Flexural strength and marginal fit of two types of lithium disilicate ceramics for crowns
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OBJECTIVES: To evaluate the flexural strength of 5 ceramic dental materials and to compare the marginal fit of crowns made with e.max press and a new experimental (EXP) press ceramic. MATERIALS AND METHODS: The materials tested for flexural strength included: E.max press, E.maxCAD, ENAMIC, Experimental press, and Experimental-CAD. Each group (N= 10) was tested using the Instron 5566A using 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 Experimental press. 5 crowns per material were obtained. A similar procedure was used with standard aluminum crown dies. Copings were waxed up and pressed: 3 copings of E.max and 6 copings of EXP. Eight measurements of marginal fit per restoration 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 and SD Flexural Strength values (MPa) per group were: E.max press: 486.96 (30.42). EXP press 378.16 (88.13). E.maxCAD 493.28 (55.2). EXP-CAD 420.63 (86.05). ENAMIC 157.59 (6.27). Mean and SD values for margin fit per group (Microns) were: E.max press 74 (19). EXP press 65 (19). CONCLUSIONS: E.max press has 28.8% higher FS than EXP press (P=0.0044). ENAMIC had the lower FS (as expected). EXP press had significantly lower marginal gap than E.max press by 12.2%.