| dc.description.abstract | All-ceramic dental crowns present a higher incidence of fracture and chipping when supported by dental implants as opposed to natural teeth. This study attempted to replicate the graded structural design of a natural tooth in an implant-supported all-ceramic crown to improve its fracture resistance by using additive manufacturing (AM). The purpose of this in vitro study was to compare the fracture resistance and ultimate compressive strength of implant-supported milled zirconia (MZr), milled lithium disilicate (MLD), AM zirconia (AMZr) and AM graded structural (AMGS) crowns. A maxillary cast with a dental implant replacing the right second bicuspid was obtained. Custom abutments and full-contour crowns were digitally designed. The STL files were used to mill 40 zirconia abutments and fabricate 10 crowns for each of the aforementioned 4 groups: MZr, MLD, AMZr and AMGS. The crowns were cemented to implant supported zirconia abutments in accordance with the manufacturer’s guidelines and mounted onto polyurethane foam blocks. The fracture resistance and ultimate compressive strength were determined for all the groups by vertical force application using a computer controlled universal testing machine at a crosshead speed of 2mm/min. Kruskal-Wallis test (α=0.05) was used to analyze the data and the mode of failure was determined for all the groups. Based on the experimental design, MZr revealed the highest mean value for fracture resistance (1330±111 N) and ultimate compressive strength, followed by MLD (1257±169 N), AMZr (1179±247 N) and AMGS (1169±163 N). However statistical analysis showed no significant differences in fracture resistance and ultimate compressive strength between the groups (p>0.05). All the samples fractured at the implant-abutment interface.
Within the limitations of this in vitro study, it can be concluded that AM crowns demonstrated similar strengths to milled crowns, when cemented to implant supported zirconia abutments. | en |
