J Adv Prosthodont.  2014 Dec;6(6):468-473. 10.4047/jap.2014.6.6.468.

Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision

• Jeon JH
• Kim HY
• Kim JH
• Kim WC

• KMID: 2284720
• DOI: http://doi.org/10.4047/jap.2014.6.6.468

Abstract

PURPOSE
This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types.
MATERIALS AND METHODS
To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10degrees-20degrees and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (alpha=.05).
RESULTS
Precision discrepancies for the canine, premolar, and molar were 3.7 microm, 3.2 microm, and 7.3 microm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 microm, 11.2 microm, and 21.8 microm, respectively, indicating the poorest trueness for the molar (P=.007).
CONCLUSION
In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall.

Keyword

White light scanner; Accuracy; Precision and trueness; Impression scanning; 3D shape data; Point cloud

MeSH Terms

Bicuspid
Crowns
Molar
Tooth*

Figure

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  Fig. 1 Precision evaluation for the canine: Ten color-difference maps (A-J) of scans of the canine impression showing fit alignment of digital impression data compared among each other (C_pre1 through C_pre5). Trueness evaluation for the canine: Five color-difference maps (K-O) of scans of the canine impression showing fit alignment of digital impression data compared with the reference model data (C_tru1 to C_tru5). Green represents the exact fit, yellow to red represents a positive discrepancy, and turquoise to blue represents a negative discrepancy.

• 

  Fig. 2 Precision evaluation for the first premolar: Ten color-difference maps (A-J) of scans of the first premolar impression showing fit alignment of digital impression data compared among each other (P_pre1 through P_pre5). Trueness evaluation for the first premolar: Five color-difference maps (K-O) of scans of the first premolar impression showing fit alignment of digital impression data compared with the reference model (P_tru1 to P_tru5). Green represents the exact fit, yellow to red represents a positive discrepancy, and turquoise to blue represents a negative discrepancy.

• 

  Fig. 3 Precision evaluation for the first molar: Ten color-difference maps (A-J) of scans of the first molar impression showing fit alignment of digital impression data compared among each other (M_pre1 through M_pre5). Trueness evaluation for the first molar: Five color-difference maps (K-O) of scans of the first molar impression showing fit alignment of digital impression data compared with the reference model (M_tru1 to M_tru5). Green represents the exact fit, yellow or red represents a positive discrepancy, and turquoise to blue represents a negative discrepancy.

• 

  Fig. 4 Boxplot of discrepancies (precision and trueness) for the digitized impressions of the three types of abutment teeth obtained using a white light scanner: Precision (n=10 per type), trueness (n=5 per type).

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