Fatigue damage of monolithic posterior computer aided designed/computer aided manufactured crowns

To analyse fatigue damage of monolithic computer-aided-designed/computer-aided-manufactured (CAD/CAM)-materials after loading with high masticatory forces in standardized posterior crowns in a mouth-motion-simulator.

For manufacturing of test specimens (5 groups, 16 specimens each), two corresponding Standard-Tessellation-Language-(STL)-data-sets (one for the teeth and one for the crowns) were designed. The teeth were CAD/CAM-milled of human third molars and the crowns of three different CAD/CAM composite blocks (Lava Ultimate,'LU'; Brilliant Crios'BC'; Cerasmart,'CS'), one polymer-infiltrated-ceramic network (Vita Enamic,'VE') and a control group of lithium disilicate ceramics (IPS e.max CAD,'EM'). Crowns were adhesively cemented with their corresponding luting system on the human teeth. Half of the specimens were light-cured ('LC') and the others were chemical-cured ('CC'). A mouth-motion-simulator (WL-tec, 2 Hz, 37 °C) applied dynamic cyclic loading between 50-500 N for a period of 1 million cycles. Afterwards, a dye penetration test (aqueous basic-fuchsine) revealed damage of test specimens. Each specimen was sectioned into four equidistant slices and the area without damage was measured with a digital microscope (Zeiss) and radial cracks at the cementation surface were assessed. Data were subjected to Tukey's test.

All specimens showed fatigue damage in the occlusal contact area. LU, BC and CS exhibited a significant greater area without damage compared to VE and EM (p < .05). EM and VE showed additional radial cracks at the cementation interface in both curing modes, whereas LU, BC and CS showed only radial cracks with chemical-cured luting cement.

Monolithic CAD/CAM composite crowns showed significantly lower fatigue damage, particularly if the luting system was light-cured.