Zirconia crowns have become increasingly popular in the last decade. Because zirconia restorations provide strength and lifelike esthetics, most dental practices are shifting away from traditional PFM crowns and toward the use of zirconia for creating fixed dental restorations. Furthermore, zirconia is an extremely durable material that can withstand prolonged forceful chewing and grinding. Zirconia restorations can last a patient's entire life if properly cared for. Because zirconia crowns are new, many dentists are hesitant to use them or learn how to properly cement them into their patients' mouths. Understanding how to properly cement and bond zirconia is one of the most important aspects of placing successful zirconia restorations.
Steps for Zirconia Crown Cementation:
Make Restoration Plans
After try-in, sandblast the restoration with 20 microns of aluminum oxide. Many dental technicians recommend sandblasting at a pressure of 2.5 bars (20-25 psi) to roughen the surface to be bonded without making it visible to the naked eye. Obviously, the part of the restoration that does not require bonding, such as the outside of a veneer or the dummy of an adhesive bridge, has to be protected from the effect of the abrasive grains. Prior to the operation, a colorant (waterproof marker pen) should be applied to the area to be sandblasted. Because the color fades during sandblasting, it is easy to verify that the entire adhesive surface has been abraded. If sandblasting is performed in the laboratory prior to try-in, use NaOCI to clean the saliva contamination and rinse with water. Cleaning with phosphoric acid is not recommended.
Dry with oil-free air after cleaning with alcohol.
Prepare the Tooth
Remove the temporary restoration. Clean the prepared tooth mechanically with pumice paste. Make certain that any residue (such as temporary cement, desensitizers, astringents, and disinfectants) is completely removed.
Cement the tooth in place.
Discard a small amount of cement onto the mix-pad to ensure a perfect mix.
Apply cement directly to the crown.
With finger pressure, firmly seat the crown.
For 1-2 seconds, tack the cure. Extending the recommended tack cure time will make clean-up extremely difficult. For a controlled curing time, use an LED curing light.
With a scaler, remove the excess cement while holding the crown in place.
The Final Cure
Light cure the tooth for 20 seconds per surface, or dark cure for 6 minutes from the start of the mix. As needed, finish and polish the restoration.
Avoiding Complications During the Cementation Process
During the cementation process, avoid any phosphoric acid contact with the zirconia restoration.
The acid's phosphate ion greatly reduces any potential bonding to the zirconia.
Prophy paste should not be used to clean the tooth preparations.
Some prophy pastes contain emollients and fluoride, which can be harmful and cause crowns to fall out. Use pumice flour and water.
If you are struggling to remove phosphate groups from zirconia, be sure to use a proprietary solution such as Ivoclean. Before rinsing, leave the solution on the crown for 20 seconds. The crown should then be air-dried before bonding.
When a procedure is performed incorrectly, it can have serious consequences for the patient's health and well-being. What makes Zirconia dental crowns so appealing is that they offer a superior alternative to other options, whether ceramic or porcelain. When placed in a patient's mouth, they have smooth and attractive surfaces that bond with other dental materials. With these characteristics in mind, you can be confident that your Zirconia dental crowns will perform optimally.