Comparative analysis of various temporary computer-aided design/computer-aided manufacturing polymethyl methacrylate crown materials based on color stability, flexural strength, and surface roughness: An in vitro study

Abstract

With recent advancements in digital dentistry, computer-aided design/computer-aided manufacturing (CAD/CAM) processed prostheses have been in very much use recently. This study aims to assess and compare the properties of these materials to better enable the practitioners to select the type of materials for use in a normal clinical practice. This research study was commenced after the approval by our Institutional Review Board (IHEC/SDC/PROSTHO/21/119). Twelve specimens of each group (group 1: CAD/CAM milled prostheses and group 2: three-dimensional (3D) printed prostheses using rapid prototyping) were prepared using the ISO standardization 10477:2004. The flexural strength of the samples that were prepared was tested using a universal testing machine and the values obtained were evaluated. Other samples (ISO standardized) were collected for evaluation of color changes postaging and surface roughness of both groups. Unpaired t-test to analyze flexural strength and surface roughness and Paired t-test was used to statistically analyze the values obtained for color stability. Group 1 showed significantly higher flexural strength and significantly better color stability when the samples were subjected to thermocycling. The mean strength obtained for 3D printed polymethyl methacrylate (PMMA) was 80.06MPa, whereas the mean flexural strength recorded for milled PMMA was 128.32 MPa. There was not much difference observed in the surface roughness of both groups. CAD/CAM milled specimens presented with better color stability and strength when compared to 3D printed specimens. Practitioners should be cautious while using three-dimensionally printed temporary prostheses in the posterior tooth region.

Keywords: Color stability; computer-aided design/computer-aided manufacturing; digital dentistry; flexural strength; milling; provisional prosthesis; surface roughness; three-dimensional printing.

Figure 1

Specimen preparation

Figure 2

Evaluation of surface roughness using stylus profilometer

Figure 3

3-point bend test for flexural strength done using UTM (mean flexural strength of 3D printed group: 80.06 ± 0.95 MPa, for milled group: 128.32 ± 0.35 MPa)

Figure 4

Evaluation of color stability using a spectrophotometer

Figure 5

Bar graph indicating the flexural strength of milled and printed PMMA (3D printed PMMA was 80.06 ± 0.95 MPa; milled PMMA was 128.32 ± 0.35 MPa). PMMA: Poly methyl methacrylate

Figure 6

Bar graph indicating the mean surface roughness of milled and printed PMMA (3D printed group: 0.005 ± 0.0007 μ; for milled group: 0.005 ± 0.0004 μ). PMMA: Poly methyl methacrylate

Figure 7

Bar graph depicting the color stability of both groups