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), 12o and 18o TOCs. The fracture resistance of the overlaying IPS e.max press crowns was assessed after thermocycling and cyclic fatigue loading. Results and discussion: All dentinesupported 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 12o 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.