Milling a crown in-office with chairside zirconia
Throughout my career, I have realized time and time again that there’s no single one “right way” to treat a patient; many different materials will allow us to do our jobs and meet the needs of the patient. Not every procedure requires the same materials, and not every patient will exhibit the same behaviors and preferences, so it’s my job to determine which of the many tools in my toolbelt will ensure the procedure is completed correctly and keep my patients as comfortable as possible.
Zirconia is one of those versatile materials. In the past, to be happy with the work I’d produced, I would need to spend a ton of time milling or send the work out. Even then, it could be difficult to achieve a desired aesthetic.
My patient in this case could not tolerate certain isolation devices, which typically would make it difficult to bond a restoration in place, but 3M Chairside Zirconia served as a solution because it was not necessary to bond. It’s also strong, and does not compromise on aesthetics.
This 60-year-old patient was in great overall health but came in with complaints of getting food stuck between Teeth #14 and #15, which caused irritation of the gums and great discomfort.
She already had a bridge on the upper left side of her mouth from #12 to #14, so instead of replacing the bridge, we agreed that she would come back to the office to restore the single restoration, which was a gold onlay crown (Fig. 1).
We began by taking pictures to verify the positioning of the upper cuspids, to ensure that we were keeping the buccal and lingual contours of the restoration as similar as possible to the original position. Then we prepared the tooth for a full crown.
After prepping the tooth and taking upper and lower digital impressions (Fig.?2), we drew the margin on the tooth we were designing and used a Cerec Omnicam machine from Dentsply Sirona to create the initial proposal (Fig. 3).
We evaluated the restoration to ensure the material was of adequate thickness. Occlusal contacts were checked to ensure we were not hitting too heavy, forcing the restoration to move distal and reopen the contact (Fig. 4). Then we checked the contours of the restoration to make sure they were similar to what the patient previously had for so long; our goal was to ensure that the feeling did not change for the patient. We created proper lingual and incisal interproximal contours and created a broad contact that would close the space, leaving a tight contact with no food trap (Fig. 5).
The blocks were placed in the milling unit and a bar code entered to ensure the proper amount of material shrinkage during the sintering process (Fig. 6). After 10 minutes of milling, the restoration was removed from the unit and we polished the zirconia material in its pre-sintered state using Luster Twist Polishers from Meisinger. We started with a course polisher, then a medium, fine and finally extra-fine polisher. We prefer polishing in a pre-sintered state because there is less of a pearl-like appearance after sintering, which provides a more natural look.
The material was then placed in the Cerec SpeedFire furnace, coronal side down, for 22 minutes. We then let it cool for three to five minutes before using an extra-fine polisher to repolish the surface, bringing final luster to the restoration. After sandblasting the intaglio surface of the restoration with aluminum oxide and cleaning the restoration with alcohol and air-drying it with oil-free air, the restoration was placed in the patient’s mouth.
We sandblasted the intaglio surface of the restoration one more time to remove the salivary contaminants before cementing with 3M RelyX Luting Plus Resin-Modified Glass Ionomer Cement. I prefer to use this cement because, in addition to being able to tack-light-cure the excess, it’s easy to use and clean up. We removed the excess cement with a scaler and a Gum Soft-Pick, then took a final photo and X-ray to ensure no cement remained (Figs. 7 and 8).
Every patient is different, all cases are different and, thankfully, all materials are different. No matter if it’s a cement, zirconia, hybrid ceramic—you name it, dentists today have the tools necessary to provide high-quality work while keeping patients happy. This is one material I’ll keep in my toolbelt.