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Beom-Young Yu1, 2
, Keunbada Son1, 2, Kyu-Bok Lee2, 3
, Keunbada Son1, 2, Kyu-Bok Lee2, 3
Abstract
Purpose
The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner.
Materials and methods
A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (α=.05).
Results
The RMS mean abutment for single full crown preparation was 10.93 µm and the RMS average abutment for 3 unit bridge preparation was 6.9 µm. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged 9.83 µm, −6.79 µm and 3-units bridge abutment 6.22 µm, −3.3 µm, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001).
Conclusion
Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.
Figures and Tables
Fig. 2
Working model. (A) solid cast for single all-ceramic crown, (B) solid cast for 3-units fixed dental prosthesis.
Fig. 3
Working model with removable dies. (A) stone definitive removable die-sectioned cast for single all-ceramic crown, (B) stone definitive removable die-sectioned cast for 3-units fixed dental prosthesis.
Fig. 4
Scanning procedure using the model scanner. (A, B, C) Single model scan procedure, (D, E, F) 3-unit bridge model scan procedure, (A, D) Scanning the abutment, (B, E) Transforming to virtual model, (C, F) Superposition of CRM and abutment scan data.
Fig. 5
Color difference maps obtained from comparison between CRM and CTM (abutment for single all-ceramic crown).
Fig. 6
Color difference maps obtained from comparison between CRM and CTM (abutment for 3-units fixed dental prosthesis).
Fig. 7
Comparison of mean 3-dimensional analysis (root mean square avg. value) according to abutment type. Asterisk indicates significant difference by Mann-Whitney U-test at α = .05.
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