Characterization of Lithium-Disilicate Glass Ceramic CAD/CAM Blocks

Objectives: Lithium-disilicate CAD/CAM blocks have become very popular in posterior dental restoration fabrication. We have developed a new block within this product family. The aim of this study was to evaluate the physical properties of lithium-disilicate based glass-ceramic CAD/CAM blocks.
Methods: Four materials were selected for analysis: 1) MGCCBZAD04 (GCCB04, GC Corp.); 2) IPS e.max CAD (EM, Ivoclar Vivadent); 3) CELTRA DUO (CE, DENTSPLY); and 4) SUPRINITY (SU, VITA). After cutting blocks for specimens preparation, EM and SU were heat-treated for crystallization using EP5000 (Ivoclar Vivadent) and Panamat Fire (DEKEMA) furnaces, respectively. To determine the crystal structures, 1 mm-thick, mirror polished samples were analyzed by X-ray diffraction (XRD) using Empyrean (PANalytical). For biaxial flexural strength (BFS) study, 12mm-diameter, 1.5mm-thick, mirror-polished samples were prepared. Bending test was conducted using universal testing machine AG-50KG (Shimadzu) with a cross-head speed of 1mm/min. (N=10). Data were statistically analyzed (ANOVA, Tukey's test).
Results: XRD analysis identified lithium-disilicate (Li₂Si₂O₅; LDS) as the major crystal phases of GCCB04 and EM, and lithium-phosphate (Li₃PO₄; LP) as minor phases. XRD data of CE and SU were identified with the peak pattern of LDS and lithium-metasilicate (Li₂SiO_3; LMS). The means BFS (SD) of group 1 - 4 were showed in the table. BFS of GCCB04 and EM was significantly higher than BFS of CE and SU.
(Means followed by same letter are not significantly different by Tukey’s test after one-way ANOVA, p<0.05)
Conclusions: This study confirmed that BFS varied significantly among the LDS based glass-ceramic materials. Newly developed GCCB04 exhibited promising physical properties as dental CAD/CAM product. Difference of BFS may be explained by crystal structures.