Impact of digital manufacturing methods on the accuracy of ceramic crowns

The purpose of the present study was to assess the accuracy of full-coverage crowns produced by two manufacturing methods: additive 3D printing and subtractive milling utilizing three different predefined cement spaces.

Nine groups were allocated based on the manufacturing method and the predefined cement space: printed wax with a 20-µm cement space (PW1); printed wax with a 50-µm cement space (PW2); printed wax with a 100-µm cement space (PW3); milled wax with a 20-µm cement space (MW1); milled wax with a 50-µm cement space (MW2); milled wax with a 100-µm cement space (MW3); milled zirconia coping with a 20-µm cement space (MZ1); milled zirconia coping with a 50-µm cement space (MZ2); milled zirconia coping with a 100-µm cement space (MZ3). All fabricated specimens were scanned using a Medit Identica Blue 3D scanner and saved as standard tessellation language (STL) files. A triple scan method was performed using Materialise 3-matic software to assess accuracy. The discrepancy values were recorded in micrometers (µm), and the analysis was conducted using one-way analysis of variance (ANOVA).

The wax printing method, with a cement gap design of 100 μm, demonstrated a significant improvement in accuracy compared with the other methods (P 0.01). In contrast, the zirconia milling method exhibited significantly lower accuracy relative to the other techniques (P 0.01). Moreover, different cement spaces resulted in various accuracy levels, but the only statistically significant difference was observed for the 100-µm cement space in the printed wax group (PW3).

The additive 3D-printing method exhibited greater accuracy than the subtractive milling method. Furthermore, altering the cement gap was found to impact the accuracy of both techniques, albeit without statistical significance.