FLEXURAL STRENGTH AND MARGINAL FIT OF TWO TYPES OF LITHIUM-SILICATE

Objectives: To evaluate the flexural strength of two types of lithium disilicate based ceramic dental materials and to compare the marginal fit of crowns made with e.max press and a LiSi Press ceramic.
Methods: The materials tested for biaxial flexural strength included: IPS e.max Press and CAD (Ivoclar Vivadent), Initial LiSi Press and CAD (GC Co.). Each group (N= 10) was tested using the Instron 5566A and the piston-on-three- balls test. For the crown fit experiment an Ivorine tooth was prepared with a chamfer finish and used as the master die. Wax up crowns were made on the die and pressed with e.max Press and the LiSi Press. Five full crowns were obtained per material. A similar wax up procedure was used with standard aluminum crown dies to make copings. Six copings were pressed by of e.max Press and LiSi Press. Eight measurements of marginal fit per crown were obtained with an optical microscope at 200×. The data was analyzed using ANOVA and a post hoc Tukey-HSD test (significance level = 0.05).
Results: Mean (SD) flexural strength values (MPa) per group were: e.max Press: 486.96 (30.42), LiSi Press 378.16 (88.13), e.max CAD 493.28 (55.2). LiSi CAD 420.63 (86.05). Mean (SD) values for margin fit per group (μm) were: e.max Press 74 (19) and LiSi Press 65 (19).
Conclusions: E.max Press had 28.8% higher biaxial flexural strength than LiSi Press (P=0.0044). LiSi Press had a significantly lower marginal gap (12.2%) than e.max Press.