Edge-Stability of the Novel Lithium Disilicate Glass-Ceramic Block for CAD/CAM

Objectives: Lithium disilicate glass ceramics are known as clinically useful dental materials from the viewpoint of aesthetics and high strength. In accordance with the dramatic progress of digital-dentistry, various materials for CAD/CAM have been developed. The purpose of this study was to evaluate the edge stability of the novel lithium disilicate glass ceramic block for CAD/CAM.
Methods: A 30-degree triangular prism was scanned using CEREC Omnicam (DentsplySirona). Initial LiSi Block (LS, GC Corp.), IPS e.max CAD (EM, Ivoclar Vivadent) and CELTRA DUO (CD, DentsplySirona) were fabricated into the prism shapes with CEREC MC XL (DentsplySirona) (n=8). Arithmetic mean surface roughness (Ra) and maximum height (Rz) of the specimen’s edge were measured by 3D Measuring Microscope (VR-5000, Keyence) after the grinding (Figure1, see arrow). To analyze crystal structure of each material, SEM (SU-70, HITACHI) observation was also carried out.
Results: In the following Table 1, different alphabets in the same column indicated significant difference (p<0.05, one-way ANOVA and Turkey test). After grinding test, LS showed lower Ra and Rz compared to EM and CD. SEM observation confirmed high density and fine crystal precipitation in LS glass matrix (Figure 2) and revealed that lithium disilicate crystals of LS were smaller than that of EM and CD.
Conclusions: In this study, the crystal size affects the edge stability of dental prosthesis, and it is suggested that Initial LiSi Block as a new lithium disilicate glass ceramic block has the accurate designed edge compared to other materials after the grinding.