I consider myself somewhat of a techno-junkie when it comes to the way I practice dentistry. The more technology, the better! Whether its digital x-rays, hard and soft tissue lasers, or CAD/CAM digital impressions and milling, technology has truly made dentistry more exciting, more precise and more immediate. This article outlines the use of the CEREC Omnicom to take a digital impression for a simple e.max monolithic crown on tooth 47 and the use of CEREC Connect to send a digital file to my laboratory in Montreal.
Again, the restoration chosen for this patient was an e.max (Lithium Disilicate) monolithic crown on tooth 47. The entire clinical procedure from prepping to cementation will be discussed as well as preparation guidelines for an e.max crown. In addition, the laboratory component will be discussed from the point of when the CEREC Connect file is received, to the complete fabrication of the restoration.
PRE-SCAN AND ISOLATION
Once the patient is anesthetized (if necessary) and the shade has been selected for the restoration, the right quadrants are isolated using the iZolation™ dry field retraction system (Fig. 1).
FIGURE 1./201404071507390vvstcpnsqcea3n55knikdn45.jpg)
This system is perfect for retracting the cheek, tongue and lips and allows for a dry field to achieve an accurate digital impression (scan) to be performed with ease. Once logging onto our Cerec computer for Cerec Connect, the patient’s information is entered, while both the tooth and restoration type are selected, and then a scan of the opposing dentition, is completed (1st quadrant) from 17-13 (Fig. 2).
FIGURE 2./201404071507391vvstcpnsqcea3n55knikdn45.jpg)
The scan is completed without any illumination other than from the camera. This has been found to provide the most accurate scan. To prevent fogging, it is very important to ensure the camera has had a chance to warm up. Scanning from 17 – 13 is completed so that the opposing tooth is captured for occlusion, while the area from 15-13 is captured so upper, lower and buccal scans of teeth in occlusion, can be stitched together.
PREPARATION
Once isolated with rubber dam, the e.max preparation is carried out to the specifications by Ivovclar (Fig. 3).
FIGURE 3./201404101040370ly4kcumrb0szec55dbuzpm2q.jpg)
It is quite simple. Preparation of the tooth to manufacturer’s guidelines, results in the restoration performing as expected. For years, we placed PFM restorations, which are known to have flexural strength of approximately 75-90 MPa and we, as dentists, were fine with that–all the more reason, to choose this wonderful life-like monolithic material, far surpassing the flexural strength of traditional PFMs at 360-400 MPa. Once again, the strength of the crown comes, in part, from proper preparation. Having said that, every time I reduce a tooth, I choose burs based on their dimensions so that 100% of the time, I can ensure that my preparations match the guidelines for that particular material. In this case, I used a KUT 330 (Dental Savings Club) pear shaped bur, with a known head length of 2mm, allowing me to prepare the occlusal surface with depth cuts and decoronate the surface evenly (Figs. 4 & 5).
FIGURE4./201404071507392vvstcpnsqcea3n55knikdn45.jpg)
FIGURE 5./201404071507403vvstcpnsqcea3n55knikdn45.jpg)
Once completed, a modified flat end tapered diamond (Brasseler 847KR) with the tip diameter of 1 mm, was chosen to reduce the tooth completely and prepare the margin area. Again, according to manufacturer’s instruction, the e.max margin should either be a shoulder or modified shoulder (slightly rounded) to a depth of 1mm. Once the depth cuts are done on the labial and lingual surfaces, the depth cuts are joined to form a very smooth reduction, creating a perfect margin. The reduction is continued through the proximal contacts. After the prep is complete, smoothing the preparation and rounding the occlusal surface edges with enhance points and cups, will ensure that the final scan and fit of the e.max crown will be perfect.
