Surface Quality of 3D-Printed Models as a Function of Various Printing Parameters

Abstract

Although 3D-printing is common in dentistry, the technique does not produce the required quality for all target applications. Resin type, printing resolution, positioning, alignment, target structure, and the type and number of support structures may influence the surface roughness of printed objects, and this study investigates the effects of these variables. A stereolithographic data record was generated from a master model. Twelve printing processes were executed with a stereolithography Desktop 3D Printer, including models aligned across and parallel to the printer front as well as solid and hollow models. Three layer thicknesses were used, and in half of all processes, the models were inclined at 15°. For comparison, eight gypsum models and milled polyurethane models were manufactured. The mean roughness index of each model was determined with a perthometer. Surface roughness values were approximately 0.65 µm (master), 0.87-4.44 µm (printed), 2.32-2.57 µm (milled), 1.72-1.86 µm (cast plaster/alginate casting), and 0.98-1.03 µm (cast plaster/polyether casting). The layer height and type and number of support structures influenced the surface roughness of printed models (p ≤ 0.05), but positioning, structure, and alignment did not.

Keywords: 3D-printing; dental model; layer height; support structure; surface roughness.

Figure 1

Master model.

Figure 2

Model positioning (A: across the front; P: parallel to the front).

Figure 3

Printed model, with a layer thickness of 100 µm, angulated with a support structure.

Figure 4

Course of the traversing lengths and measurement directions.

Figure 5

Mean values of surface roughness Ra as a function of various printing parameters in comparison with the reference models and the master model; all dimensions are in µm. X, Y, Z: measurement directions (see Figure 4, values of the measurement directions X1/X2, Y1/Y2, and Z1/Z2 were summarized); parallel/across: models’ alignment to the printer’s front (see Figure 2).

Figure 6

Printing defect observed in all 0° samples at the same position on the build platform.

Figure 7

Printed models (from left: 0° and 25, 50, 100 µm; 15° and 25, 50, 100 µm). The distinct staircase-effects were found in models of lower resolution (100 µm, 3rd and 6th model from left). Models printed at 15° inclination at highest resolution showed best surfaces (25 µm, 4th from left).

Figure 8

Graphical representation of the relation between pull-off forces and surface roughness in overhang areas. Z1, Z2: measurement directions in the vertical dimension.