An in vitro comparison of the marginal fit of provisional crowns using the virtual tooth preparation workflow against the traditional technique

Abstract

Aim: This study investigates the effectiveness of an innovative virtual tooth preparation workflow for the fabrication of dental crowns using cone-beam computed tomography (CBCT) and intraoral scanners (IOSs) with conventional workflow using extraoral/laboratory scanners.

Settings and design: This in vitro experimental study was conducted in the laboratory of a university in Chennai, India. The dental laboratory and research facilities at the institution were utilized for the fabrication of the temporary crowns and the data acquisition process.

Materials and methods: Institutional approval was obtained from the university. It was basically a comparison between the virtual prep technique using CBCT and IOS and the conventional digital technique using extra oral scanners (EOS) for temporary crown fabrication. The sample size was estimated using an effect size of 1.5004, assuming a normal distribution, a significance level of 0.05, and a power of 0.95 in G power software. Based on this calculation, an extracted second lower molar was used to fabricate 10 samples in each group. The samples were divided into three groups: the CBCT (Group 1), the IOS (Group 2), and laboratory scanner (Group 3 as control) groups. The vertical marginal gap of all the surfaces of the crown was evaluated using a scanning electron microscope.

Statistical analysis used: Data were analyzed using one-way ANOVA using the SPSS software version 26.0, IBM, Armonk, NY, USA.

Results: Acceptable marginal discrepancy values were obtained in all three groups. There was no significant difference in the marginal discrepancy recorded (P = 0.113).

Conclusion: Virtual tooth preparation using CBCT and IOSs can be used as an alternative to the conventional workflow for provisional crown and bridge fabrication.

Keywords: Cone-beam computed tomography; digital dentistry; intraoral scan; marginal fit; virtual tooth preparation.

Figure 1

Flowchart describing the methodology for fabricating the temporary PMMA crowns using three different scanning protocols. CBCT: Cone-beam computed tomography, DICOM: Digital Imaging and Communications in Medicine, STL: Standard tessellation language, D2P: DICOM to print, CAM: Computer-aided manufacturing, IMES: Integrated mechanics electronics software, SEM: Scanning electron microscope

Figure 2

Cone-beam computed tomography (CBCT) scanning protocol of crown fabrication (a: CBCT recorded in DICOM format, b: file converted to standard tessellation language [STL] file format, c: Crown designed on 3Shape dental manager using the virtual tooth preparation workflow, d: Final crown prosthesis STL file)

Figure 3

Intraoral scanning protocol of crown fabrication (a: Intraoral scanning using 3Shape Trios intraoral scanner, b: Standard tessellation language [STL] file format obtained, c: Crown designed on 3Shape dental manager using the virtual tooth preparation workflow, d: Final crown prosthesis STL file)

Figure 4

Conventional tooth preparation workflow (a: Tooth preparation done on the sample to accept polymethyl methacrylate (PMMA) crowns followed by. b: recording two stage putty impression. c: Tooth preparation scan to accept. d: PMMA crown fabrication)

Figure 5

Scanning electron microscope analysis (×250) of the marginal discrepancy of the (a) control and (b) cone-beam computed tomography and (c) intraoral scanner groups

Figure 6

Bar graph depicting the mean marginal discrepancy of all three groups recorded for each surface of the tooth was derived using a one-way ANOVA test (F = 2.218). CBCT: Cone-beam computed tomography, IOS: Intraoral scanners