Accuracy of intraoral scans of the edentulous maxilla - an in vitro study

Abstract

Objective: Investigation of the accuracy of various digitalization methods and the accuracy of digitalization of different regions of the edentulous maxilla.

Material and method: A PEEK edentulous maxilla with four spherical reference geometries served as the testing model. A reference dataset (REF) was generated using a highly accurate 3D measuring instrument. The testing model was digitized as follows (n = 25/group). Direct digitalization (DD) with intraoral scanners (IOS): 1) Cerec AC Primescan (PRI), 2) Trios 4 Move (TR4), 3) Trios 3 Wireless (TR3), 4) Indirect digitalization of PVS impression with laboratory scanner 3Shape D810 (D8I). Three-dimensional deviations between REF and TEST were evaluated (GOM Inspect) in different areas of the model: 1) Complete Surface, 2) Alveolar Ridge, 3) Vestibular Ridge, 4) Palate, 5) Posterior Seal, 6) Border. Significant differences were analyzed with the Games-Howell test for trueness (p < 0.05) and multiple comparisons Levene's test for precision (for IOS: p < 0.008, for area: p < 0.003).

Results: Group D8I revealed the best trueness for Complete Surface (7.95 µm), Palate (9.11 µm), and Border (20.22 µm). Alveolar Ridge showed for PRI (16.45 µm) and TR4 (8.96 µm) the highest trueness. Groups TR4 and PRI resulted in significantly higher precision for Alveolar Ridge. Groups TR4 and D8I demonstrated the highest precision for Palate. Complete Surface and Alveolar Ridge showed for all digitalization methods significantly higher precision.

Conclusions: Indirect digitalization of impressions remains the most accurate approach for capturing edentulous jaws, whereas IOS deliver datasets with clinically acceptable accuracy. Peripheral regions characterized by limited accessibility and smooth surface morphology tend to demonstrate increased deviations in the resulting digital datasets.

Clinical relevance: Indirect digitalization of the impression still appears to be the most appropriate technique to access the clinical workflow for full dentures due to the superior digitalization trueness and inclusion of functional movements. Direct and indirect digitalization show nearly equal values for precision.

Keywords: Accuracy; Coordinate-based data analysis; Digital dentistry; Digital full-arch impression; Edentulous; Intraoral scanner; Precision; Trueness.

Fig. 1

Testing model milled from PEEK

Fig. 2

Reference dataset

Fig. 3

PVS impression

Fig. 4

Alignment of test datasets with REF. a. REF. b. Best fit alignment on selected areas. c. Aligned test and REF datasets

Fig. 5

Investigated areas: a. Complete Surface. b. Vestibular Ridge. c. Alveolar Ridge. d. Palate. e. Posterior Seal. f. Border

Fig. 6

Cross section of measured distances between points on REF and test datasets in the metrological software

Fig. 7

Boxplots for digitalization methods (Cerec AC Primescan (PRI), Trios 4 Move (TR4), Trios 3 Wireless (TR3), Indirect digitalization of PVS impression with laboratory scanner 3Shape D810 (D8I)) and digitalization areas (Complete Surface, Alveolar Ridge, Vestibular Ridge, Palate, Posterior Seal, Border)