How to Fabricate an 11-Unit Zirconia Bridge Using a Manual Milling System Case Study Restorative Challenge A female patient lost teeth #2-5, 7, 10 and 13 to dental caries and periodontal disease. She presented with a faulty 11-unit bridge with open margins, a reduced occlusal vertical dimension and faulty pontic design, especially in the areas of teeth #10 and 11 (Figures 1 and 2). She wanted a more esthetic and functional bridge. Restorative Team Alexander Kanotscher, CDT, owner, Zahnprofi in Braunau/Inn, Austria and Dr. Wolfgang Koller from Scharding, Austria. After the faulty bridge was removed and the teeth re-prepared, a temporary bridge was fabricated. This case was challenging, as the center line between the upper and lower anterior teeth didn’t match and the patient presented with asymmetry of the upper lip. Dr. Koller sent the impressions to Zahnprofi where stone models were fabricated (Figure 3). Using the Zirkograph 025, Kanotscher milled a trial framework made from a sturdy light-cured resin on the articulated working model. The benefit of milling a trial framework is that all the necessary adjustments can be made to the resin framework and then it can be exactly replicated in zirconium, saving material costs and reducing the need for remakes. Kanotscher gave special attention to the condylar paths to ensure proper function and created a cuspsupported substructure to ensure a uniform thickness of ceramic to prevent fractures. He returned the framework to Dr. Koller for a try-in and provided removable acrylic facings for verification of esthetics and phonetics (Figure 4). These facings are easy for the dentist to use and can be adjusted chairside using traditional grinding equipment or added to with a light-cured polymer at try-in. Internal corrections of individual abutments can be made, edges checked and a bite registration taken with the plastic framework in situ. Dr. Koller returned the adjusted resin framework and bite registration to the laboratory (Figures 5 and 6). Kanotscher inserted the resin framework into the Zirkonzahn milling unit. Using a single blank of zirconia in the appropriate size for the case, Kanotscher copy milled the case (Figures 7 and 8). The five-axis Zirkograph 025 enabled him to mill out the 11-unit framework as one piece with excellent detail. To compensate for the shrinkage of the zirconia during sintering, the Zirkograph 025 automatically increases the size of the coping during milling. Treatment Plan Kanotscher and Dr. Koller decided to build an 11-unit zirconia bridge to replace teeth #4-14; tooth #4 was included in the bridge as a cantilever crown and teeth #2 and 3 were not restored. The bridge would be processed and milled using the Zirkograph 025 manual zirconia milling system from Zirkonzahn. The patient presented with a faulty 11-unit bridge. Pontic areas of teeth #10 and 11 were defective and the patient’s smile was asymmetrical. Stone model of newly prepared abutment teeth. Acrylic framework for try-in with removable plastic acrylic facings that can be used to verify esthetics and phonetics. The milling process took Kanotscher about 90 minutes. After he was done, he removed the zirconia structure from the system and dipped it into an A3 color liquid. The structure then was pre-dried under an infrared light and sintered (Figure 9). Lab Management Today November/December 2008 Although an overlay of veneering porcelain is optional, it was used in this case for better preservation of opposing natural dentition since the zirconium is so hard. The dentist placed the final bridge and verified that it was fully seated using radiographs. Both the dentist and the patient approved the esthetics and final shade of the bridge before it was cemented. The patient is very pleased with the esthetic results, especially because there’s no metal margin, blue discoloration to the gingival or shadows. (Figures 10-13). Kanotscher’s Buying Decision Bite registration taken in cement. The edges of the crowns are checked for accuracy. The resin coping in the template disk. Like many laboratory owners, Alexander Kanotscher, CDT, owner of Zahnprofi in Braunau/ Inn, Austria, began outsourcing zirconia copings and frameworks to respond to client demand. After outsourcing for three years, his outsourcing costs began to rise and he started looking for a zirconia milling system to gain more control over his product in his four-person laboratory. In February 2005, Kanotscher purchased Zirkonzahn’s Zirkograph 025 milling system developed by owner Enrico Steger of South Tyrol, Italy. It’s a manually operated, copy milling system that can fabricate zirconia crowns, bridges up to 14 units, dowel crowns, posts and cores, long-term temporary appliances, inner telescopes, anchor and attachment work, Maryland bridges and implant superstructures. It can mill all types of preparations and, because of its five-axis milling, it can handle bridges with diverging abutments. Since purchasing the system, Kanotscher’s lab has increased its sales by 20% each year and it’s now an outsource provider for other laboratories. “I like the manual aspect of the system because I can offer a precise zirconia restoration without being dependent on expensive equipment and I don’t have the corresponding maintenance costs. Also, I like the control I have with the system,” says Kanotscher. The sintered bridge. Alexander Kanotscher, CDT, owner, Zahnprofi, mills the bridge using the 5-axis Zirkograph 025. Material Values of ZirkonZahn’s ZrO2 Bending strength of Zr02: 1200 Mpa (in comparison, the bending strength of glass ceramic is 100-200 Mpa) Palatal view of the bridge mounted on the stone model. Buccal view of the bridge mounted on the stone model. Hardness: 1250 Vickers Fracture Toughness: 10-12 Weibull Radioactivity measurements: Zr02 single unit: 0.3 Bq Facing ceramic: 1 Bq Adult human body: 6,000 Bq Contents for this article provided by Zirkonzahn The bridge cemented in patient’s mouth. The patient is very pleased with the esthetic results of her new bridge. Zirkonzahn introduced the Zirkograph 025 manual milling system to the U.S. market in 2007. The system price starts at $5,425; if you have additional questions, call 800-989-8931 or 678-441-9419, e-mail [email protected] com or visit www.zirkonzahn.com.
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