Zirconia crowns have gained popularity over the past decade. Most dental practices are switching from the conventional PFM crowns and moving towards the use of zirconia for creating fixed dental restorations because zirconia restorations provide strength and lifelike esthetics. Additionally, zirconia is an extremely durable material and can withstand forceful chewing and grinding over an extended period of time. If properly maintained, zirconia restorations can last a patient’s lifetime. Because of its newness, many dentists refrain from using zirconia crowns or learning how to properly cement them into their patient’s mouths. Knowing how to properly cement and bond zirconia is one of the key factors to placing successful zirconia restorations.
Zirconia Crown Cementation Steps:
- Sandblast the restoration with 20 microns of aluminum oxide after try-in. Many dental technicians advise sandblasting at a pressure of 2.5 bars (20-25 psi), so that the surface to be bonded becomes somewhat rougher without this being 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. It is also advisable to apply a colorant (waterproof marker pen) to the area to be sandblasted prior to the operation. The color disappears during sandblasting, making it easy to check that the entire adhesive surface has actually been abraded. If sandblasting is done in laboratory before try-in, clean the saliva contamination with NaOCI and rinse with water. Do not use phosphoric acid for cleaning.
- Clean with alcohol and air dry with oil-free air.
Pretreat the Tooth
- Remove the provisional restoration. Mechanically clean the prepared tooth with pumice paste. Make sure any residue (i.e. temporary cement, desensitizers, astringents, disinfectants) is completely removed.
Apply Cement and Seat the Tooth
- Discard a small amount of cement onto the mix-pad to ensure a perfect mix.
- Dispense cement directly into the crown.
- Firmly seat the crown with finger pressure.
- Tack the cure for 1-2 seconds. Do not exceed the recommended tack cure time, otherwise clean-up will be extremely difficult. For a controlled curing time, use an LED curing light.
- Remove the excess cement with a scaler while holding the crown in place.
- Light cure the tooth for 20 seconds per surface or wait 6 minutes from the start of mix for a dark cure. Finish and polish the restoration as needed.
Complications to Avoid During the Cementation Process
- Avoid any contact of phosphoric acid with the zirconia restoration during the cementation process. The phosphate ion in the acid greatly reduces any potential bonding to the zirconia.
- Do not clean the tooth preparations with prophy paste. The emollients and fluoride in some prophy pastes can be negative and cause crowns to come off. Use flour of pumice and water.
- If you are struggling to remove phosphate groups from zirconia, be sure to use a proprietary solution such as Ivoclean. Leave the solution on the crown for 20 seconds before rinsing. The crown should then be air-dried before it is ready to bond.
If you ever experience cementing complications with a zirconia restoration, call our lab directly to discuss your specific case with our expert technical team. DDS Lab’s technical team is ready to help solve any issues regarding zirconia crowns or bridges and will work with your office to find the best solution.