Abstract
Background: The influence of the geometric features of composite cores on the fracture resistance of ceramic crowns has not hitherto been considered. The present in vitro study evaluated the effect of the Total Occlusal Convergence (TOC) of direct composite cores on the fracture resistance of the overlaying ceramic crowns. Materials and methods: Two groups of extracted premolars with dentine and composite foundations were prepared with 6o (n=10), 12 degrees and 18 degrees TOCs. The fracture resistance of the overlaying IPS e.max press crowns was assessed after thermocycling and cyclic fatigue loading. Results and discussion: All dentine-supported crowns showed a higher fracture resistance than the composite-supported ones (p<0.05). All crowns within each group showed comparable fracture resistance (p>0.05), yet those overlaying dentine foundation with 12 degrees TOC defied heavier loads (p< 0.05). Conclusions: Although composite cores provide lower support to the overlaying all-ceramics, no influence of the tested TOCs on crowns' fracture resistance was evidenced.