In Vitro Comparative Study Between Full-Arch Conventional Implant Impressions and Full-Arch Digital Implant Impressions with Snap-on Scan Bodies
3D printed models
Prosthodontics and Prosthodontology
Statement of Problem: Digital impression techniques are widely used in everyday cases. There is sufficient evidence to support this technique in partially edentulous patients but the evidence supporting the use of intraoral scanners (IOS) in restorative digital workflows for edentulous patients is still limited. Purpose: The aim of the present in vitro study was to measure and compare the accuracy of full- arch conventional implant impressions with open and closed-trays, full-arch digital implant impressions with intraoral scanners (IOS), and three-dimensional (3D) printed casts from the full-arch digital implant impressions. Material and methods: Six implants were placed into a mandibular model. Snap-on scan bodies were inserted into the implants and scanned with a high-resolution reference scanner and exported in standard tessellation language (.STL) format (Group Control). Splinted open-tray impressions (Group 1, n=5) and closed-tray impressions (Group 2, n=5) were made and stone casts were fabricated. Digital impressions (Group 3, n=5) were made with an intra-oral scanner and the .STL files were exported to fabricate 3D printed casts. Snap-on scan bodies were inserted into analogs in Groups 1, 2, and 3 and scanned with the reference scanner. Using a 3D inspection software, impression techniques were compared to the control. Root mean square (RMS) values were calculated from the control and superimposed digitized casts from different impression techniques. Results: Group 3 had the lowest mean dimensional difference when superimposed with Group Control, then Groups 4, 1, and 2. Significant differences were found in RMS values between Group Control and digitized models fabricated from different techniques (P<0.05). Post Hoc (Tukey) test revealed that Group 3 (P<0.001) was significantly different from other groups while no significant difference was found between Groups 1, 2, and 4 (P>0.001). Conclusions: 3D printed models from full-arch digital impression of Snap-on scan bodies seem to be as accurate as stone models fabricated from full-arch conventional impression techniques. Closed-tray full-arch impression technique using dual-functioning Snap-on scan bodies seem to be as accurate as the splinted open-tray full-arch technique.