Cement-Free Esthetics: The Exceptional Difference
This technology changes the long-standing norms
By Conrad J. Rensburg, ND, NHD
With the ever-increasing amount of new technologies, products, and procedures available to dental laboratories today, it is becoming exponentially more difficult to differentiate between the exceptional and the average. Not only is it important for laboratories to choose carefully before investing, but it’s even more essential for laboratories to be cautious before they introduce these technologies to their customers.
After fabricating multiple cases using NobelProcera® Full Contour Zirconia (FCZ) and NobelProcera Angulated Screw Channel (ACS) technologies, the author believes these innovations truly have the ability to enhance a laboratory’s product line and provide a competitive edge within the market. The use of these technologies will help change many of the long-standing norms of cementing crowns to abutments on implants. This type of offering has been in great demand by an industry attempting to move away from cement-retained crowns on implants. In the past, the restorative team would encounter a few disqualifying issues when attempting to restore using screw-retained prosthetics: screw access causing esthetic issues in the anterior, weakened occlusal ceramics due to screw access, and in some cases accessibility problems.
The ASC correction technology enables the restorative team to reposition the screw access by up to 25 degrees without the use of a correction abutment. This repositioned screw access enables us to achieve better accessibility, stronger occlusal tables, and lingual access on anterior screw-retained crowns.
The use of FCZ provides us with the ability to digitally process posterior monolithic zirconia and hybrid anterior screw-retained crowns. The system features a metal adapter securing the zirconia one-piece crown into the implant. The monolithic design successfully addresses many of the strength concerns that existed when using layered screw-retained restorations.
To process an FCZ crown, the laboratory needs a traditional implant-level impression to allow for the technician to fabricate a soft tissue cast (Figure 1.). At the time of this publication, fully digital options are in planning and testing
The laboratory places an FCZ wax-up sleeve into the soft tissue model and performs a screw-retained diagnostic wax-up. This wax-up will be digitally scanned with the NobelProcera System and the file sent to NobelProcera manufacturing for exact copy milling. It is crucial to establish accurate emergence and final contours in this wax-up stage (Figure 2).
The diagnostic wax-up is attached to a NobelProcera abutment wax-up holder and digitized using the NobelProcera 2G Scanner. Screw access can be corrected by implementing the ASC technology; this correction amount can be adjusted in the NobelProcera Software. After access correction, a digital cutback is performed to facilitate the porcelain application on the facial (Figure 3).
The FCZ prosthesis is now milled from the digital files sent to NobelProcera. The prosthesis is returned to the laboratory in a sintered and color-infiltrated state. The FCZ crown is an exact copy of the wax-up with digital ASC correction and cutback adjustments. Minor adjustments are made to the FCZ substructure. Then, zirconia-bonding medium and ceramics are applied using traditional protocols (Figure 4 through Figure 6).
The hybrid-layered monolithic crown is processed with all functional areas in monolithic zirconia. This design offers maximum strength in functional areas. Esthetic needs are met by custom layering the facial areas using traditional zirconia layering ceramics (Figure 7 and Figure 8).
Wax-up Step Variations
As a result of the ever-increasing labor cost and the scarcity of qualified technicians able to do full-contour wax-ups, Absolute Lab utilizes a custom digitizing technique, eradicating the need for a hand wax-up of the scanning jig. By scanning the FCZ wax-up sleeve and model into our design software, we are able to design a digital tooth over the wax-up sleeve. Then, the digital design is wax milled (or wax printed) and fitted to the FCZ wax-up sleeve for scanning purposes. The normal FCZ case flow is then followed. Design software of your choice can be used for this technique (Figure 9 through Figure 12).
After processing multiple NobelProcera FCZ cases, the author continues to be amazed by clinicians’ overwhelmingly positive feedback regarding the delivery time and predictability of this product. Absolute Dental Services uses second-pour unbroken casts to establish final interproximal contacts. The author believes this process greatly contributes to the fact that Absolute’s clinicians regularly report average delivery times of 15 minute or less.
Conrad J. Rensburg, ND, NHD, is a working partner at Absolute Dental Services in Durham, North Carolina.
In case you missed it, go to the link below to read a dentist’s perspective on Nobel Biocare products.
Disclaimer: The statements and opinions contained in the preceding material are not of the editors, publisher, or the Editorial Board of Inside Dental Technology.
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