Influence of printing angulation on the surface roughness of additive manufactured clear silicone indices: An in vitro study

Statement of problem. Vat-polymerization additive manufacturing (AM) technologies can be used to fabricate clear silicone indices for diagnostic trial restorations, interim restorations, and direct composite resin restorations. Different support parameters, including print orientation of the virtual design of the silicone index, need to be determined when a dental device is fabricated with AM. However, the optimal printing angulation for minimal surface texture remains unclear. Purpose. The purpose of this in vitro study was to measure the surface roughness of the AM clear silicone indices manufactured by using a vat-polymerization 3D printer with different print orientations. Material and methods. A virtual design of a facial silicone index was obtained, and the standard tessellation language file was exported and used to manufacture all the specimens using a vat-polymerization 3D printer. All the specimens were placed on the build platform with the same parameters, except for the print orientation which was selected as the only manufacturing variable. Therefore, the 5 different groups were 0, 25, 45, 75, and 90 degrees. To minimize variation in the procedure, all the specimens (N=50) were manufactured at the same time in the selected printer at a constant room temperature of 23 degrees C. The printer had been previously calibrated following the manufacturer's recommendations. Surface roughness was measured in the intaglio of the left central maxillary incisor using an optical profilometer with a magnification of x20 and an array size of 640x480. Three measurements per specimen were recorded. The Shapiro-Wilk test revealed that the data were normally distributed, and the data were analyzed by using 1-way ANOVA, followed by the post hoc Sidak test (alpha=.05). Results. The 0-degree angulation printing group reported the least mean +/- standard deviation surface roughness (0.9 +/- 0.3 mu m), followed by the 90-degree group (3.0 +/- 0.6 mu m), the 75-degree group (12.4 +/- 1.0 mu m), the 25-degree group (13.1 +/- 0.9 mu m), and the 45-degree group (13.5 +/- 1.0 mu m). However, no statistically significant difference was found in the surface roughness between the 25-degree and 45-degree print orientation groups (P=.296). Conclusions. Print orientation significantly influenced the surface roughness measured on the intaglio of the facial AM silicone indices tested.

Automated summary

This in vitro study aimed to measure the surface roughness of AM clear silicone indices manufactured using a vat-polymerization 3D printer with different print orientations. The results indicated that print orientation significantly influenced the surface roughness of the facial AM silicone indices tested.