Glass–Ceramics in Dentistry: A Review

Abstract

In this review, we first briefly introduce the general knowledge of glass–ceramics, including the discovery and development, the application, the microstructure, and the manufacturing of glass–ceramics. Second, the review presents a detailed description of glass–ceramics in dentistry. In this part, the history, property requirements, and manufacturing techniques of dental glass–ceramics are reviewed. The review provided a brief description of the most prevalent clinically used examples of dental glass–ceramics, namely, mica, leucite, and lithium disilicate glass–ceramics. In addition, we also introduce the newly developed ZrO2–SiO2 nanocrystalline glass–ceramics that show great potential as a new generation of dental glass–ceramics. Traditional strengthening mechanisms of glass–ceramics, including interlocking, ZrO2–reinforced, and thermal residual stress effects, are discussed. Finally, a perspective and outlook for future directions in developing new dental glass–ceramics is provided to offer inspiration to the dental materials community.

Nucleation Heat Treatment on the Crystalline Fraction and Crystal Morphology of Lamav Cad Lithium Disilicate

“…It is considered that the greater the aesthetics of ceramic materials, the lower their fracture resistance, since they present a greater glass phase and a lower crystalline phase, as is the case of glass-ceramics that are considered a special group of materials and have their microstructure composed of one or more crystalline phases embedded in glass matrix [3], with crystallinity ranging from 30-70% and crystals with needle morphology with dimensions from 3 µm to 6 µm [3,9]. This con guration results in a microstructure with lithium disilicate crystals interlocked lath-shaped that promote an increase in the exural resistance of these materials and result in the limitation of the propagation of the crack, because the conformation of the crystals make that, during the de ection of the crack, the path that the crack would have to go through increases [3,[9][10][11] and, consequently, consumes more energy.…”

“…However, other factors such as crystal size, phase type and porosity in uence the resistance of these materials [3], as well as the translucency which is dictated not only by the amount of crystalline phase but also by the size of the crystals and the refractive index of the two phases, the control of these factors can allow resistance and aesthetics [4]. Thus, with an appropriate design of the microstructure that can be modi ed by changes in time and temperature of the nucleation heat treatments and crystalline growth, it is possible to develop materials improving their properties from new microstructural designs [9,12,13].…”

“…Glass-ceramics result from the process of controlled crystallization, its properties being basically dependent on two factors, the composition of the reagents established and the heat treatment adopted [3,9,14], which when carefully modi ed can result in promising microstructural designs with excellent properties [9,12,13]. The conventional route of the glass-ceramics production process consists of four stages: melting, homogenization, induction of the internal nucleation by means of the nucleation heat treatment, and growth of the crystals with one or more heat treatments, which signi cantly affect the evolution of the crystalline fraction [15].…”

“…The conventional route of the glass-ceramics production process consists of four stages: melting, homogenization, induction of the internal nucleation by means of the nucleation heat treatment, and growth of the crystals with one or more heat treatments, which signi cantly affect the evolution of the crystalline fraction [15]. That is, the crystalline fraction is controlled through the nucleation and crystal growth stages, which can vary according to temperature and time for both conditions [9,12,13,16]. The heat treatments to which the glass-ceramic is submitted allow to obtain the desired microstructure and optimize the material properties, increasing the mechanical resistance of fragile materials [9,12,13].…”

“…That is, the crystalline fraction is controlled through the nucleation and crystal growth stages, which can vary according to temperature and time for both conditions [9,12,13,16]. The heat treatments to which the glass-ceramic is submitted allow to obtain the desired microstructure and optimize the material properties, increasing the mechanical resistance of fragile materials [9,12,13].…”