Fatigue Resistance Evaluation of Lithuim Disilicate and Resin Nanoceramic

Objectives: Bulk fractures or cohesive fractures are frequent complications for ceramic crowns. The use of resin- based materials, in contrast to the brittle nature of ceramics, seems to be an alternative to posterior crowns, since these materials present simplified manufacturing and repair techniques. This study evaluates the fatigue resistance of 2mm monolithic CAD / CAM crowns made of resin nanoceramic and lithium disilicate reinforced ceramic, as well as the damage modes caused by the application of cyclic loading.
Methods: Twenty-six monolithic crowns (n = 13) were cemented to a composite resin replica of a prepared molar and subjected to cyclic load over 2 million cycles under maximum load of 350N, at a frequency of 2 Hz. The crowns presented no catastrophic failures or cohesive fractures. The crowns were embedded in epoxy resin and gradually grinded for damage analisys. Nanoceramic resin crowns presented no damage, outer cone cracks, inner cone cracks and radial cracks. Lithium disilicate crowns showed outer and inner cone cracks, some of the latter reaching the inner surface. Specimens were scored according to the severity of damage. Data was subjected to Mann-Whitney test (p = 0.462), which revealed no statistical difference in failure modes.
Results: Considering radial cracks and inner cone cracks reaching the cementation surface as failures, survival rates were 46,2% for lithium disilicate and 53,8% for resin nanoceramic crowns; no statistical difference.
Conclusions: We concluded that lithium disilicate and resin nanoceramic monolithic crowns presented comparable fatigue resistance, with no statistical difference between damage modes.