It has long been known that porcelain, the most used exterior material for most dental restorations in the past, is a highly abrasive material and wears down the opposing dentition over time. Under the microscope, natural tooth enamel is a porous material, and when ground on by the sawtooth surface of porcelain, the natural dentition wears over time.
Zirconia, however, is made from very fine round particles and when sintered at high temperatures, the smallest particles combine and fill in spaces to create a glassy smooth non-porous surface. As a result, polished zirconia is said to have 1000 to 10000 times better wear characteristics compared to porcelain.
Both natural tooth enamel and lithium disilicate are comprised up of very long sharp needle-like hydroxy-apatite crystaline structures, and have similar wear characteristics. Of all of the ceramic materials, however, polished and glazed zirconia seems to have the best wear characteristics.
A number of studies and lab results in recent years have confirmed and quantified the excellent wear characteristics of zirconia compared to enamel, lithium disilicate and porcelain:
- "When natural tooth meets smooth zirconia (like wood against glass), no abrasion occurs. The abrasive nature of any material is determined by its degree of surface polish and inherent density. The "softer" enamel will glide over polished, much harder zirconia without wear. By contrast veneer porcelain (or even metal) will cause wear on natural dentition due to its highly porous structure
which acts like sandpaper. Veneer porcelain is 1000 times more abrasive..."
-- Zirkon Zahn, Switzerland, 2009
- "The results after 100,000 cycles show that the volume loss is virtuall identical..."
-- University of Alabama, January 2010
- "The glazed ceramic surface produced significantly less enamel wear compared to polished ceramic surface (p=0.0157). Conclusion: Within the limitations of this study, glazed ceramic surfaces should be preferred when the restoration antagonist is natural tooth."
-- University of Alabama presented at AADR, March 2010
- "The polished zirconia caused less wear to the enamel abrader than the as processed zirconia."
-- University of Michigan, 2003