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. 2021 Mar 13;14(6):1401.
doi: 10.3390/ma14061401.

Influence of Sequential CAD/CAM Milling on the Fitting Accuracy of Titanium Three-Unit Fixed Dental Prostheses

Doo-Bin Song  1   2 , Man-So Han  2 , Si-Chul Kim  3 , Junyong Ahn  1 , Yong-Woon Im  4 , Hae-Hyoung Lee  1
Affiliations

Influence of Sequential CAD/CAM Milling on the Fitting Accuracy of Titanium Three-Unit Fixed Dental Prostheses

Doo-Bin Song et al. Materials (Basel). .

Abstract

This study investigated the fitting accuracy of titanium alloy fixed dental prostheses (FDP) after sequential CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) fabrication. A three-unit FDP model connecting mandibular second premolars and molars was prepared and scanned to fabricate titanium FDPs by CAD/CAM milling. A total of six FDPs were sequentially milled in one titanium alloy disk using a new set of burs every time (n = 4). The fitting accuracy of FDPs was mesiodistally evaluated by a silicone replica technique and the measurement was triplicated at four different locations: MO (marginal opening), MG (marginal gap), AG (axial gap), and OG (occlusal gap). Data were statistically analyzed using ANOVA and Tukey's HSD test. The fitting accuracy of PMMA (polymethyl methacrylate) FDPs milled using the worn or new bur were evaluated by the same procedure (n = 6). The mean dimensions of titanium FDP for all measuring positions, except for AG, were significantly increased from the third milling. However, no difference was noted between the first FDP and the second FDP milled with the same set of burs. Severe edge chippings were observed in all milling burs. Detrimental effects of the worn burs on the fitting accuracy were demonstrated in the CAD/CAM-milled PMMA FDP. The results recommend proper changing frequency of cutting burs to achieve the quality of fit and predictable outcomes for dental CAD/CAM prostheses.

Keywords: CAD/CAM; bur wear; fitting accuracy; fixed dental prosthesis; sequential milling.

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Conflict of interest statement

The authors declare that there are no conflict of interest in this study.

Figures

Figure 1
Figure 1
(A) Design of standard three-unit fixed dental prostheses (FDP), (B) designed FDP, and (C) sequentially milled Ti FDP on Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). The numbers indicate the milling sequence. (D) Seated on FDP die with light-body silicone.
Figure 2
Figure 2
Diagram for measurement locations of MO (marginal opening), MG (marginal gap), AG (axial gap), OG (occlusal gap), and silicone replica.
Figure 3
Figure 3
Box plot for marginal opening and gap dimensions of Ti-6Al-4V three-unit fixed dental prostheses (FDPs) according to the milling sequence. The same letters at each location indicate no statistical significance between the milling sequences at p < 0.05.
Figure 4
Figure 4
Difference in fitting accuracy of poly (methyl methacrylate) (PMMA) three-unit fixed dental prostheses (FDP) milled by as-received new bur and the worn burs used for milling of six titanium FDPs.
Figure 5
Figure 5
Edge chippings of milling burs with various diameters after milling of six three-unit FDPs. (A) 1.0 mm, (B) 2.0 mm, and (C) 3.0 mm.
Figure 6
Figure 6
Scanning electron microscopy (SEM) photographs of boundary areas (asterisk marks) remained between the inner and outer milling surface at the crown margins (red circled area) of the first-milled FDP (A) and the sixth-milled FDP (B). The white dashed line (A) indicates the margin line at MO area.
See this image and copyright information in PMC

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