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UBC Theses and Dissertations

Multiple implants impression accuracy of edentulous jaw : digital and conventional implant impression comparative study AlTuwaijri, Sahr


Statement of problem: The use of digital impressions for implants are limited to single and short span bridges due to the few available studies supporting their usage in more complex cases. Therefore, its essential to evaluate their accuracy in full arch cases to benefit from their great advantages. Purpose: Evaluate and compare the accuracy of digital and conventional impressions for multiple straight and angulated implants of full arch implant supported fixed prosthesis. Also, assess the effect of implant angulation of 45° and increased length on the accuracy of both methods. Materials and methods: A stereolithographic (SLA) model of edentulous mandibular cast was fabricated and used to produce the master stone cast with four Nobel CC RC implants placed at tooth positions 3.4, 3.2, 4.2 and 4.4. Implants at #32 and 42 were perpendicular to the occlusal plane and parallel to each other while implants at #34 and 44 were distally angulated with 45°. Three impression methods were made from the master stone cast. Digital impressions were made with Trios (3Shape, Copenhagen, Denmark) intraoral scanner (IOS) (n=10). Conventional splinted open-tray implant–level impressions were made with Polyvinyl (PVS) (n=10) and Polyether (PE) (n=10). All stone casts were digitized using a 3shape D800 lab scanner to obtain STL (standard tessellation language) files, which then were imported into Rhino5 3D software. Six linear measurements were obtained for each cast to evaluate their discrepancies from the master cast. Absolute values of the linear deviation of each line among the three groups were compared using Kruskal-Wallis test and Dunn's post hoc test. Results: Significant difference (P< 0.05) were found between Trios and PVS and between PE and PVS for the distance between Implant #42 and 44. Also, for the distance between implant #32 and 44 between PE and Trios, and between PE and PVS. No significant difference was found for the other lines. Conclusion: The PE impression technique was more accurate than the others and all methods were considered clinically acceptable. The 45° degree of angulation and the increased length had affected the accuracy of PVS and Trios groups.

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