The effect of spark plasma sintering on lithium disilicate glass-ceramics

Objectives. To evaluate the effects of spark plasma sintering (SPS) on the microstructure of lithium disilicate glass-ceramics. Methods. IPS e.max CAD glass-ceramic samples were processed using spark plasma sintering (SPS) and conventionally sintered (CS) as a comparison. Specimens were sintered at varying temperatures (T1: 840 degrees C, T2: 820 degrees C, T3: 800 degrees C), heating rates (HR1: 150 degrees C/min, HR2: 300 degrees C/min, HR3: 500 degrees C/min) and pressures (P1: 15 MPa, P2: 50 MPa, P3: 70 MPa). IPS e.max Press glass powder samples were densified at 750 and 800 degrees C (50 or 200 MPa pressure). Samples were characterized using XRD, HTXRD, and SEM and quantitative image analysis. Results. There was a significant increase in median crystal size (MCS) between the CS and the SPS T1 groups. A statistical difference (p > 0.05) in MCS between SPS T1 and SPS T2 groups was observed. The SPS HR3 sample produced a smaller MCS than the CS, SPS HR1 and HR2 groups (p < 0.05). The SPS P3 sample had a reduction in MCS compared with the CS group (p < 0.05). XRD of the SPS samples revealed major lithium disilicate/lithium metasilicate phases and minor lithium orthophosphate and cristobalite/quartz phases. Densified IPS e.max Press glass samples resulted in fine fibrils or graduated lithium disilicate crystals. Signcificance. The effects of SPS were used to refine the microstructure of IPS e.max CAD lithium disilicate glass-ceramics. Densification by SPS of IPS e.max Press glass resulted in textured and fine nano-crystalline microstructures. SPS generated glass-ceramic microstructures may have unique properties and could be useful in the production of CAD/CAM materials for dentistry. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.