and utilizing physical barriers could refer to a broader range of protective measures but does not specifically denote the targeted action of retraction provided by a cord. Therefore, the specificity and effectiveness of using a retraction cord in creating space around the tooth define it as the best choice for mechanical gingival retraction.