What is lithium disilicate?

Introduced commercially in the late 1990s and refined through IPS e.max (Ivoclar) over the following decade, lithium disilicate occupies the space between weaker feldspathic porcelains and opaque zirconia. The crystalline structure , roughly 70% interlocking lithium disilicate crystals in a glass matrix , scatters light similarly to natural enamel. That optical quality is why prosthodontists lean on it heavily for anterior single units and three-unit bridges up to the second premolar.

For restorative general dentists, the material comes in two processing routes. Heat-pressed blocks allow custom layering and characterization before final glaze firing. Milled CAD/CAM blocks, available in fully crystallized or partially crystallized (blue) form, integrate directly into digital workflows: scan, design, mill, finish. Partially crystallized blanks mill faster and crystallize in a furnace cycle of roughly 25 minutes. Either route produces restorations in the 360-400 MPa flexural strength range, adequate for most single-unit and limited-span fixed cases.

The common clinical caution: lithium disilicate is adhesively dependent for thin preparations. Restorations under 1.5 mm rely on resin cement and proper etch-and-silane protocol to hit rated strength. Without that bonding protocol, fracture risk climbs. When a restoration fails at the lab remakes stage, the cause is usually preparation depth below spec or cement protocol deviation , not a material failure. Communication between dentist and lab at the design phase prevents most of those remakes.