Restor Dent Endod.  2013 Aug;38(3):134-140.

Flexural strength and microstructure of two lithium disilicate glass ceramics for CAD/CAM restoration in the dental clinic

  • 1Department of Conservative Dentistry, Seoul National University School of Dentistry and Dental Research Institute, Seoul, Korea.
  • 2Clinic for Persons with Disabilities, Seoul National University Dental Hospital, Seoul, Korea.


There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent) and Rosetta SM (Hass), and to observe their crystalline structures.
Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi) and x-ray diffraction (XRD, Rigaku) analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05.
There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05). The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment.
IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.


Biaxial flexural strength; CAD/CAM restoration; Crystalline structure; Lithium disilicate glass ceramic

MeSH Terms

Dental Clinics
Dental Porcelain
Hot Temperature
X-Ray Diffraction
Dental Porcelain


  • Figure 1 Fixture with a piston-on-three-ball set up according to ISO 6872.

  • Figure 2 Field-emission scanning microscopy (FE-SEM) micrographs of fractured surfaces after biaxial flexural test (×10,000). Both ceramics display similar patterns of crystalline structure before heat treatment (upper micrographs) and after heat treatment (lower micrographs). (a) Microstructure of IPS e.max CAD in lithium metasilicate crystalline form; (b) Rosetta SM in lithium metasilicate crystalline form; (c) IPS e.max CAD in lithium disilicate crystalline form; (d) Rosetta SM in lithium disilicate crystalline form.

  • Figure 3 X-ray diffraction (XRD) patterns of IPS e.max CAD (a) and Rosetta SM (b) before heat treatment show high peaks at the locations denoting standard pure lithium metasilicate (JCPDS 29-0829). After heat treatment, the high peak positions in the XRD diagrams of the IPS e.max CAD (c) and Rosetta SM (d) are in agreement with those of standard pure lithium disilicate (JCPDS 15-0637).


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