Subgingival Zone Detection via Reverse Subgingival Scan

An important issue with digital impression techniques is the difficulty in replicating the subgingival zone, particularly when abutments are prepared with a vertical finish line. We propose a novel procedure, the reverse subgingival scan (RSS), to depict the subgingival area via digital impression without a retraction cord or the distortion of the sulcus. The software workflow, beginning with a digital dental impression, was performed using Exocad^® (Align Technology) and Meshmixer^® (Autodesk). The approach is based on the direct alignment of the surface of abutments, which is used as a reference point. The efficacy of the RSS approach was confirmed via fit tests, radiographic control assessments, and evaluations of the rate of tissue compression of the final prosthetic restoration, so long as the provisional had a perfect fit. RSS yields information on the transversal dimension and depth of the gingival sulcus. The procedure depends on the quality and characteristics of the provisional restoration, and is suitable only for cases in which the finish line of the final crown is at the same level or more coronal than that of the provisional.