Impact of thermal shock cycles on mechanical properties and microstructure of lithium disilicate dental glass-ceramic

In the present paper, we report results on the impact of thermal shock cycles on mechanical properties and microstructure of lithium disilicate dental glass-ceramic relevant to the production process. A distinct reduction of the bending strength is observed after suffering more than five thermal shock cycles. The crystal, morphological and atomic structural characteristics before and after the thermal shock were detected by X-ray diffraction, infrared spectroscopy and field-emission scanning electron microscopy. Furthermore, theoretical calculations, based on density functional theory, were performed on models for the distorted and undistorted lithium disilicate crystal lattices. We show that the morphological and mechanical changes can be attributed primarily to the distortion of the Si-O-Si structural unit of the lithium disilicate glass-ceramic.