Browsing by Subject "milling"

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    The effects of manufacturing technologies on the surface accuracy of CAD-CAM occlusal splints
    (Wiley, 2022) Orgev, Ahmet; Levon, John A.; Chu, Tien-Min G.; Morton, Dean; Lin, Wei-Shao; Prosthodontics, School of Dentistry
    Purpose To investigate the effects of the manufacturing technologies on the surface (cameo and intaglio) accuracy (trueness and precision) of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal splints. Materials and methods The digital design of the master occlusal splint was designed in a CAD software program. Six groups (n = 10) were tested in this study, including Group 1 – Milling (Wax), Group 2 – Heat-polymerizing, Group 3 – Milling (M series), Group 4 – Milling (DWX-51/52D), Group 5 – 3D-printing (Cares P30), and Group 6 – 3D-printing (M2). The study samples were placed in a scanning jig fabricated from putty silicone and Type III dental stone. The study samples were then scanned with a laboratory scanner at the intaglio and cameo surfaces, and the scanned files were exported in standard tessellation language (STL) file format. The master occlusal splint STL file, was used as a reference to compare with all scanned samples at the intaglio and cameo surfaces in a surface matching software program. Root mean square (RMS, measured in mm, absolute value) values were calculated by the software for accuracy comparisons. Group means were used as the representation of trueness, and the standard deviation for each group was calculated as a measure of precision. Color maps were recorded to visualize the areas of deviation between study samples and the master occlusal splint file. The data were normalized and transformed to rank scores, and one-way ANOVA was used to test for the differences between the groups. Pairwise comparisons were made between different groups. Fishers least square differences were used to account for the family-wise error rate. A 5% significance level was used for all the tests. Results The null hypotheses were rejected. The manufacturing technologies significantly affected the trueness of occlusal splints at both intaglio and cameo surfaces (p < 0.001). At the cameo surfaces, Group 1 – Milling (Wax) (0.03 ± 0.02 mm), Group 3 – Milling (M series) (0.04 ± 0.01 mm), and Group 4 – Milling (DWX-51/52D) (0.04 ± 0.01 mm) had the smallest mean RMS values and highest trueness. Group 3 had the smallest standard deviation and highest precision among all groups (p < 0.001, except p = 0.005 when compared with Group 2). Group 5 had the largest standard deviation and lowest precision among all groups (p < 0.001). At the intaglio surfaces, Group 1 – Milling (Wax) (0.06 ± 0.01 mm) had the smallest RMS values and highest trueness among all groups (p < 0.001), and Group 2 – Heat-polymerizing (0.20 ± 0.03 mm) and Group 5 – 3D-printing (Cares P30) (0.15 ± 0.05 mm) had significantly larger mean RMS and standard deviation values than all other groups (p < 0.001), with lowest trueness and precision. In the color maps, Group 2 – Heat-polymerizing and Group 5 – 3D-printing (Cares P30) showed the most discrepancies with yellow and red (positive discrepancies) in most areas, and Group 1 – Milling (Wax) showed the best and most uniform surface matching with the most area in green. Conclusion The manufacturing technologies significantly affected the trueness and precision of occlusal splints at both intaglio and cameo surfaces. The 5-axis milling units and industrial-level CLIP 3D-printer could be considered to achieve surface accuracy of occlusal splints.
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    Translucency parameter and color masking ability of CAD-CAM denture base materials against metal substrates
    (Wiley, 2023-04) Wang, Yun-Ju; Chu, Tien-Min G.; Lin, Wei-Shao; Prosthodontics, School of Dentistry
    Purpose To investigate the translucency parameters of traditional, milled, and 3D-printed denture base materials at 3 different thicknesses and the color masking ability of each material against a metallic background between different thicknesses. Material and methods A traditional heat-polymerizing polymethylmethacrylate (PMMA) (H-Lucitone) material was used as the control group. Two milled pre-polymerized resin blocks (M-Lucitone and IvoBase) and five 3D-printed denture base materials (P-Lucitone, Dentca LP, Dentca OP, Formlabs, and Kulzer) were used as experimental groups. A total of 240 samples, (n = 30, per material) were fabricated to a final specimen dimension of 12×12 mm and in thicknesses of 1.0, 2.0, and 3.0 mm (n = 10 per thickness/material) according to the manufacturers’ recommendations. The color coordinates (L*, a*, b*) in CIELab color space for all specimens placed against a white, black, and metallic background were measured with a spectrophotometer. The translucency parameters (TP00) at each thickness and the color differences between 1 mm and 2 mm (dE00M1-2) and between 2 mm and 3 mm (dE00M2-3) against the metallic background were calculated with the CIEDE2000 color matrix. Comparisons between the groups for differences in TP00 were made using One-way ANOVA separately for each thickness. Comparisons of groups and materials for differences in dE00M1-2 and dE00M2-3 were made using Two-way ANOVA and Fisher's Protected Least Significant Differences (α = 0.05). Results The TP00 decreased with increasing thickness in all 8 material groups. All 3D-printed materials, except P-Lucitone, had higher TP00 than milled pre-polymerized resin materials (M-Lucitone and IvoBase), and traditional heat-polymerizing PMMA (H-Lucitone) material (P<.001) at all thicknesses. In the 1 mm and 2 mm thickness, heat-polymerizing acrylic resin (H-Lucitone) had the lowest TP00, and in the 3 mm thickness, milled acrylic resin (M-Lucitone and IVOBase) had had lowest TP00 (p < 0.001). All material groups had significantly lower values of dE00M2-3 than dE00M1-2 (p < 0.001). The color differences dE00M2-3 were significantly lower in H-Lucitone, M-Lucitone, P-Lucitone, and IvoBase groups than in other materials, while the color difference of dE00M1-2 was significantly lower in H-Lucitone, P-Lucitone and Dentca LP than other materials (p < 0.001). Conclusions The results from this study provide clinicians and dental technicians with information regarding the selection of denture base materials to achieve desired color masking outcomes, according to available prosthetic space. Thicker prostheses significantly improved the color masking abilities of denture acrylic resins against a metallic background. In a thickness of 1 and 2 mm, the heat-polymerizing acrylic resin had a lower translucency parameter and better color masking ability. When the prosthesis thickness reached 3 mm, the milled acrylic resin had a lower translucency parameter and better color masking ability. When compared to the heat-polymerizing resin and milled acrylic resin materials, except for one 3D-printing resin (P-Lucitone), the color masking abilities of the remaining 3D-printing resin materials were low, regardless of prosthesis thickness.