European Journal of Prosthodontics and Restorative Dentistry

Trueness and Precision Achieved With Conventional and Digital Implant Impressions: A Comparative Investigation of Stone Versus 3-D Printed Master Casts

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Cover Date

September 2021

Print ISSN

0965-7452

Electronic ISSN

2396-8893

Vol

29

Issue

3

Abstract

Objective: To analyze implant casts obtained from intraoral optical scanning and conventional impressions. Materials and Methods: Ten optical scans (test) and ten conventional polyether impressions (control) were obtained from a two-implant reference model. Ten casts each were manufactured additively or from stone. All casts were digitized and virtually superimposed to the digital reference (trueness) applying a best-fit algorithm, and secondary analysis for intra-group comparisons (precision). The signed nearest neighbor distance of each surface point (FDI:24/26) was computed and deviations of the three-dimensional vectors (X,Y,Z) analyzed. The groups were compared with the Wilcoxon’s rank sum test. Results: The printed casts had mean deviations of 106.0μm and
the stone casts 187.9μm compared to the reference. Controls had significantly higher deviations and dispersion (p<0.001). The printed casts showed mean intra-group deviations of 149.8μm and the stone casts 181.2μm without significant differences (p=0.162). There was no statistically significant difference in any of the vector analyses (X:p=0.105, Y:p=0.089, Z:p=0.123). Conclusion: Optical scanning seems to be an alternative to conventional impressions in terms of trueness and precision of implant master casts, simulating the scenario of a three-unit implant-supported fixed dental prosthesis. Digitally manufactured master casts might serve as reliable reference for the final restorations.
Keywords
Rapid Prototyping
Digital Dentistry
Intra-Oral Scan (IOS)
Implant Master Casts