Characterisation and Properties of Lithium Disilicate Glass Ceramics in the SiO₂-Li₂O-K₂O-Al₂O₃System for Dental Applications

Abstract

This work proposes four different glass formulas derived from the SiO 2 -Li 2 O-K 2 O-Al 2 O 3 system to investigate the effect of glass composition on their crystal formations and properties. Glass LD1 was SiO 2 -Li 2 O-K 2 O-Al 2 O 3 system with the addition of P 2 O 5 and CaF 2 as nucleating agents. In Glass LD2, a slight amount of MgO was mixed in order to increase the viscosity of the melting glass. Finally, the important factor of Si : Li ratio was increased in Glasses LD3 and LD4 with compositions otherwise the same as LD1 and LD2. The results found that P 2 O 5 and CaF 2 served as a nucleating site for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics. MgO content in this system seemed to increase the viscosity of the melting glass and thermal expansion coefficient including the chemical solubility. Increasing the Si : Li ratio in glass compositions resulted in the change of the microstructure of Li 2 Si 2 O 5 crystals.

Phase and microstructural evolution in lithium silicate glass‐ceramics with externally added nucleating agent

“…Among all‐ceramic dental restorations, alumina, zirconia, leucite, and lithium disilicate glass‐ceramics have been widely used . In the present scenario, lithium disilicate glass‐ceramic based crowns, veneers are preferred in dentistry owing to excellent mechanical strength of the material and aesthetics …”

“…. Many researchers found that by varying SiO 2 :Li 2 O ratio, lithium disilicate crystalline phase content could be varied, thus affecting the flexural strength of the material . Monmaturapoj et al observed that by keeping SiO 2 :Li 2 O ratio at 2.21 and carrying out heat treatment at 800°C, biaxial flexural strength of 490 MPa and chemical solubility (in 4 % acetic acid solution) of 28 µg/cm 2 over a period of 16 hrs was achieved.…”

Roles of iron and lithium in silicate glasses by Raman spectroscopy

“…The practical importance of lithium silicate glass and ceramics has drawn much attention of the researchers to these systems. Lithium di‐silicates as ceramics are the most promising materials for dental restorations, dental crowns, tooth veneers, and so forth on account of its colour being similar to natural teeth and its high mechanical strength …”

Influence of Al2O3 and B2O3 on Sintering and Crystallization of Lithium Silicate Glass System

“…. However, GCs derived from binary Li 2 O–SiO 2 system exhibit some unfavorable characteristics in terms of their mechanical strength and chemical durability which hinder their use in several technological areas . Therefore, nonstoichiometric or multicomponent compositions have been developed to overcome this problem.…”