Pre Digital Era
Taking a PVS impression provided physical retraction on the tissue enough to flow in between the margin and the free gingiva. This allowed for all prep styles to be implemented by dentists. Despite this benefit, PVS impressions resulted in a high likelihood of pulls/distortions and a high refabrication rate.
Digital scans benefit most from adequate tissue retraction and in the event of a poor scan identified chairside, minimal effort is required to re-scan for optimal results.
Double Cord Technique is Best!
Double cord is the best option for retraction due to the increased accessibility and improved displacement of tissue. Pack two knitted cords (soaked in a hemostatic material and at different diameters) and leave the larger cord in place for at least five minutes before pulling and scanning for optimal results.
Single Cord Technique is Acceptable.
Using a single cord is an adequate option as long as the margin is visible and the tissue has not collapsed prior to scanning - ensure the cord is soaked in hemostatic material and left in place for five minutes before pulling and scanning for optimal results.
Laser (Gingivectomy) Less Than Ideal, but Acceptable.
While there remains a barrier to entry based on cost, laser is more effective for retraction than the sole use of paste, but the risk of scarring and lack of mechanical traction makes this option less suitable for digital dentistry.
Paste is Not Suitable.
The use of paste is the farthest removed from any sense of mechanical retraction, and commonly introduces artifacts, leading to washed margins and suboptimal scans.