Studies of crystal phase formations in high-strength lithium disilicate glass–ceramics

Microstructural evolution and physical behavior of a lithium disilicate glass–ceramic

“…Similar to past studies [26,41,44] Figure 20 for the possible reaction mechanisms when IPS e.max® CAD was heat-treated. This activity was in accordance with earlier findings [26].…”

“…Scanning electron micrographs of IPS Empress® 2 revealed that the microstructures of lithium disilicates were elongated crystals with a mean grain length and diameter of 5.2 µm and 0.8 µm respectively [15]. In contrast to IPS Classic®, for which uncontrolled devitrification of leucites occurred only on the surface [27,28], the controlled crystallization of IPS Empress® 2 ensured that nucleation and crystal growth of lithium disilicates propagated uniformly throughout the bulk structure during heat treatments [26,28]. The nucleation in IPS Empress® 2 was achieved with the aid of special additives (e.g., P 2 O 5 , TiO 2 and ZrO 2 ) [29,30].…”

“…Unlike the binary lithium disilicate system that was first developed by Stookey (1959) [25], the IPS Empress® 2 was derived from a multi-component system, formulated from [13,26]. Scanning electron micrographs of IPS Empress® 2 revealed that the microstructures of lithium disilicates were elongated crystals with a mean grain length and diameter of 5.2 µm and 0.8 µm respectively [15].…”

“…For example, the orientation and saturation of crystals within a glass-ceramic relied on the proximity between the nucleating sites and on the locations and numbers of nucleating agents, whose development could be induced at random or at the glass-ceramic's center of mass or its periphery and whose distribution might or might not be homogenous in bulk [26,57,58].…”

“…Generally, explosive growth of lithium disilicates occurs only when the maximum formation of lithium metasilicates has ended [26]. Numerous authors have postulated that lithium metasilicates serve as catalysts for lithium disilicate crystallization, while others argue that lithium metasilicates are unstable intermediates, and their nuclei serve as centers for epitaxial growth of lithium disilicate crystals [38,40,42].…”