Inside Dental Technology
February 2011, Volume 2, Issue 2
Published by AEGIS Communications
Natural Esthetics from a Milling Center
The GC Advanced Technologies Milling Center provided the valuable input and information needed to achieve the desired result.
By Luke Kahng, CDT
In a maxillary six-unit anterior case, esthetics are paramount. Communication between the dentist and patient is important, but it is also crucial that the laboratory technician is comfortable with the patient’s expectations and the desired outcome. Material choice is significant, but the technician must be just as careful in deciding on which milling center to use.
A man in his mid-30s presented with the desire to change the appearance of six of his upper teeth. He was not happy with the composite bonding discoloration or the shape of his teeth, preferring a more masculine contour. The patient’s teeth were retracted to demonstrate the discoloration and shape discrepancy that had been bothering him (Figure 1).
In order to get a perfect fit and zirconia design, it is very important that the understructure supports the porcelain build-up. As the technician responsible for creating the case, the author felt that he must give the clinician a treatment planning recommendation based on what he saw. His observation was that the gingival contour was slightly under in teeth No. 7 through 10 and that tooth No. 6 was a fake crown with mismatched color. The incisal gingival contour displayed a black triangle and the color would have appeared more natural if an enamel translucency were applied. Enamel overlay changes the dentin color and decreases its overall value—important when considering the cosmetic color for an anterior restoration.
In order to get good enamel translucency color, the author used the LSK121 Chairside Shade Guide system (www.lsk121.com) for better color-matching results (Figure 2). Temporaries were created from the treatment plan wax-up and placed on the model before polishing (Figure 3) so that the patient could decide whether or not he liked them. After polishing, Paul Saniuk, DDS, placed the temporaries in the patient’s mouth (Figure 4) and received his approval. This gave the technician the green light to go ahead with his plan. A preparation view (Figure 5) demonstrates the perfect amount of room, 1 mm to 1.5 mm for an esthetic case.
Using the 3 Shape CAD/CAM scanner (www.3shape.com), the GC Advanced Technologies Milling Center in Costa Mesa, California, provided detailed information regarding full-contour and prep design with its imaging. First, the temporaries were scanned. Then the preparation, margin design, and final contouring were projected onto the model (Figure 6). This showed the technician the preparation and proper coping and frame design before the copings were fabricated (Figure 7) so he could see the inside of the coping shape he was creating.
The GC Milling Center scanner (Figure 8), where all work for this case was created, consistently provides top-quality zirconia design. The GM1000 (GCAT, www.gcamerica.com) is a high-speed, high-accuracy five-axis machine with a compact machine size and footprint. This milling unit is equipped with a work pallet system that has a capacity of 60 clinical cases, resulting in a 24-hour full automatic running. Because of its high-accuracy and ultra high-speed indexing times, cycle times during simultaneous five-axis machining are greatly reduced.
The author’s laboratory counts on the milling center to produce a final design that supports and prevents porcelain fracture, which is paramount to achieving a successful outcome. Their technicians understand full anatomy for contours as they design the framework for the author’s cases.
After sintering, the copings were tried on the die for a precise fit (Figure 9), and then checked with the soft tissue on the model (Figure 10). For esthetic purposes, the author prefers porcelain butt margins using GC Initial ZR-FS low-fusing porcelain at 840°C (Figure 11). Next, the author demonstrated porcelain dentin and enamel build-up using GC Initial ZR-FS at 810°C (Figure 12). A shade tab was used to choose appropriate colors to help complete the build-up. (Figure 13 ). After firing at 810°C, the color integrity and transparency becomes apparent ( Figure 14). The final restorations were displayed on the cast model (Figure 15) before being cemented in the mouth (Figure 16).
In order to create a perfect restoration, the three participants in the process—the dentist, the patient, and the technician—must cooperate and work as a team. But without a milling center that understands esthetics, it is much harder for technicians to complete their job accurately. A carefully selected milling center should provide the valuable input and information that technicians need to get the results they seek.
About the Author
Luke Kahng, CDT, is the owner and founder of LSK121 Oral Prosthetics in Naperville, Illinois.
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.