A mastication simulation test involving 1.2 million simulated thermocycles at 70 Newtons of force was conducted on Crystal Ultra nanoceramic hybrid dental restorative material in November of 2008.
One of the unique properties of Crystal Ultra is that it is the only hybrid material approved today to be strong enough for use in creating bridges and full‐arch restorations, so we choose to do the simulation with three‐unit bridges in order to test the material in a more demanding stress and wear profile.
Methodology: 10 identical three‐unit full‐anatomical bridges were milled from two 18mm thick discs of Crystal Ultra material, color A2. The thinnest portion of the designs were 0.2 to 0.3mm located at the center of the fissures and the cervical margins. The milled bridges were polished and numbered, and attached to a custom‐made post using a variety of bonding solutions. Thermocycling was conducted simultaneously with 1.2 million 70 newton load cycles at 1.2 Hertz using an atagonist sphere that was lifted 3 MM between cycles. All samples were examined under magnification and photographed, and three samples were selected for further examination using an Scanning Electron Microscope the next day.
Conclusion: After 1.2 million simulated “bites,” representing five years in the mouth, no fractures or excessive wear was evident even after study with a scanning electron microscope at 1000 X magnification. Additionally, on two samples which exhibited minor defects prior to the test, neither the load cycles nor the thermal stresses changed or worsened the defects. Crystal Ultra exhibited properties of abrasion that are very close to that of enamel.
Comparative Analysis: A similar 1.2M mastication test was conducted on Empress 2 dental restorative material which resulted in cracks and chips that were visible to the naked eye. The Empress 2 study was conducted by the University of Munich in 2002 using a lower 50 Newton load.
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