Comparative In Vitro Study on the Accuracy of Stone Casts from Conventional Implant Impressions Versus Printed Casts Generated from Digital Implant Impressions
Abstract: Aim & Hypothesis: In order to fabricate passively fitting implant prosthesis, the master cast utilized for prosthesis fabrication must be accurate. The aim of this in vitro study was to compare the three-dimensional (3-D) accuracy of printed implant casts generated from digital impressions with two intraoral scanners (CEREC Omnicam and 3M True Definition) vs conventional stone casts fabr... read moreicated by splinted open tray technique in a partially edentulous scenario. The hypothesis was that printed casts from digital impressions would be more accurate than stone casts from conventional impressions. Materials & Methods: A polymethylmethacrylate partially edentulous mandibular cast was fabricated using two internal connection tissue-level implants (Replace Select RP, Nobel Biocare). The two implants were not parallel to each other; one implant was parallel to the long axis of teeth in the arch while the other was positioned in 30 degrees angle. This cast was duplicated with polyether impression material in splinted open tray technique to produce a master cast that would serve as control. Digital impressions (n=10) were taken after connecting scan bodies with two intraoral scanners (CEREC Omnicam and 3M True Definition). Standard tessellation language (STL) datasets from the groups were used to print casts and implant analogs were retrofitted into the casts (Vareso, BEGO). The stone casts of the conventional impression group (n=10) were produced with the splinted open tray impression technique. Master cast, conventional stone casts and printed casts were digitized with an extraoral high resolution reference scanner (Activity 880scanner, Smart Optics, Bochum, Germany). STL datasets from the three groups were superimposed with the STL dataset of the master cast in inspection software (Geomagic control 2015) to calculate the 3D deviation as Root Mean Square error. Results: The conventional cast group had the lowest mean value (53.49 ± 9.47μm), followed by the Omnicam cast group as the second lowest mean value (108.09 ± 9.59μm). The True Definition cast group had the highest mean value (120.39 ± 5.91μm). The Shapiro-Wilk test showed no evidence of non-normality (p > 0.05 for each group) and the Levene's test showed no evidence of heterogeneity of variance (p = 0.518). The one-way ANOVA demonstrated a statistically significant difference (p < 0.001). Tukey's HSD showed statistically significant differences between all groups: for the comparison of True Definition and Omnicam, the p-value was 0.009, and the p-values of the other post-hoc tests were < 0.001. Conclusion: Within the limitations of this in vitro study, printed casts generated from digital impressions with 2 IOS systems have inferior accuracy to conventional stone casts fabricated from splinted open tray impressions. The printed casts from Omnicam had better accuracy when compared to printed casts from True Definition.
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Posthodontics.
Advisor: Panos Papaspyridakos.
Committee: Hans Peter Weber, Matthew Finkelman, Khaled El Rafie, and Yukio Kudara.
Keyword: Dentistry.read less