Failure load of heat-pressed LDG table-top restorations with two preparation designs

Aim: to assess the fracture resistance of maxillary molars restored using heat-pressed lithium disilicate glass-ceramic (LDG) table-top restorations with two preparation designs. Methods: sixteen maxillary molars were randomly assigned to two groups (n = 8): Group 1 (G1) occlusal preparation for a 1 mm full-coverage table-top restoration with a 90° rounded shoulder margin; Group 2 (G2) 1 mm occlusal reduction with a marginal chamfer. Restorations were obtained by heat-pressed lithium disilicate glass-ceramic (LDG) and luted with Variolink II cement. The specimens were loaded to fracture after thermomechanical aging (1 250 000 cycles). A qualitative analysis on the type of fracture and a SEM analysis of marginal seal were conducted. Collected data were statistically analyzed (Mann Whitney U-test). Results: the mean load to fracture was 1796.58 ± 307.27 N in G1 and 1892.77 ± 379.40 N in G2. No statistical difference was found. Six specimens showed restorable fractures in G1, 4 specimens in G2. Thermomechanical aging did not produce marginal seal degradation. Conclusion: the two preparations designs for LDG table-top restorations exhibited a similar load resistance, type of fracture and marginal adaptation.