Variations in Microstructural, Thermal, and Mechanical Properties of Different CAD/CAM Lithium Disilicate Reinforced Glass Ceramics
This study compared four CAD/CAM lithium disilicate-reinforced glass ceramic systems (IPS e.max CAD, Rosetta SM CAD, T-lithium CAD, and IRIS CAD) regarding their crystalline and microstructural characteristics, thermal properties, mechanical strength, and bonding to a resin cement. The crystalline and morphological characteristics of the ceramic microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), thermal behavior was assessed via differential thermal analysis (DTA). Mechanical properties were evaluated using a biaxial flexural strength test, and bonding to a resin cement was measured with a microshear strength test at distinct storage times. Data were evaluated using analysis of variance and Tukey HSD tests (α = 0.05). High peak positions corresponding to standard lithium metasilicate and lithium disilicate with similar intensities were observed for all ceramics in the XRD analysis. SEM morphological analysis showed differences in crystal characteristics among the ceramics after HF etching. The DTA thermograms showed a crystallization process ranging from 812-872°C among the different ceramic systems. The IRIS system showed the lowest flexural strength values, while bond strengths to resin cement remained comparable among materials, regardless of storage time. Most lithium disilicate ceramic systems demonstrated acceptable characteristics in the tests performed, except for IRIS, which showed shortcomings in crystal morphology and mechanical strength, along with inconsistent thermal behavior. These findings underscore the importance of careful material selection to ensure durable dental restorations.SUMMARY
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Schematic diagram of the specimens used for each experimental test. Abbreviations: XRD, X-ray diffraction analysis; SEM, Morphologic analysis with scanning electron microscopy; DTA, differential thermal analysis; BFS, biaxial flexural strength test; μSB, microshear bond strength test.
XRD diffractograms of the lithium disilicate ceramic systems in the pre-crystallized (A) and crystallized (B) states.
SEM micrographs of crystal morphology for each lithium disilicate ceramic system: (A) IPS e.max CAD, (B) Rosetta SM CAD, (C) T-Lithium CAD, and (D) IRIS CAD (10,000× magnification).
DTA thermograms as a function of increasing temperature over time (seconds) for each lithium disilicate ceramic system: (A) IPS e.max CAD; (B) Rosetta SM CAD; (C) T-Lithium CAD; (D) IRIS CAD; (β = 20° C/minute). Abbreviations: TG, nucleation/glass transition; TX, onset crystallization; TC, crystallization temperature; TF0, onset fusion; TF, fusion temperature.
Failure mode distribution (%) after μSBS test for each ceramic system and storage period.
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