Effects of support-structure design and postpolymerization protocols on dimensional changes in three-dimensionally...

Additive manufacturing technologies have become popular for the fabrication of complete dentures; however, the effects of different support-structure designs and postpolymerization protocols on denture accuracy remain unknown.

The purpose of this in vitro study was to evaluate the effects of different support-structure designs and postpolymerization protocols on the accuracy of 3-dimensionally (3D) printed complete dentures.

Simulated complete maxillary complete dentures were 3D printed using 2 support-structure designs: conventional and tree-like. Both types of complete dentures were maintained at different temperatures (40 °C, 60 °C, and 80 °C) for 15 and 30 minutes after polymerization. All specimens were optically scanned in the same orientation using a light scanner with an accuracy of 10 µm and repeatability of 4 µm. The acquired data for the intaglio surfaces of all complete dentures were exported into a 3D analysis software program. Scan data (n=8) were superimposed on the standard tessellation language (STL) reference file to evaluate trueness. In addition, scan data (n=28) were superimposed onto a combination of STL files for each protocol by using the combination formula (₈C₂=28) to evaluate precision. Root mean square error (RMSE) values were used to analyze dimensional changes in the denture base during the postpolymerization process. Two-way analysis of variance (ANOVA) with interaction was used to analyze the accumulated data, and the Tukey post hoc test was used for multiple comparisons (α=.05).

Overall, RMSE values for both trueness and precision were lower with the tree-like support structure than with the conventional support structure, and precision was significantly different between the groups (F=24.482, P<.001). Moreover, significant differences according to the postpolymerization protocols were observed in both trueness (F=15.104, P<.001) and precision (F=13.244, P<.001). The lowest RMSE values for both trueness and precision were observed in the 30-minute, 60-°C group. Although the support-structure design and postpolymerization protocols did not affect trueness, they significantly affected precision (F=2.362, P=.040).

The tree-like support structure improved the dimensional accuracy of the intaglio surface when the complete denture was maintained at 60 °C for 30 minutes after polymerization. The findings suggest that the relationship between the support-structure design and postpolymerization protocol influences the accuracy of 3D printed complete dentures.