Investigation of the effect of b2o3 quantity on mechanical properties of lithium disilicate glass-ceramics

Lithium disilicate glass ceramics are used in the restorative dentistry because of their better mechanical properties and aesthetically resembling natural teeth appearance. In this study, the effect of microstructural change of B2O3 used as nucleating agent in the LS2 system on hardness-fracture toughness and bending strength values were investigated. Samples with different molar ratios of B2O3 were added into the starting composition and respectively, frit formation, homogeneous glass production and controlled crystallization processes were carried out. XRD & SEM analyzes were performed and 3-Point Bending Test was applied upon samples. In the process of controlled crystallization of LS2 glass ceramics which comprises nucleation and crystalisation growth steps, heat treatment and nucleating agent parametres are quite significant which affects the amount of crystal phase, crystal size and crack propogation mechanism in the LS2 glass ceramic microstructure. On the contrary to different nucleators used in the literature, the addition of B2O3 reduces the crystallization temperature and the sintering activation energy of the LS2 glass-ceramic system, which enables lithium disilicate (Li2Si2O5) crystals to form at low temperatures therefore LS2 glass ceramics can be produced with lower energy consumption.