Straight to the Source: LMT at Pentron Ceramics
Posted Apr 28, 2011, Published 2009-03-01
For a glimpse at the current—and future—state of ceramic technology, LMT visited Pentron Ceramics, the sole porcelain manufacturer in the continental U.S.
Although not formally established as Pentron Ceramics until 2005, Pentron's roots are firmly entrenched in the history of ceramic production. Through mergers and acquisitions, the company's past is intertwined with that of American Thermocraft, a pioneer in ceramic technology.
Today, Pentron Ceramics' Somerset, New Jersey facility is the only site in the continental U.S. where dental porcelain is manufactured. LMT recently toured the 37,000-sq.-ft. building, which houses all processing, including melting, milling, blending, ingot and paste production and packaging for Pentron Ceramics brands, including Avanté®, 3G®, OPC®, Synspar®, Avanté®Z™ and the new Avanté® Press.tige™. Here's an inside look:
The Pentron Ceramics crew who welcomed LMT to its facility include (from l. to r.): Paul Panzera, vice president, manufacturing; Dmitri Brodkin, director, research and development; Donna Giordano, director of sales and marketing; Carl Panzera, chief scientific officer; and Lou Alcuri, product manager, ceramics and equipment.
Feldspar is an inexpensive, convenient source of raw material because it contains three compounds—potassium oxide, silica and alumina—that are main components of dental ceramics. (Incidentally, feldspathic porcelain is not always derived from feldspar; the term has been broadened over the years to include any porcelain containing these three components.)
Raw materials are mixed together and put into these furnaces overnight to form a glass crystal mixture. The result is a solid chunk of molten glass which is quenched in cold water, causing it to shatter into fine particles that are then placed in a mill and ground into glass powder, called frits. The powder is then put into a screen to sift out any coarse pieces. A sample from each batch of powder is fused into bars and buttons and tested for thermal expansion and translucency. The degree of translucency is actually reported as opacity, and is a measure of how much light is reflected back to the observer.
V-blenders like this one mix together anywhere from one to five types of frits, depending on the type of porcelain being manufactured. The result is a base white porcelain powder from which different shades are made. Samples from each mixed batch are again fused and tested for fusion temperature, thermal expansion and translucency. Smaller V-blenders are also used to mix pigments into the white porcelain to create shades.
Dmitri Brodkin demonstrates the Instron three-point bending fixture that tests the flexural strength of porcelain material. Other quality control tests include the dilatometer, which measures thermal expansion, and the spectrophotometer, a color measurement device. Because the spectrophotometer is not able to integrate environment and shape or distinguish between translucency and gray as the human eye can, shades are also checked by Anna Dockery, senior processing technician, who is trained and tested for her color perception.
Anna Verano (right), dental technology manager, gives LMT's Laurie Freddino, associate publisher (left), and Maribeth Marsico, senior editor, an overview of pressable technology and Pentron's new Avanté® Press.tige™ no-prep/minimal prep pressable veneer material. Capable of pressing veneers as thin as 0.3 mm, the system is designed to create a new profit center for laboratories, allowing them to obtain business from dentists who are currently using proprietary services for similar restorations.
Zirconia: A Bright Future
Two chief engineers at Pentron—who together hold more than 60 dental patents—agree with predictions that zirconia will still be king 10 years down the road.
"Ten years ago, we said we'd see less alloy used, and that's proven to be true; in another decade, we'll see even less. I also think that manufacturers will continue to enhance the strength of zirconia. Seven or eight years ago, it wasn't as strong as it is now, but it will get even better.
"It's also interesting to note that the objective of our industry's R&D efforts has changed over the years. The goal used to be to simplify materials so technicians didn't have a hard time working with them. Now the focus is on the new kids: they want techniques and materials that are more high tech, and zirconia is right up their alley." ~ Carl Panzera, Chief Scientific Officer
"I expect more of an emphasis on enhancing the translucency of zirconia. Right now there's a perception—and perception is reality in our industry—that if you opt for a stronger zirconia, you're going to get less translucency. I think you're going to see those two things come together and technicians will no longer feel that tug of war. ~ Dmitri Brodkin, PhD, Director of Research and Development
"No other material is as biocompatible and esthetic as ceramic; now, zirconia adds to the longevity. In fact, since zirconia has now been used for 10-20 years, we're approaching the time when we'll have some hard evidence that zirconia's longevity rivals that of a PFM restoration."
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