Fracture Resistance of Additively Manufactured Zirconia Crowns when Cemented to Implant Supported Zirconia Abutments: An in vitro Study

Purpose To compare the fracture resistance of implant-supported milled zirconia, milled lithium disilicate, and additively manufactured zirconia crowns. Materials and Methods Maxillary cast with a dental implant replacing right second bicuspid was obtained. Custom abutments and full-contour crowns for milled zirconia, milled lithium disilicate, and additively manufactured zirconia crowns (n = 10/group) were digitally designed and fabricated. The crowns were cemented to implant-supported zirconia abutments and mounted onto polyurethane blocks. Fracture resistance was determined by vertical force application using a universal testing machine at a crosshead speed of 2 mm/minute. Kruskal-Wallis test was used to analyze data and failure mode was determined for all the groups. Results Milled zirconia crowns demonstrated the highest median fracture resistance (1292 +/- 189 N), followed by milled lithium disilicate (1289 +/- 142 N) and additively manufactured zirconia (1243.5 +/- 265.5 N) crowns. Statistical analysis showed no significant differences in fracture resistance between the groups (p = 0.4). All specimens fractured at the implant-abutment interface. Conclusion Additively manufactured zirconia crowns demonstrated similar fracture resistance to milled ceramic crowns, when cemented to implant supported zirconia abutments. The results of this in vitro study signify the promising potential of additive manufacturing for the fabrication of all ceramic zirconia crowns.