Mike Skramstad, DDS
Sponsored by Dentsply Sirona
This patient presented with a RCT tooth that previously had a PFM crown. That crown fractured off and took some of the tooth structure with it.
Pre-op tooth #14
There was no decay present, excellent oral hygiene, and sufficient tooth structure to make a new buildup and crown for this patient
Since there was no enamel present, the tooth was already prepared for a conventional crown, and we needed to maximize resistance and retention form, a full coverage zirconia crown was chosen. Katana STML was the zirconia we planned to use because the rest of her arch was restored with IPS e.max CAD and we wanted to match the translucency as close as possible.
Preparation tooth #14
Since we had some extra time allocated for this patient (1 hour and 40 minutes), we also decided to use the Extra Fine Zirconia milling for this case. In addition to the 2.5 CS shaper bur and 1.0 CS finisher, there is a smaller .5mm CS finisher to create extra detailed anatomy and minimize finishing after the manufacturer process.
After anesthetizing the patient with 4% Articaine, the shade was taken for the restoration. It was determined that we would use an A2 Katana STML block. Once the shade was taken, the block information was entered into the Primemill and the touch process was initiated.
After starting the touch process, the patient information and Administration Phase was completed (designating Katana STML Milling for the restoration).
After a bonded buildup was completed, a full coverage restoration was then prepared with appropriate resistance and retention form for a cementable zirconia restoration. We prepped to the gumline with a 1.0mm modified shoulder (Winter Shoulder) and reduced occlusally by 2.0 mm to guarantee the final restoration had nice anatomy and at least 1.0mm thickness. No retraction cord was used in this case.
After prepping the tooth, the lower jaw, upper jaw and buccal bite were recorded with the CEREC Primescan in Acquisition Phase.
The models were processed and the automargination was evaluated. The CEREC Software did an excellent job with the margination and only minor modifications were necessary.
The CEREC software gave an excellent initial proposal and only minor adjustments were necessary to the contours, contact or occlusion.
Proposal Design Phase
After evaluating the proposal, the restoration was brought to the Manufacture Phase and sent to the CEREC Primemill. Since the touch process was completed earlier, the milling began immediately.
For this case we used the Extra Fine milling to complete the process. This milling takes substantially longer than the fine or fast milling, but the detail is improved greatly. The total mill time for the Katana STML restoration was 26:59. In most cases, the Extra Fine Milling takes closer to 19 minutes. Since this was such a large restoration, it took longer.
After Extra Fine milling was completed, the restoration was removed from the sprue.
Extra Fine Katana Mill out of mill
Since the anatomy was excellent with the Extra Fine Milling, no extra detail was required and just a minor prepolish completed in the presintered state.
Pre-polish Katana before Sinter
The EF milling definitely reduced the amount of time necessary on the presinter work. The restoration was automatically transferred to the CEREC SpeedFire furnace and sintering was completed in 18 minutes.
After Sintering, the functional surfaces were polished using Brasseler Dialite wheels and then stained and glazed in the CEREC SpeedFire furnace.
Final Stain and Glaze
After glazing and cleaning the restoration, the CEREC Zirconia was cemented conventionally using resin modified glass ionomer.
Final Restoration Extra Fine Katana STML #14
The total treatment time for this restoration can be broken down in the following way:
- Anesthesia, entering the block information in the Primemill, Pre-Touch process, and entering the patient and case information: 6 minutes
- Preparing the tooth and tissue management: 9 minutes
- Imaging and designing of restoration: 4 minutes
- Milling of the restoration: 26:59
- Removing restoration from sprue, defining anatomy and prepolish: 2 minutes
- Sintering of the restoration: 18:39
- Cooling of the restoration: 2 minutes
- Post sinter polishing of the restoration and stain/glazing: 5 minutes
- Glazing of the restoration: 9 minutes
10. Cooling of the restoration: 2 minutes
11. Cleaning and final cementation of the restoration: 5 minutes
TOTAL treatment time: 1 hour 30 minutes
The final restoration fit excellent and needed no post cementation adjustments whatsoever. The Extra Fine milling certainly extended the time compared to the Super Fast milling, but even with the extra milling time, the total appointment time fell into an acceptable range. The great thing about the Extra Fine Milling is that we have an option to create additional detail if so required for the case.
The CEREC Primemill not only brings speed to the appointment, but also versatility in milling strategies. In this case we chose extra manufacturing time in order to create a restoration with beautiful detail. This especially is useful when doing bridges as it created beautiful embrasures not possible with fine or fast milling.
When required the CEREC Primemill Extra Fast milling can create anatomy not seen before with conventional manufacturing with the MC XL. While this would not represent my daily workflow, the appointment time is still in a very acceptable range to produce an exceptional result. Options are the key.