Performance of stereolithography and milling in fabricating monolithic zirconia crowns with different finish line designs.

Subtractive manufacturing has become the dominant method in fabricating zirconia dental restorations while additive manufacturing is emerging as a potential alternative. The aim of this in vitro study was to investigate the performance of stereolithography (SLA) and milling in fabricating monolithic zirconia crowns with different finish line designs. Full-contour crowns with three finish lines (chamfer, rounded shoulder, knife-edge) were designed and fabricated by SLA and milling. Fabrication accuracy was accessed by 3D deviation analysis and margin quality was characterized under microscopes. The obtained root mean square value was significantly influenced by finish line design (P < 0.05) but not by fabrication method (P＞0.05). However, the color-difference map showed crowns fabricated by SLA and milling had different error distribution in external surfaces. SLA-printed crowns exhibited margins of rounded line angle and without small flaws, although large chippings were found in knife-edged crowns. In milling group, crowns showed margins of sharp line angle and with separate chippings. More and larger margin chippings were found in knife-edged crowns by milling. The results indicate that SLA and milling can fabricate monolithic zirconia crowns of comparable accuracy and knife-edged crowns are prone to large margin chippings by either of the two manufacturing methods.