FINAL DIGITAL IMPRESSION (SCAN)
Satisfied with the completed preparation, margin visualization for the final scan is a must. My choice is always troughing rather than using retraction cord as it is much gentler to the periodontal complex and can be done without any anesthesia on the gingiva. It allows for a completely dry field without the use of astringents, 99 percent of the time. In the event that any astringent is necessary, my choice is always Viscostat Clear, which is 25 percent Aluminum Chloride (Ultradent), otherwise, if using Viscostat or Astringident (Ferric Sulfate), brown stain is likely to appear at the margin area. Troughing is performed with my Waterlase iPlus hard/soft tissue laser in a matter of seconds. Figure 6 shows the completed preparation and troughed margins, allowing the final Cerec scan to be completed with ease.
FIGURE 6./201404071507404vvstcpnsqcea3n55knikdn45.jpg)
Once again, the area is isolated with the iZolation system and the final scan is performed. I have found the best scanning technique is to begin the scan at the distal-most tooth in the arch. This is done about 2-4 mm away from the tooth surface, scanning the occlusal to cuspid area, then rolling the camera to the labial surface, scanning backward towards the molar area again, then rolling over to the lingual surface and scanning from the molars to the cuspid again. I then pause to examine my scan for deficiencies and concentrate on those areas, if needed. After I am satisfied with the completed scan, I then remove the iZolation and position the patient in occlusion and proceed to scan the buccal bite, concentrating primarily on the area from the second bicuspid to canine.
CEREC CONNECT
Once the scanning has been completed, the scans are spliced together using the buccal bite scan. From there, the working arch scan is trimmed and the margin area is identified (Fig. 7).
FIGURE 7./201404071507405vvstcpnsqcea3n55knikdn45.jpg)
From here, the Cerec connect program guides the user in identifying the lab of choice to be used, the instructions and the case file. Once sent to the lab electroniclly, a confirmation email is sent to the user that the case was in fact sent. Then once the lab has accepted the case, another email is sent to the user. From here, it is now up to the laboratory to design and complete the desired case.
LABORATORY
As a modern lab, on the cutting edge of technology, VIVACLAIR CANADA dental laboratory is fully equipped to receive and construct every possible demand in dentistry.
RECEIVING DIGITAL IMPRESSION AND MODEL
When Dr Rykiss sent his digital impression, we received an email from Cerec Connect to download the impression file. This is a great advantage in dentistry, making the transfer between dentist and laboratory faster, more efficient and more precise in a very easy, user friendly way, from all over the world to any destination.
After checking the digital impression with the defined margin and the articulation, I approved and sent the file to Infinident Company. Infinident will fabricate and send back to me, in approximately two days, the physical model articulated to the lab (Fig. 8).
FIGURE 8./201404071507416vvstcpnsqcea3n55knikdn45.jpg)
DESIGNING, MILLING AND CUSTOMIZING THE CASE
Once I’ve received the model, I designed and milled the crown in wax as full contour on my CAD CAM (Fig. 9).
FIGURE 9./201404071507417vvstcpnsqcea3n55knikdn45.jpg)
Personally, as a dental technician, I’ve acquired trust and confidence in the precision of new dental technologies, but I believe that every case should be studied and worked differently. In the case of Dr Rykiss, I chose to mill it in wax so I can give more characterization and texture to the morphology.
FINISHING PROCEDURE
Once the waxup was ready, it was invested then pressed using an HT A1 e.max ingot.
After divesting and sand blasting, the surface was cleaned by using Invex etching liquid in an ultra-sonic machine for twelve minutes. The crown was then sandblasted again.
Once the crown was clean, the adaptation of the crown was checked and verified, as well as the occlusion and proximal contact on the articulated model.
When all required aspects were reached, only then was the staining procedure started.
The shade of natural tooth in this case was A2. A lighter color was chosen, translucent HT A1 ingot, to control and manipulate the shade and to bring it in harmony with the existing teeth.
With Universal shades, the crown was stained, changed from A1 to A2, and now the crown had the shade of the patient’s natural teeth. To give the crown life, it was stained slightly in some areas to achieve different effects using some blue, grey, orange, and white stains.
The crown was glazed without adding any porcelain, making it completely monolithic, which keeps its strength at 400 MPA as a full monolithic lithium disilicate (Fig. 10).
