Inside Dental Technology
September 2012, Volume 3, Issue 8
Published by AEGIS Communications
The 2-CONnect Bridge
A practical choice for multi-unit, implant-supported restorations.
The initial introduction of implant-supported restorations by Dr. Branemark in the mid 1980s provided components that resulted in screw-retained restorations. At that time, there was a big emphasis on retrievability that supported screw-retained treatment plans. The technical problems in manufacturing often made it difficult to maintain the integrity of the gold cylinders (the fitting surface of the restoration) for screw-retained bridgework. Some of the loss in precision or distortion of implant components also occurred when casting, divesting, and/or soldering, as well as during continued firings in a porcelain furnace and polishing.
For the past decade, designing bridgework on implants has often included stock or custom abutment fabrication followed by fabrication of the cement-retained bridge. This treatment plan has worked quite successfully. However, the laboratory procedures used to produce the cement on restorations are difficult and labor-intensive. This, in addition to the high cost of implant components and materials, results in very costly restorations. With today’s economic climate and the competitive nature of dental technology and dentistry, it is imperative to evaluate other more cost-effective precision solutions.
With the introduction of nt-trading’s (www.nt-trading.com) FDA-approved 2-CONnect system, there are now cost-effective implant components for the 10 most popular implant interfaces. These common interfaces are available in multiple sizes. In addition, with advances in CAD/CAM, high-strength ceramics (zirconia), and the 2-CONnect system, laboratories can now streamline operations. With reduced labor, inventory, and custom parts, they can also
reduce costs. Furthermore, 2-CONnect solves problems such as achieving passive fit, lack of interocclusal space, divergent implants, retrievability, and hex-engaging complications when
2-CONnect includes a tapered 2-CONnect abutment designed specifically for each implant interface, as well as a universal titanium insert and universal final insertion screw (Figure 1). From a mechanical perspective, there are several advantages to the 2-CONnect system. First, the tapered abutment allows the divergent implants to connect up to 30º. In addition, there is no anti-rotational configuration, which improves ease of manufacturing and seating. (Please note, nt-trading also provides hexed components for single tooth replacement.) Next, there is a titanium insert that is cement-retained to the final zirconia bridge. This component is manufactured with extremely tight tolerances to insure precision fit to the 2-CONnect abutments. In addition, the titanium insert is designed to carry the load placed on the restoration by the insertion screw.
This new system can accommodate many different implant interfaces and implant bridge scenarios. The importance of passive fit for implant-supported bridgework has been known for decades. Today’s state-of-the-art CAD/CAM solutions are far more
accurate than the analog chemical-based laboratory procedures used in the past as well as the present.
Today’s dental scanners and milling machines can produce products that have very tight tolerances. For laboratories that have 3Shape (www.3shape.com) CAD/CAM capabilities, the manufacturing process is quite simple. Before beginning, it is necessary to upload the 2-CONnect library that is available from CAP, into the 3Shape system). This library provides the digital information needed to accurately design and mill a restoration that has a perfect mating surface with the 2-CONnect insert as well as abutment height calculations.
Fabricating the 2-CONnect bridge is performed through digital CAD/CAM and is quite simple.
Step 1—The analog casts are scanned using nt-trading scan bodies (Figure 2). This is done using a protocol similar to scanning implant analogs for custom abutment design. (Scan bodies are similar to impression copings.) However, the copings are scanned rather than picked up in an impression.
Step 2—CAD is performed to design an ideal full-contour, screw-retained restoration. (Those unfamiliar with the CAD process can view a 3Shape video at dentalaegis.com/go/idt57). The CAD process begins with locating the implants on the digital CAD model. Next, the transmucosal portion of the implant-supported units is designed (Figure 3). Once complete, the conventional CAD-bridge design process begins. When the restoration is fully designed (Figure 4 and Figure 5), the last step will connect all digital bridge components and place the screw access holes. From here, a STL file of the bridge is complete and sent off to the CAM software.
Step 3—The CAM software performs two essential tasks. First is nesting or placing the bridge in a digital puck (Figure 6). Part of this also includes locating connectors (or sprues) from the puck to the bridge. This is necessary so the bridge does not fall out of the puck while milling. This process requires about 1 minute of labor per unit. The second task, when the CAM calculates a milling strategy, requires no labor. This mill strategy essentially directs the spindle and puck movement, spindle speed, and chooses which tools to be used. Lastly, the
zirconia puck is placed in the mill and the milling begins. The milling process usually takes about 15 minutes per unit for full contour and 8 to 10 minutes for frameworks.
Step 4—Once milling is complete, the puck is removed from the mill, and the bridge remains connected to the puck by the sprue connectors (Figure 7). At this point, all of the automated processes are complete and the analog processing of the bridge begins. The first step is to remove the bridge from the puck. This process requires less than 1 minute of labor per unit. The zirconia bridge is removed from the puck using a fisher bur and a high-speed handpiece operating at a relatively low speed. Next, the sprues are removed from the bridge using a rubber wheel. Please note that the pre-sintered zirconia is quite soft and easily trimmed. Once all trimming is complete, the loose zirconia particulate should be dusted off.
Step 5—For pre-shading, a multi-coloring process is used to mimic the many different colors found in natural teeth. Used here was the Zirkonzahn Prettau® coloring kit (www.zirkonzahn.com) (Figure 8). Pre-sintered zirconia by nature is somewhat porous. The pores in the zirconia absorb the colorants into the material, providing lifelike
esthetics. Please note that once sintering is complete, there is no porosity in the restoration.
Step 6—The next step is the sintering cycle. Sintering zirconia is done in a specific furnace made for sintering zirconia. This requires high heat (approximately 1550º C) and the cycle runs for 6 to 10 hours. Refer to zirconia manufacturers recommendations for sintering cycle programs.
Step 7—Once sintered, there is a small amount of analog post processing. The post processing includes idealizing occlusal and interproximal contacts and possible adjustments to the final contours. For best results, a medium grit diamond should be used. Once all the re-contouring is complete, it is imperative to polish the zirconia. This is achieved with a medium grit
Step 9—Once the zirconia bridge is complete, the 2-CONnect insert is cemented in place. Panavia™ cement (Kuraray Dental, www.kuraraydental.com) was chosen to be placed on the titanium insert and the zirconia interface of the bridge. A small clamp is placed on the bridge and inserted to hold the parts in place through the cement-curing stage. Once set, all excess cement should be removed with a rubber wheel. This procedure can be done in the laboratory or by the dentist after try-in (Figure 10).
There are many technical reasons why the 2-CONnect bridge should be considered for treatment plans. First, the use of CAD/CAM versus the analog process is far more accurate and predictable. In addition, the 2-CONnect titanium parts remain in near-mint condition as they are rarely used in the manufacturing process. Once again, the reduction of many laboratory steps—such as waxing, investing, casting, and finishing metal and porcelain—dramatically reduces labor and saves valuable time. The replacement of gold alloy with zirconia is also far more cost-effective, thus dramatically reducing materials cost. The combination of increased precision, the dramatic reduction in labor, and lower materials cost are striking. Thus it is practical, logical, and effective to include the 2-CONnect system when considering treatment plans for multi-unit, implant-supported restorations.
Bob Cohen, CDT, is the president of Custom Automated Prosthetics in Stoneham, MA.
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.