A study into mechanical, aesthetic and adhesive aspects of lithia silica-based glass ceramics.

Lithia silica-based glass ceramics can be used in prosthetic dentistry to restore compromised or missing teeth. By modifying the chemical composition, silicates might vary in microstructure, formulations, processing methods, mechanical behaviour, and aesthetic appearance. Since the material selection might be also based on its mechanical properties, in the first investigation, the fracture resistance of CAD-CAM and heat-pressed lithium disilicate was evaluated and compared with regard to the translucency of the formulation and the processing method. By following a digital workflow, restorations are coarse in texture and opaque in aspect after milling. To make the surface compatible with the oral cavity, finishing procedures are necessary. In the second investigation, the efficacy of four finishing and polishing systems was tested on two lithia silica-based ceramics with standardized surfaces. After finishing, lithia silica-based restorations can be cemented with adhesive procedures. Micro-retentions and physico-chemical interactions are required to improve the adhesion between the resin cement and the intaglio surface. Since glass ceramics are hydrofluoric acid sensitive, in the third investigation, the effect of different etching protocols on the bond strength of two lithia silica-based ceramics with standardized surfaces was investigated.