Inside Dental Technology
January 2012, Volume 3, Issue 1
Published by AEGIS Communications
Advanced Technique for Achieving Exceptional Esthetics
Integrating digital technologies can help create a highly esthetic and precision-manufactured single central.
Over the past decade, the dental industry has experienced a dramatic evolution in CAD/CAM technology, enabling new methods of creating restorations and designing substructures such as zirconia copings and customized implant abutments. With the addition of 3D printing technology, CAD/CAM technology can now produce dental models and wax patterns, as well as some metal substructures. Now, through advancements in 3D imaging technology, the digital impression can be expected to b come the practice standard.
As CAD/CAM and other digital technologies b come a more integral part of the dental industry, the ongoing evolution will likely pick up even more speed. Dentists and technicians should be prepared to embrace and maximize these new technologies while developing a strong, communicative relationship.
Achieving a Balance
Dental laboratories are faced with unique challenges in today’s business climate. On one hand, to maximize profitability, restorations must be efficiently produced. At the same time, increased esthetic demands from dentists and patients challenge laboratory technicians to deliver restorations with a very natural and lifelike appearance, which takes time to achieve. These conflicting objectives affect manufacturers as well. The industry is demanding tools that not only can produce sophisticated and esthetic results, but that also are simple enough to be incorporated into the laboratory productively and profitably. While the trend toward increased digitization does remove some of the demands from the technician’s shoulders, it also necessitates a new skill set in order to manage the tools properly to ensure form, fit, function, and esthetics of the restorations.
New restorative options are being introduced to help the industry balance these competing demands. Among them are automated alternatives to traditional hand-layered and pressed ceramics. Systems such as Ivoclar Vivadent’s CAD-on (www.ivoclarvivadent.com) and 3M ESPE’s Lava™ DVS System (www.3mespe.com) allow milling of two components—a zirconia substructure, as well as a porcelain or lithium-disilicate veneer. After milling, the technician applies fusion porcelain inside of the veneer to fuse it to the substructure. The two pieces are then fired together, and the technician finishes the piece by touching up and glazing it. Technicians can use a variety of shades, stains, fusion porcelain powders, and corrective porcelain powders to customize each component of the restoration.
In the case presented, the author used the 3M ESPE Lava™ Design software to create an anatomically shaped zirconia coping that properly supports the milled porcelain veneer. The software automatically generates the two milled components of the restoration in the proper proportions, which offers laboratories significant time savings. With the help of technology, laboratories can efficiently allocate staff time with less experienced technicians assigned to produce the restorations, while experienced technicians complete the finishing touch-ups and glazing according to the desired standard. The author has found that technology actually provides a unique opportunity for ceramists to demonstrate their esthetic skills. In this way, the system helps combine both productivity and artistry in a manner that will only b come more vital as time goes on.
To achieve the increased esthetic demands of patients, the authors have developed a patent-pending technique of a Lava DVS Crown. The technique centers on modifying the inside wall of the veneer, which allows a ceramist to add translucency and color to create increased depth and greater characterization. The technique was developed based on the author’s knowledge of the classic tooth dissection photography of Claude Sieber, which demonstrated the relationship between the layers of the tooth and the way in which color is imparted. The author’s own photography has influenced the technique as well, providing knowledge of the interaction between natural enamel and light (Figure 1).
As technicians know, in a natural tooth a thin slice of translucent structure is sandwiched between enamel and dentin, which discolors with age. This internal structure is responsible for much of the characterization and color of natural teeth. Therefore, it makes sense for the dental technician to turn his or her attention to the internal surfaces of a restoration when possible. With this approach, the laboratory’s results can more precisely approximate nature. When using pressed-to-zirconia or pressed-to-metal materials, however, modifications can only be performed on the substructure. The advantage of this system is that it gives ceramists the ability to modify the internal wall of the veneer.
Using these steps, ceramists may be surprised at the level of customization that is possible with full-contour milled crowns. Even accounting for the additional steps of the advanced technique, the process is faster than hand stacking porcelain. It also results in restorations with exceptional esthetics, satisfying the laboratory’s need for both productivity and outstanding quality.
