All ETDs from UAB

Advisory Committee Chair

Daniel A Givan

Advisory Committee Members

James C Broome

Keith Kinderknecht

Nathaniel Lawson

Perng-Ru Liu

Document Type


Date of Award


Degree Name by School

Master of Science in Dentistry (MScD) School of Dentistry


Purpose: To determine the precision and accuracy of the True Definition Scanner (3M) (TDS) to capture margins at different gingival heights. Materials and Methods: A typodont with soft gingiva and removable indexed Ivorine® teeth was used. Tooth #19 was prepared to fit an all-ceramic crown with a chamfer margin. Spacers placed beneath the prepared tooth elevated #19 in the typodont and controlled the tooth margin height relative to the gingival margin. The TDS was used as an intraoral scanner. A total of 50 scans were made with 5 groups of 10 scans each. In Group 1 (control) the prepared tooth margin was 1 mm supra- gingival, while in Group 2 the margin equi-gingival. In groups 3 through 5, the margin position was respectively 1, 2, or 3 mm infra-gingival. optical scans were generated following manufacturer’s recommended procedures. The STL files were processed using MeshLab software computer-aided analysis to trim to the tooth #19 margins producing a new output file. The new STL processed and surface area (SA) was measured using Netfabb software. All post-processing was performed by the same operator. Results: The measured SA of the scan groups was evaluated with one-way ANOVA and Tukey’s post-hoc test (p ≤ 0.05) and reveals a statistically significant difference between the groups. Post-hoc testing revealed no statistical difference between iii control group and equi-gingival group but did reveal statistical differences between each of the infra-gingival groups. Conclusion: Optical impressions using the TDS was determined to be reliable in producing precise impressions scans with supra-gingival and equi-gingival margins. However, as the position of the margin was located more infra-gingival, the scans become incomplete and result in loss of accuracy and precision compared to the control.

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