ZircoStar Zirconia From Kerox
Posted Nov 20, 2013 in Technical
DENTAL TEAM: Dr. William Roddy and in-house technician Steve Coles, Flow Laboratory, Fort Worth, TX
RESTORATIVE PROBLEM: A 62-year-old female presented with implants on teeth #3, #4 and #5 and a PFM bridge placed by another dentist. The implants had been placed too far buccally and the patient was unhappy with the esthetics and thickness of the bridge. The patient's occlusal planes were also uneven, and she had another large-span anterior bridge on teeth #6 through #11 that was starting to show signs of decay at the margins.
TREATMENT PLAN: The team opted to remove both bridges and the remaining natural teeth in the arch. Additional implants were placed on teeth #6 and #11 through #14, and immediately loaded with a temporary bridge. After integration, the patient's final restoration would be a full contour, full arch, implant-supported bridge. KEROX ZircoStar zirconia in Extreme Translucent (ET) was chosen for its esthetics and ability to match natural teeth. Because of its small grain size, the material offers enhanced translucency and the ability to grind the finished bridge after final sintering if necessary.
FABRICATION PROCESS: The case was scanned using the 3Shape D700 and designed in 3Shape's CAD software. It was milled using Sum3D CAM software on a Roland DWX-50 milling machine. In a Mihm-Vogt sintering oven, Coles used a slow rate of climb—three degrees per minute—to minimize warpage and shrinkage. Putting a 30-minute hold at 900°C was important; at that temperature, recrystallization of the ceramic begins and it allowed the thicker and thinner parts of the full arch bridge to reach even temperatures.
For shading, Coles used Zirkonzahn's Colour Liquids Prettau® and let the bridge dry for 45 minutes under an infrared drying lamp. This step was critical to prevent the material from breaking in the early stages of sintering; moisture in the ceramic can abruptly transform into gas in the sintering oven and cause micro explosions, compromising the structure of the ceramic material. The restoration was completed with GC Initial stains and glaze.
CONTACT: For more information, call Tamas Rozsa at Kerox at +36 23 382 006 or visit www.keroxdental.net.
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