The patient, a 62-year-old man, presented to the dental office after fracturing the CEREC® crown (Sirona, www.sirona.com) that had been placed on tooth No. 8, which had fractured 6 years prior (Figure 2). At the time of initial treatment, a root canal had been performed and a post-core placed in the tooth. The latest fracture, however, broke the tooth at tissue level. The treating dentist placed a temporary crown and prescribed a Lava crown for the final restoration.
At the laboratory, the model was poured and the case was digitized using the Lava™ Scan ST Design System (3M ESPE). Once the scanned preparation was imported into the software, the technician marked the margins of the restoration and made other adjustments to the full-contour design. The software then automatically generated the designs for the coping and veneer in the proper relation (Figure 3, Figure 4, Figure 5 and Figure 6). After the sprues were digitally placed, the case was sent to a Lava Authorized Milling Center for production (Figure 7).
Once the components arrived back in the laboratory, the coping was checked for fit on the solid model (Figure 8). After confirming the fit, a small amount of material was removed from the inside of the coping using a slow-speed straight handpiece. Creation ZI-F shoulder porcelain (Jensen Dental, www.jensendental.com) was applied to the internal surface of the coping (Figure 9). The coping was then fired according to the porcelain manufacturer’s r commendations (Figure 10). Lava DVS stain in shade S3 was then applied to the neck of the coping and the incisal tip to create a more saturated color (Figure 11).
Work then turned to the veneer. A slow-speed straight handpiece was used again to modify the internal surface of the veneer to create room for porcelain (Figure 12 and Figure 13). A sharp surgical knife was used to create crack lines in the veneer to mirror the appearance of the patient’s left central incisor. White stain was then painted into the crack lines (Figure 14). Once all the necessary staining had been performed, the veneer was fired in the furnace at 610°C to 630°C to set the stain in place. Note: Firing temperatures will vary according to individual furnaces. Follow the manufacturer’s r commendations.
Lava DVS Corrective Porcelain Powder in shade CR3 was then applied to the coping and the interior surfaces of the veneer (Figure 15). This was applied in place of the r commended fusion porcelain, due to the high translucency of the patient’s natural teeth. The veneer was seated onto the coping, and the restoration was fired according to instructions to fuse the two components together (Figure 16, Figure 17 and Figure 18). A final round of characterization was performed with the application of CR2 and CR3 corrective porcelain powder, as well as Creation ZI-F powder, and the restoration fired for the last time (Figure 19). Final finishing steps were completed and the crown was delivered to the dentist (Figure 20). Upon placement in the mouth, the esthetic match was evident, and the patient was extremely pleased with the results (Figure 21).
As seen in this case, there are a number of ways in which ceramists can perform this technique for Lava DVS crowns. The system, therefore, presents opportunities to both well-seasoned and less-experienced technicians. In fact, much of the work in this case was performed by an employee who is not a long-time technician.
Past experience has shown that any ceramic material must satisfy a wide spectrum of ceramists to be successful. Those that are too simplistic will not interest the advanced technician, and materials specifically designed for the advanced technician may not have a broad enough market to survive. The same situation can be seen with dental composite materials. In both instances, materials must be versatile enough to appeal to professionals at all points on the spectrum—experienced and inexperienced.
As shown by this case, even on a tooth as esthetically sensitive as a single central, digital and automated tools can play an important role in efficiently and accurately creating the restoration. To move into the future, laboratories must examine the opportunities available to them that can help increase productivity without sacrificing appearance. In many cases, this will require thoughtful integration of the time and expertise of both highly skilled and less experienced laboratory technicians. This case demonstrates that in the hands of advanced ceramists, or under their guidance, this technology can be used to efficiently create restorations with exceptional esthetics.
About the Authors
Sang Jun, CDT
Bay Dental Laboratory
Kevin K. Lee, PS
Bay Dental Laboratory
Brian Lackey, DDS
Pacific Grove, California