Marginal and vertical discrepancies of three unit metal posterior fixed dental prosthesis manufactured by other manufacturing methods

Background

In the field of dental prosthetics, advances in digital dentistry have resulted in not only new impression methods, but also new fabrication methods. Traditionally, metal prostheses were produced by casting methods, but in recent times, computer-aided design and computer-aided production methods are being proposed. But comparisons of the accuracy of prostheses made with different processing techniques are lacking.

Aim/Hypothesis

The aim of this in vitro study is to compare the marginal and internal fit of milling metal and 3D printing metal 3 unit posterior fixed dental prosthesis

Material and Methods

Teeth preparation for # 35 = 37 3 unit posterior fixed dental prosthesis was performed on typodont. The model was scanned 10 times with the intraoral scanner. Teeth were prepared according to the guidelines for traditional metal ceramic crowns. A circumferential deep chamfer margin was created, and occlusal reduction of 1.5 to 2 mm was performed. Each ten specimens were fabricated with milling Co-Cr alloy, 3D printing Co-Cr alloy with scan data. The cement thickness was set as 30 micrometer, starting from 1.0 mm occlusal to the margin. The marginal and internal gaps of the copings were measured using a replica technique with a light-body silicone impression material. The replica specimens were sectioned buccopalatally and mesiodistally and then examined using a microscope at 200◊ magnification. Sixteen reference points were used on each specimen. The data were statistically analyzed with independent t test (P > .05)

Results

The marginal gap of the milled prostheses was 35.85 micrometers, and 3D printed prostheses was 43.67 micrometers in the premolar. The means at the axial wall region were 73.61 micrometers for the milled group, 80.06 micrometers for the 3D printed group. Milled prostheses showed a better fit at the premolar. The marginal gap of the milled prostheses was 35.91 micrometers, and 3D printed prostheses was 39.15 micrometers in the molar. The means at the axial wall region were 65.26 micrometers for the milled group, 76.01 micrometers for the 3D printed group. The means at the occlusal wall region were 90.72 micrometers for the milled group, 83.90 micrometers for the 3D printed group. In the molar, the milling method showed a better fit, but on the occlusal region, 3-printing was better.

Conclusion and Clinical Implications

Overall, milling method showed significantly small gaps, but both methods showed clinically satisfactory fitness. It is expected that the digital manufacturing method will be useful for metal processing.