The purpose of this study was to evaluate the fracture resistance and investigate the failure mode of monolithic anterior crowns made from BruxZir anterior and e.max CAD having two thicknesses of finish line.
A total of 20 anterior ceramic crowns were divided into two groups (n = 10) according to the type of ceramic material. Group 1 monolithic lithium disilicate (IPS e.max CAD) crowns and group 2 monolithic zirconia (BruxZir Anterior) crowns. Each group was further subdivided into two subgroups (n=5) according to finish line thickness. Subgroup 1: 0.8 mm finish line and subgroup 2: 1.2 mm finish line. Two metal dies with 0.8 and 1.2 mm finish line thicknesses were designed and milled. Construction of ceramic crowns then followed. The dies were duplicated into epoxy dies over which the crowns were adhesively cemented. Each assembly was loaded in a universal testing machine where fracture resistance test was done. Failure modes were analyzed under digital microscope.
There was no significant difference in fracture resistance values within BruxZir crowns with 0.8mm and 1.2mm finish lines while e.max crowns with 1.2mm finish line showed significantly higher fracture resistance than with 0.8mm finish line. BruxZir showed significantly higher fracture resistance than e.max.
It was concluded that: All anterior crowns constructed from zirconia and lithium disilicate revealed fracture resistance values above the range of normal masticatory forces with higher significant values for zirconia crowns. Lithium disilicate crowns are recommended to be used with finish line thickness of 1.2 mm rather than 0.8mm.