Inside Dental Technology
April 2013, Volume 4, Issue 4
Published by AEGIS Communications
The Izir™ All-Ceramic, Hybrid-Type, Screw-Retained Restoration
Find cost savings by eliminating custom or stock abutments from the process
Today many patients have the need for implant-supported prosthetic devices that replace teeth and create an illusion of soft tissue. Through significant advancement in material science, computer technology, and CAD/CAM, it is now possible to provide high-strength restorations that will provide many years of predictable function which are cost-effective, passive-fitting, and highly esthetic.
The Izir™ all ceramic (zirconia) hybrid-type restoration from Custom Automated Prosthetics includes a combination of implant therapy and CAD/CAM technology. Implants should be placed using a guided surgical procedure. Once the patient is ready for prosthetic treatment, the restorative dentist obtains a conventional implant impression, opposing model, and a diagnostic cast. Model fabrication is performed using soft tissue material, analogs, and low-expansion die stone. If the diagnostic cast is not an adequate representation for planning the final restoration, the case should follow a denture setup and try-in protocol to establish all case design parameters.
The design can be submitted to the laboratory with either a diagnostic cast or denture setup. The case data entry is uploaded to the 3Shape case manager (www.3shape.com) for a PMMA provisional with the 2-CONnect library interface, and the models are scanned using a 3Shape D800 scanner. In addition, the denture setup or diagnostic cast is scanned so that it may be used for designing the restoration. The CAD procedure requires the designer to go through several steps to obtain the final PMMA design (Figure 1). The goal is to replicate the design of the denture setup or diagnostic cast that was scanned. The only necessary design change is to remove contour to allow space for an application of pink material to replicate the soft tissue. Once complete, a PMMA provisional is milled. This is followed with some post-processing and the addition of pink acrylic to the cervical area to mimic the appearance of soft tissue and duplicate (from the wax-up) the appropriate tooth length. A final polish can be accomplished using conventional acrylic polishing methods (Figure 2). The final steps include fastening the 2-CONnect cylinders to the provisional using primer and resin cement.
The 2-CONnect abutments are then seated back in the patient’s mouth. Next, the provisional is placed in the mouth to verify the fit of the restoration, which confirms the accuracy of the previously obtained impression and analog model.
The patient and dentist can now assess the vertical, esthetics, hygiene, speech, and function of the provisional (Figure 3). If the original design of the provisional is properly confirmed for all the design elements, then the final case construction can begin. The dentist can make note of all small modifications needed and return the models to the laboratory for fabrication of the final restoration.
If the provisional requires moderate or more than moderate adjustments, the provisional (after modification), along with the models, should be returned to the laboratory with the 2-CONnect abutments and screws. Now the laboratory can scan the adjusted provisional as a new wax-up. In addition, the original data used for designing the PMMA temporary is uploaded from the 3Shape dental manager. The data entry for the product type is changed to zirconia full-contour screw-retained. If the CAD design needs alterations, the CAD operator can quickly alter the original STL file that was previously designed for the PMMA provisionals.
The design file is loaded into the CAM software (SUM3D, www.sum3ddental.com) and placed in a virtual zirconia puck. Using the CAM, careful attention to sprue placement and sintering block design is completed. Once achieved, the CAM program will proceed with a calculation process and milling of the green state CAP FZ Full Contour Zirconia in a Roland DWX-50 (www.rolanddga.com).
Once the milling is complete the green state milled restoration and sintering block are carefully removed from the puck. Green state zirconia is quite soft when compared to other materials found in dental laboratories, and as a result, the rotary instruments used for green state finishing are unique to green state zirconia finishing. At this time, the technician should do the entire final contour detailing of the restoration (Figure 4).
Once the bridge is contoured to final form, the restoration is cleaned with a brush to remove all loose zirconia particulate. By nature, green state zirconia is absorbent, thus adding colorants to the green state restoration will enable a multi-shaded restoration. Like natural teeth, zirconia can be fabricated with multiple intrinsic shades (Figure 5). After drying, the bridge is placed in a sintering furnace that runs a 10-hour sintering program.
Grinding sintered zirconia should be as limited as possible. The technician can make small alterations with rotary high-speed diamond instruments and irrigation.
For a lifelike final product, the bridge is polished and subsequent stain and glaze with GC Initial™ Lustre Pastes (GC America, www.gcamerica.com) (Figure 7). The final step requires cementing the 2-CONnect titanium caps into the bridge (Figure 8). The cementing process is achieved with Multilink Implant Adhesive (Ivoclar Vivadent, www.ivoclarvivadent.com) and the restoration is inserted (Figure 9).
The Izir restoration is supported by an automated workflow with materials that are economical. As a result, Izir can be fabricated very predictably as a cost-effective solution.
About the author
Bob Cohen, CDT, is the president of Custom Automated Prosthetics in Stoneham, Massachusetts.
For more information, contact: Custom Automated Prosthetics
Disclaimer: The preceding material was provided by the manufacturer. The statements and opinions contained therein are solely those of the manufacturer and not of the editors, publisher, or the Editorial Board of Inside Dental Technology.