Final answer:
The most common method to obtain gingival retraction in dentistry is mechanical cord packing, which involves placing a thin cord around the tooth to push the gum tissue away.
Step-by-step explanation:
Gingival retraction, also known as gum retraction, is a procedure used in dentistry to expose more of the tooth's surface, particularly when taking impressions for crowns or other dental restorations. The most common method to obtain gingival retraction is mechanical cord packing. This involves placing a thin cord made of either cotton or non-impregnated retraction material around the tooth, which pushes the gum tissue away and creates space for the impression material. This method is preferred over the other options listed, as it is non-invasive and can be done relatively quickly.