FIGURE 10./201404071507428vvstcpnsqcea3n55knikdn45.jpg)
The crown was etched with hydrofluoric acid 5 percent for one minute, cleaned and ready for cementation.
TRYIN AND CEMENTATION
Once the case returns from the lab, the patient once again is anesthetized, the temp crown is removed, and the preparation is cleaned with Cavity Cleanser (Bisco) and pumice mixture, ensuring all debris is removed prior to try-in. After the crown is tried in and occlusion is checked, it is repolished using Brasseler’s Lithium Disilicate polishing kit, thoroughly cleaned using Ivoclean (Ivoclar) and acid etched with Porcelain etchant (Bisco). If, in fact, the e.max crown was to be bonded, the crown would also be silanated, and a bonding agent would be applied to the tooth. I could choose Bisco’s 2 bottle silane, and then Allbond Universal (Bisco). The crown would be cemented with Duolink Universal (Bisco) – a dual cure cement that can be flash set for quick cleanup. I truly appreciate the ease of cleanup with this cement.
My cementation protocol has changed though, to include a cement called Ceramir C&B (Doxa). Ceramir is truly a one-of-a-kind cement that is truly bioactive. Its bioactivity is measured by its ability to form hydroxyapatite at the tooth crown margin when in contact with phosphates from the oral cavity. Clinically, this may cause a protective layer at the crown tooth margin. Ceramir is the only dental cement which is a calcium-aluminate based formulation, causing the cement to set at a very high pH for permanent acid resistance. Nano-structural integration is used for adherence as opposed to traditional bonding methods. The cement exhibits no shrinkage, expansion, or solubility, and thrives in both heat and moisture. The protocol for cementation of an e.max crown is to acid etch with HFl acid (20 sec) alone, then cement, without using bonding agents or silane. All other crowns including PJC, PFM, Zirconium or FMC, do not require etching, so they are just simply cemented in place, once the crown surface has been cleaned following try-in. Again, no bonding agent is used. The material is activated, placed in amalgamator for five to eight seconds, and then applied into crown. In this case, we placed the crown onto the prep and held in place with the patient biting on a cotton roll for three minutes. After three minutes, the material becomes rubbery, and the ribbon-like excess can be easily removed with an explorer or scaler with ease as seen in Figure 11.
FIGURE 11./201404071507429vvstcpnsqcea3n55knikdn45.jpg)
Full set is achieved in five minutes. By virtue of its bioactivity and ease of use, Ceramir has become a
n invaluable addition to my crown and bridge regimen. Figure 12 shows the completed crown in place.
FIGURE 12./201404071524100vvstcpnsqcea3n55knikdn45.jpg)
CONCLUSION
Dentistry in the 21st century has truly revolutionized the way we can choose to practice. No longer do we have to use sticky VPS impression materials in the patient’s mouths to render an exact impression of our preparations. We can now rely on digital impressions to impart accuracy to the same degree and beyond. Furthermore, laboratories can now accept our digital impressions and use them to fabricate any restoration we want in a much more timely fashion.OH
Dr. Rykiss maintains his private practice in Winnipeg, MB. He is a graduate of the University of Manitoba as well as a graduate and Mentor at the Nash Institute for Dental Learning in Charlotte, N.C. He has his Fellowship with the International Academy for Dental Facial Esthetics, an associate Fellowship from the World Clinical Laser Institute, and is a member of the ASDA and CAED. He teaches, lectures, and writes articles on restorative, cosmetic dentistry, and hard and soft tissue laser use.
Bassam Haddad is a dental technician for more than 23 years. He acquired a comprehensive knowledge in various systems of dental technology with the greatest masters of dental art in the world. He has authored several local and international articles on aesthetic and restorative dentistry and lectured at several dental conferences. He is known to give passionate hands-on courses where he shares his knowledge, own techniques and discoveries for a natural and aesthetic result. Bassam is member of the AACD, the EACD and an honor member of the Society of Esthetic dentistry in Romania. He holds VIVACLAIR CANADA dental laboratory in Montreal.
