Physical properties of High-dispersion Leucite reinforced glass ceramic for CAD/CAM

Objectives:Dental glass-ceramics for CAD/CAM milling system like GN-I Ceramic Block(GC), ProCAD Block (Ivoclar Vivadent AG) or VITABLOCS MarkII feldspatic block (Vita Zahnfabrik) provide the esthetic single restorations and are becoming widely used in the clinical applications.We have developed the new glass-ceramic(GN-81) with the introduction of highly dispersed leucite crystal to GN-I Ceramic Block. The purpose of this study was to compare the flexural strength of GN-81 with those commercially available CAD/CAM ceramic blocks.

Methods: The specimens of the width (4±0.25)mm x thickness(1.2±0.2)mm x length(20.0±0.2)mm were prepared for GN-I Ceramic Block, ProCAD Block, VITABLOCS MarkII and GN-81 and polished according to ISO6872 for the measurement of three-point bending test. The dimensions of the specimens were measured to an accuracy of ±0.01mm. The breaking load for the specimens were measured at the test span of 15mm and cross-head speed of 1 mm/min and flexural strengths were calculated.  The data was analyzed by t-test (P<0.05).

Results:The results of flexural strength (three-point bending) are summarized in the following table. (n=10);.

Conclusion: GN-81 showed the highest flexural strength among the examined CAD/CAM blocks. The introduction of highly dispersed leucite crystal to CAD/CAM ceramic-block significantly improved its flexural strength.