Comparison of fracture resistance of ceramic crowns supported by different abutment types

This study aimed to compare the fracture resistance of monolithic zirconia crowns and lithium disilicate crowns cemented on multi-unit, Ti-base and titanium copings on multi-unit abutments. 66 dental implants were embedded in auto-polymerizing acrylic resin. Three different types of abutments were used: Ti-base, multi-unit, and titanium coping abutments on multi-unit bases (n = 22/group). The specimens were subgrouped according to two different restorative materials: monolithic zirconia and lithium disilicate (n = 11/group). All of the crowns were screw-retained and the screws were tightened to the manufacturer's recommended tightening values. The specimens were subjected to cyclic loading of 50 N at 2 Hz for 100.000 cycles in distilled water and thermocycling between 5 °C and 55 °C for 5.000 cycles. Then, maximum fracture load was measured using a universal testing machine, and fracture patterns were examined under a stereomicroscope. Data were analyzed with ANOVA and Tukey's post hoc test. According to the results, there was a statistically significant difference between the types of abutments (p < 0.05). Additionally, significant differences were detected between the types of crown materials, with zirconia showing higher values than lithium disilicate (p < 0.05). Besides, all failures occurred as cohesive fractures within the crown material, no abutment or screw damage was observed. In conclusion, the abutment type and the material affected crown mechanics, with monolithic zirconia showing higher fracture resistance than lithium disilicate crowns. Furthermore, differences in abutment design affected the structural integrity of the restorations, underlining the importance of component selection in clinical decision-making.